This publication is a summary of a workshop held on March 8, 2019 in Portland, Oregon. The project was sponsored with funding from the Extension Implementation program of the National Institute of Food and Agriculture, U.S. Department of Agriculture, with cofunding from the Oregon Mint Commission. The “IPMSP” format is research in progress.
Katie Murray, statewide IPM coordinator, Oregon IPM Center, and assistant professor of practice, Department of Environmental and Molecular Toxicology; Darrin Walenta, Extension agronomist and associate professor, cropping systems pest management; Paul Jepson, professor, Oregon IPM Center, Department of Environmental and Molecular Toxicology, and Isaac Sandlin, faculty research assistant, Oregon IPM Center, all of Oregon State University.
In a proactive effort to identify pest management priorities and lay a foundation for future strategies and increased use of integrated pest management (IPM) in mint production, growers, commodity-group representatives, pest control advisors, processors, university specialists and other technical experts from the mint industry in Oregon, Washington and Idaho formed a work group and assembled this plan. Members of the group met for one day in March 2019, in Portland, Oregon, where they discussed and reached consensus about IPM priorities and opportunities. The plan outlines major pests, current management practices, critical needs, activity timetables and efficacy ratings of various management tools for specific pests in mint production. The result is a strategic plan that addresses many IPM and pest-specific critical needs for the Pacific Northwest mint industry.
A list of top-priority critical needs was created based on a group-voting process at the work group meeting. This was drawn from an assessment of all the needs that appear throughout the document, which were compiled based on input from work group members. A list of broader IPM needs was also compiled to address broader, less pest-specific barriers to IPM adoption. Crop-stage-specific critical needs are also listed, and discussed throughout this publication.
This strategic plan begins with an overview of mint production. The overview is followed by discussion of critical production aspects of this crop, including the basics of IPM in mint production in the Pacific Northwest. Each pest is described briefly, with links provided for more information about the pest’s biology and life cycle. Within each major pest grouping (insects, diseases and weeds), individual pests are presented in alphabetical order, not in order of importance. The remainder of the document is an analysis of management practices and challenges organized by crop life stage in an effort to assist the reader in understanding whole-season management practices and constraints. Current management practices are presented using a “Prevention, Avoidance, Monitoring, and Suppression” (PAMS) framework to place practices within a simple IPM classification and to demonstrate areas where additional tools or practices may be needed. For more information, see Appendix F, “Using PAMS Terminology” (page 58).
Trade names for certain pesticides are used throughout this document as an aid for the reader. The use of trade names in this document does not imply endorsement by the work group or any of the organizations represented.
Travis Boyd, Aromatics, Inc.
Lisa Brain, consultant, Agrimanagement Inc.
Devin Dekker, Buyer, RCB International
Will Jessie, Extension, Oregon State University
Mark Nelson, Buyer, AM Todd
Bryon Quebbeman, consultant
John Reerslev, grower
Steve Salisbury, Mint Industry Research Council
Betsy Verhoeven, Extension, Oregon State University
Darrin Walenta, Extension, Oregon State University
Doug Walsh, IPM Coordinator, Washington State University
Tony Weitz, grower
Paul Jepson, Oregon State University
Katie Murray, Oregon State University
Isaac Sandlin, Oregon State University
Jeremiah Dung, Extension, Oregon State University
A similar plan was developed for mint in 2002. The following needs were identified by the 2002 workgroup as “most critical.” An update on current progress, reported by the 2019 workgroup, follows each item.
The following critical needs were voted as the “top-priority” needs by the work group members present at the February meeting. Crop-stage-specific aspects of these needs, as well as additional needs, are listed and discussed throughout the body of the document. Note that the order of appearance within these lists does not reflect an order of importance.
Mint is a perennial crop, grown mainly for its oil, which is used as a flavoring in chewing gum, dental products, and other confectionery and pharmaceutical products. The United States is the largest producer of peppermint oil and spearmint oil in the world. The Pacific Northwest region of the United States (Oregon, Washington, and Idaho) is the center of U.S. mint production, accounting for about 80% of U.S. peppermint acreage, and 63% of U.S. spearmint acreage. In 2018, the Pacific Northwest harvested 43,500 acres of peppermint, which yielded an average of 104 pounds of oil per acre. Approximately 14,500 acres of spearmint were harvested, yielding an average of 148 pounds of oil per acre.
Table 1: Mint Oil: Harvested acres, oil yield and U.S. ranking, 2018 crop year; data provided by the Mint Industry Research Council.
|
Peppermint |
Spearmint |
|||||
|
Harvested acres |
U.S. acreage (%) |
Oil yield (lb./A) |
Harvested acres |
U.S. acreage (%) |
Oil yield (lb./A) |
|
|
Washington |
13,000 |
24% |
117 |
11,400 |
51% |
154 |
|
Oregon |
13,500 |
25% |
88 |
1,600 |
7% |
113 |
|
Idaho |
17,000 |
31% |
106 |
1,050 |
5% |
139 |
|
Pacific Northwest |
43,500 |
80% |
104 |
14,050 |
63% |
148 |
|
U.S. |
54,000 |
22,200 |
||||
Washington leads the United States in total mint production, with 13,000 acres of peppermint and 11,400 acres of spearmint. Washington accounts for more than half of the U.S. spearmint acreage, producing both native and Scotch spearmint. Mint production in Washington is concentrated in the central part of the state east of the Cascade Mountains, in the Columbia Basin area. Counties that grow mint include: Adams, Benton, Franklin, Grant, Kittitas, Lincoln and Yakima. Mint is also grown in Clark County, which is on the west side of the Cascade Mountains.
Idaho ranks second for U.S. mint production and first for peppermint production, with approximately 17,000 acres of peppermint and over 1,000 acres of spearmint in production. Mint production in Idaho is primarily in the southwestern part of the state, with most of the acreage located in Ada, Canyon, Elmore, Gem, Owyhee, Payette, Twin Falls and Washington counties.
Oregon ranks third for U.S. mint production, with approximately 13,500 acres of peppermint, and 1,600 acres of spearmint harvested in 2018. About a quarter of the production occurs in the moist and moderate Willamette Valley on the west side of the Cascade Mountains and the other three quarters of the production is on the east side of the Cascade Mountains, where summers are warmer and drier and winters are cold. Counties west of the Cascade Mountains that grow mint include Benton, Clackamas, Columbia, Lane, Linn, Marion, Polk and Yamhill. Central and eastern Oregon counties that produce mint include Baker, Crook, Deschutes, Harney, Jefferson, Klamath, Lake, Malheur, Morrow, Umatilla, Union and Grant.
All commercially grown mint is dependent upon environmental and physical factors, including temperature, day length and soil type. The long day length north of the 45th parallel triggers flowering and oil production responses in the mint plant, and the sunny days ensure lush foliage for high amounts of hay from which to extract mint oil. Mint requires warm days (85–95° F) and cool nights (55–60° F) for optimum growth. The differences in environmental and physical factors among the various growing regions in the Pacific Northwest are responsible for the distinctive differences in mint oil characteristics and yields between regions.
Most of the mint-growing regions of the Pacific Northwest are semiarid and require irrigation for optimum production. The water requirements for a good mint crop are from 30 to 40 acre-inches per year. Mint is grown on a variety of soil types, but soils with good drainage, a pH of 6.0–7.5, and high organic matter are best suited for mint production. Fertilizer is an integral part of mint production, and most mint requires up to 250 pounds per acre of nitrogen fertilizer per acre per season.
The crop is established by transplanting either greenhouse-grown plants in the spring or field-grown roots in the fall. Greenhouse-grown plants are usually planted in the spring, in rows 40 inches apart, with total plant populations of about 10,000 per acre. Over the course of the first summer, stolons spread between rows to create an established stand. The crop is then swathed, chopped and distilled to extract the oil when it begins to bloom in the summer. If planted in the fall, field-grown roots are transplanted in 20-inch rows.
Mint can be harvested once or twice, depending on the variety and location. A single harvest is referred to as “single-cut” mint. Some varieties are allowed to regrow through the summer after the first harvest, then harvested again. This practice refers to “double-cut” mint. Most spearmint (particularly native spearmint) and some peppermint acreage is harvested twice, depending on the production region and the needs of mint oil processors.
About a quarter of the acreage in Idaho is double-cut, along with most of the eastern Washington acreage. Fields irrigated with overhead sprinklers are commonly double-cut.
Eastern Oregon acreage is mostly single cut, as is the majority of Willamette Valley acreage.
Commercial mint production in the Pacific Northwest started around 1920, and mint has since served as an economically important perennial crop. As a mint field matures over time, it becomes increasingly susceptible to insects, diseases and weeds, all of which can have negative impacts on oil yield and quality. Pest infestation can build to excessive levels that significantly weaken a mint stand, resulting in economic loss. Complete economic loss can occur if the field has to be removed from production too early in the rotation cycle.
The first step in mint IPM is to prevent the introduction of diseases, insects and weeds into a new field. This can be achieved through planting pest-free rootstock, followed by thorough sanitation of equipment when moving between fields. General crop management practices that emphasize planting disease-free rootstocks, good soil sanitation and tilth, plant vigor, irrigation scheduling and frequent monitoring (scouting) fields for soil moisture, plant health, pests and beneficial arthropods are key for optimizing oil yield.
Agrochemicals are also important tools for effective pest management in mint production. Decision-support tools such as the Oregon mint pest alert system (http://blogs.oregonstate.edu/mintpestalert/); USPest.org and the Integrated Pest Management on Peppermint 3.0 web site (http://uspest.org/mint/) ; and the Pacific Northwest Pest Management Handbooks (https://pnwhandbooks.org/) facilitate judicious use of these compounds when needed. Mint IPM is based on a continuous effort to identify effective pest management options that include cultural, biological, chemical and genetic techniques that enable long-term economic and environmental sustainability.
Numerous insect pests can thrive in mint production fields and pose a year-round threat to crop health. Although some variation in seasonal impacts may occur depending upon the pest species and production area, major spring insect pests in mint include cutworms, armyworms, symphylans and mint stem borer. Summer insect pests include spider mites, cutworms, loopers and mint root borer. Post-harvest or fall active insect pests include mint root borer, symphylans, cutworms and root weevil larvae.
Insecticides remain a key management tool for mint insect pests of economic concern. The recent development and registration more pest-specific and biologically based pesticide compounds has reduced reliance upon broad-spectrum pesticides. Chlorantraniliprole (Coragen) is an example of a new, target-specific insecticide that provides effective control for several larval pests on peppermint (including mint root borer, cutworm, armyworm and looper), and has the added benefit of low toxicity to beneficial insects. This compound also offers a dual-application window, either as a pre- or post-harvest application.
A diverse community of beneficial insects inhabits many mint fields and can have suppressive effects on pest insect populations. Examples of natural enemies include parasitic wasps, syrphid flies, lady beetles, predator mites, lacewings, big-eyed bugs and spiders. However, in-field levels can change in favor of pest populations due to management practices, weather, insecticide applications, etc., and overcome the ability of natural enemies to fully suppress pest populations. In spite of this, natural enemies still play an important role, and IPM programs must strive to protect and enhance populations. Although spider mites can sometimes be a major pest in mint, predator mites naturally occurring in the field can maintain spider mite populations at a low enough level to delay or avoid the need for miticides. Insecticide applications against other target pests can disrupt natural enemies, leading to an outbreak of secondary pests, including spider mites. In situations where spider mite populations exceed thresholds, pest control compounds are chosen to minimize impact on predator mite populations.
Several diseases in mint are caused by fungal pathogens. Verticillium wilt ( ) is a soil-borne fungal pathogen considered to be the most significant threat to mint production. Over time, disease inoculum in wilt-infected fields can increase to levels that prevent mint growth. The disease survives for years in the soil as microsclerotia, and thus, long rotation cycles out of mint are required to reduce soil inoculum.
Management for verticillium wilt is limited mainly to cultural techniques deployed prior to planting a new stand of mint. However, flaming the field after harvest is used in some production areas to reduce inoculum in post-harvest residue. In fields with a history of verticillium wilt but with at least five years out of mint production, some growers fumigate before planting, and then plant certified-disease free rootstock of an improved cultivar. Soil fumigation provides the added benefit of managing plant-parasitic nematodes. Severely infected fields may require rotation cycles out of mint production for up to 10 years in an effort to reduce soil inoculum levels below economic injury levels. Fields with no history of mint production are ideal candidates for planting with certified disease-free rootstock.
Native spearmint is relatively resistant to verticillium wilt, whereas, Scotch spearmint and Black Mitcham peppermint are susceptible. Only a few improved peppermint cultivars are currently available that exhibit low to moderate levels of resistance to verticillium wilt. New peppermint production fields are often planted with state-certified Verticillium-free rootstock produced from certified propagation materials sourced from the Mint Industry Research Council or state-certified field rootstock propagation programs.
Mint fields are highly susceptible to weed infestations, especially during the year of establishment and before the crop canopy closes. Weeds impact both the yield and quality of mint oil with varying levels of impact based on the weed species present and level of infestation. Weeds can also become hosts to insects and diseases that can become economically damaging.
Weed management for new mint fields focuses on crop rotation, cultivation, seed-bed and root-stock preparation, and properly timed herbicide applications. In established stands, weed pressure can increase over time even with the use of herbicides, which requires the investment of additional hand-labor to remove the infestations prior to harvest Problematic annual weeds (common groundsel, pigweed, mayweed and prickly lettuce) and persistent perennial weeds (field bindweed) are difficult to control, and infestation levels build over time if management efforts are not successful.
Successful weed IPM relies on frequent monitoring of fields, early management decisions, and integration of multiple management tactics.
The following list of broad IPM needs was compiled based on input from workgroup members. Participants were asked to identify specific needs related to each of the headings in bold. Specific needs appear as bulleted lists below.
(listed alphabetically)
Alfalfa looper (Autographa californica)
Aphid (Ovatus crataegarius)
Armyworm (Mamestra configurata)
Cabbage looper (Trichoplusia ni)
Mint cutworm (Heliothis phloxiphaga)
Spotted cutworm (Amathes c-nigrum)
Variegated cutworm (Peridroma saucia)
Garden symphylan (Scutigerella immaculata)
Clearwinged grasshopper (Camnula pellucida)
Lygus (Lygus spp.)
Mint flea beetle (Longitarsus waterhousei)
Mint root borer (Fumibotys fumalis)
Redbacked cutworm (Euxoa ochragaster)
Root weevil (Otiorhynchus sulcatus)
Slug (Deroceras reticulatum)
Spider mite (Tetranychus urticae)
Thrips (Frankliniella spp.)
Wireworm (Limonius spp.)
Black stem rot (Phoma strasseri)
Leaf blight (Cephalosporium sp.)
Needle Nematodes (Longidorus elongatus)
Pin Nematodes (Paratylenchus spp.)
Root-knot Nematodes (Meloidogyne hapla)
Root-lesion Nematodes (Pratylenchus penetrans)
Phoma (Phoma sp.)
Powdery mildew (Golovinomyces biocellatus)
Stolon decay and canker (Rhizoctonia solani)
Verticillium wilt (Verticillium dahlia)
Rust (Puccinia menthae)
Barnyard grass (Echinochloa crus-galli)
Little bittercress (Cardamine oligosperma)
Annual bluegrass (Poa annua)
Wild buckwheat (Polygonum convolvulus)
Canada thistle (Cirsium arvense)
Catchweed bedstraw (Galium aparine)
Common chickweed (Stellaria media)
Common dandelion (Taraxacum officinale)
Cheatgrass (Bromus tectorum)
Field bindweed (Convolvulus arvensis)
Filaree (Erodium spp.)
Flixweed (Descurainia Sophia)
Green foxtail (Setaria viridis)
Common groundsel (Senecio vulgaris)
Horseweed (Conyza canadensis)
Prostrate knotweed (Polygonum arenastrum)
Kochia (Bassia scoparia)
Common lambsquarters (Chenopodium album)
Black nightshade (Solanum americanum)
Hairy nightshade (Solanum physalifolium)
Yellow nutsedge (Cyperus esculentus)
Pineappleweed (Chamomilla suaveolens)
Powell amaranth (Amaranthus powellii)
Prickly lettuce (Lactuca serriola)
Puncturevine (Tribulus terrestris)
Quackgrass (Elymus repens)
Rattail fescue (Vulpia myuros)
Red orach (Atriplex hortensis)
Redroot pigweed (Amaranthus retroflexus)
Russian thistle (Salsola ssp.)
Italian ryegrass (Lolium multiflorum)
Common salsify (Tragopogon porrifolius)
Shepherd’s-purse (Capsella bursa-pastoris)
Red sorrel (Rumex acetosella)
Annual sowthistle (Sonchus oleraceus)
Tumble mustard (Sisymbrium altissimum)
Witchgrass (Panicum capillare)
Bladder campion (Silene vulgaris)
Nightflowering catchfly (Silene noctiflora)
Cinquefoil (Potentilla supina)
Mint stem borer (Pseudobaris nigrina)
Nematodes, symphylans, verticillium wilt, weeds
Cutworms, weeds
Cutworms, weeds
Aphids, caterpillars, cutworms, loopers, mites, mildew, root borer, root weevil, nematodes, symphylans, rust, weeds
Armyworms, cutworms, root borer, nematodes, symphylans, weeds
Weeds
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-aphid. Wingless forms of aphid are apple green to yellow-green. Winged forms have a dark brown head and thorax. Large populations can stunt and distort stems and leaves, make plants more susceptible to water stress, and secrete honeydew, which can lead to sunburned leaves or result in leaves covered with black, sooty mold.
Bertha armyworm (Mamestra configurata)
Mint cutworm (Heliothis phloxiphaga)
Spotted cutworm (Amathes c-nigrum)
Variegated cutworm (Peridroma saucia)
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-armyworm-cutworm
Variegated cutworm larvae are brownish, with white marks on each dorsal (top) abdominal segment. Bertha armyworm larvae are highly variable, from uniform pale green to black with fine longitudinal yellow lines. Mint cutworm are large, yellow, tan or green larvae with black spots over the body, similar to corn earworm. Spotted cutworm larvae vary in color, but most are dark brown to black, with distinct markings on the back. Damage is similar to that of the variegated cutworm and alfalfa looper, but this insect is seldom a problem of economic importance on mint. Larval feeding on leaves in late June, July, and August can reduce oil yield.
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-garden-symphylan
Garden symphylans are small (less than a quarter inch), white, centipede-like animals that feed on the hairs and tissue of roots and underground stems. Heavy feeding causes plant stunting, poor stem elongation and small, chlorotic leaves. This insect is a very serious pest of many crops in western Oregon where there is a long history of only partially successful control methods.
Populations build rapidly in spring and summer, and usually decline from late summer through fall as soil temperatures rise and moisture content drops. Populations build again in the fall with rains, and can cause damage to roots in mild winters.
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-grasshopper
Grasshoppers feed on leaves throughout spring and summer. Leaf loss can be significant in years with warm, dry conditions in the spring.
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-alfalfa-looper-cabbage-looper
Alfalfa looper (Autographa californica)
Cabbage looper (Trichoplusia ni)
Looper larvae are pale green with white lines on backs and sides. Larvae have three pairs of abdominal prolegs, whereas cutworms and armyworms have five pairs. Larvae move in a “looping” manner. The adult looper is a gray-brown moth with U-shaped spot on forewings.
In the Willamette Valley, damage during the early season (May and early June) may appear serious. However, the plant almost always repairs the damage by harvest. This generation can be heavily parasitized by natural enemies, which reduces potential for late-season damage from this pest.
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-mint-flea-beetle
The main damage is by the flea beetle larvae, which feed on and severely damage roots in late April, May and June. However, the small, pale brown to brownish-yellow adult flea beetles feed on mint foliage, producing “shot-holed” leaves.
Because of the potential for damage, they usually are treated when detected (early July).
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-mint-root-borer
This pest is present and can severely reduce stands in most mint-producing areas. Larvae are white with a brown head. They feed inside mint rhizomes and on mint roots, from late July through September and early October in some years.
This pest overwinters in the soil around mint roots as a prepupa in a cocoon, pupates in the spring, and emerges as a moth in June and July. There is one generation per year.
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-mint-stem-borer
Mint stem borer is a small white grub, 0.08 to 0.16-inch-long, with a brown head and no legs. Damage is caused to the main root, leading to injury or death to the central stalk, which usually breaks off. It is found in eastern Oregon and Idaho. This pest can infest mint rootstock for export. It is also suspected by some as a possible disease vector.
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-redbacked-cutworm
Redbacked cutworm is a key pest of mint east of the Cascades. As mint begins to send up aerial growth in the spring, larvae feed underground by day, clipping off new spring shoots at or below ground level. At night, larvae feed above the soil surface. In some years, damage to mint during May and early June in central Oregon has been severe enough to result in extensive stand loss. It can be a worse problem in sandier, noncompacted soils.
Black vine weevil (Otiorhynchus sulcatus)
Strawberry root weevil (O. ovatus)
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-root-weevil
Root weevil larvae are legless white grubs with tan heads. They overwinter from two to eight inches deep in the soil. Adults are generally black, but may be brown or chocolate brown. Larvae feed on mint roots, and adults feed on foliage.
European black slug (Arion ater)
Gray garden slug (Deroceras reticulatum)
Great gray garden slug (Limax maximus)
Marsh slug (Deroceras laeve)
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-slug
Slugs are an occasional mint pest, mainly a problem in the Willamette Valley region of Oregon. Slug damage can be distinguished from that of cutworms and other pests by the presence of slime trails and their small sausage-shaped feces on the damaged plants as well as on the soil surface around damaged plants. Underground feeding on roots and tubers is characterized by shallow (0.12 inch) to deep (0.5 inch), smooth-sided pits that are usually less than 0.5 inch in diameter. Leaf damage is typified by removal of plant tissue between veins.
The most economically damaging species in Oregon is the “gray field slug” or gray garden slug (Deroceras reticulatum).
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-spider-mite
Spider mite adults are small, eight-legged, spiderlike animals associated with webbing and round eggs on the underside of leaves. They are pale green, yellowish to reddish, with two large, dark spots on each side of their bodies. They suck plant juices, causing leaves to yellow, dry, and fall under heavy infestations. They reduce oil yield and likely have negative impacts to quality. Predator mite populations can help maintain low infestation levels until populations grow too high based on conditions favorable to spider mites. Frequent field monitoring is critical.
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-thrips
Thrips are a sporadic pest in mint. They are small yellowish insects less than 1 mm long. Feeding on undersides of leaves injures cells. Damage appears as stippling, silvering and or yellowing of leaves. Generally, thrips are a localized problem in drought-stressed areas of fields or portions of fields adjacent to a crop just harvested. They are seldom a problem requiring treatment.
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-wireworm
Wireworms are brown, jointed, wiry, yellow to brown larvae of click beetles that feed on roots and underground stems of mint plants. Wireworms are a problem mainly when mint is planted into soil that is already infested. They do not become a problem in well managed and well-watered, established mint.
For more information, see: https://pnwhandbooks.org/plantdisease/host-disease/peppermint-mentha-spp-black-stem-rot
Black stem rot is caused by a fungus, Phoma strasseri, which is most active during cool, wet weather. Dark-brown or black cankers form on stems, usually at the junction of lateral branches. Cankers may girdle the stem, causing plant parts above the infection to wilt and die.
For more information, see: https://pnwhandbooks.org/plantdisease/host-disease/peppermint-mentha-spp-leaf-blight
Leaf blight is caused by a fungus, Cephalosporium sp. It infects leaves through wounds such as those from rust pustules, insects, or machinery.
Irregularly shaped black spots rapidly coalesce and eventually kill leaves. Infection can move down the leaf petiole into the stem. Infection develops rapidly in cool, wet weather and causes severe leaf drop, especially if hot, dry weather follows cool, wet weather.
For more information, see: https://pnwhandbooks.org/plantdisease/host-disease/peppermint-mentha-spp-nematode-needle
Longidorus elongatus is one of several nematodes that live in soil and cause plant decline by affecting the root system. Needle nematodes are frequently found in the Willamette Valley of Oregon, though seldom in high numbers. Needle nematodes are migratory ectoparasites found only in soil.
Above ground symptoms are similar to those of root-lesion nematode infections, but roots do not show lesions. The field may have open patches of severely depressed, red-green plants with short, weak root systems. On or near the roots it may be possible to see the nematodes, which look like slender, coiled threads about 0.25-inch-long and as thick as a spider web.
For more information, see: http://uspest.org/mint/pinnemaid.htm
Pin nematodes (Paratylenchus spp.) are the smalles plant parastic nematodes that attack plants. Adult females found in mint average 0.4 mm (0.016 inch). Pin nematodes are migratory ectoparasites. Pin nematodes easily detect and move towards plant roots, with the majority found around the root within 30 minutes of hatching.
For more information, see: https://pnwhandbooks.org/plantdisease/host-disease/peppermint-mentha-spp-nematode-root-knot
Root-knot nematodes live in soil and cause plant decline by affecting the root system. Galls form on roots; however, infection does not appear to cause yield loss under field conditions.
For more information, see: https://pnwhandbooks.org/plantdisease/host-disease/peppermint-mentha-spp-nematode-root-lesion
As with root-knot nematodes, root-lesion nematodes live in soil and cause plant decline by affecting the root system. Root-lesion nematodes are migratory endoparasites; part of the population is in soil and part in the roots most of the time. In peppermint, populations are relatively low through winter, peak in May, decline through late spring and early summer, then increase rapidly as summer progresses. Populations are highest generally just after harvest, then decline rapidly.
This nematode is the most frequent cause of open patches in a field with severely depressed, red-green plants with short, weak root systems. Roots and rhizomes have small reddish-brown lesions, which may blend together if the infestation is heavy.
This nematode’s most important role is in increasing the incidence and severity of Verticillium wilt on both peppermint and Scotch spearmint. It also can reduce winter hardiness on both mint types.
For more information, see: https://pnwhandbooks.org/plantdisease/host-disease/peppermint-mentha-spp-powdery-mildew
Powdery mildew is caused by a fungus, Golovinomyces biocellatus (syn = Erysiphebiocellata, formerly Erysiphe cichoracearum; anamorph Oidium erysiphoides), which overwinters on mint, mint stubble, and many wild hosts. A gray, powdery fungus grows on leaves, then leaves yellow and drop.
It is seldom serious enough on peppermint to warrant control measures, and does not impact native spearmint; however, it is very destructive on Scotch spearmint (grown in Washington) and has caused problems in Idaho peppermint. Interactions with some herbicides increase susceptibility to this disease.
For more information, see: https://pnwhandbooks.org/plantdisease/host-disease/peppermint-spearmint-mentha-spp-rust
Rust is caused by a fungus, Puccinia menthae, which overwinters on mint stubble and on wild and escaped mint. Eleven races have been identified in the Pacific Northwest. Peppermint rust is found frequently in western but not in central Oregon, while rust is a major disease on Scotch spearmint in central Oregon. Rust is found on native spearmint and Scotch spearmint in south-central Washington; however, it is not observed on peppermint due to high summer temperatures. It usually doesn’t reach economic treatment thresholds.
Rust causes brown, circular pustules on the leaves’ undersides followed by leaf yellowing and defoliation. A yellow spore stage (urediniospores) leads to reddish blisters on young shoots in spring, and a black spore stage (teliospores) occurs on stems and regrowth in fall. Swollen shoots with elongated, chlorotic internodes are associated with systemic infection.
For more information, see: https://pnwhandbooks.org/plantdisease/host-disease/peppermint-mentha-spp-spotted-wilt
The Impatiens necrotic spot virus (INSV) and the Tomato spotted wilt virus (TSWV) infect many economically important plants, including both dicots and monocots, and have been found in mint. A number of weedy hosts have been identified and include Lamb’s-quarters (Chenopodium album), Chickweed (Stellaria media), Shepherd’s purse (Capsella bursa-pastoris), and Purslane (Portulaca oleraceae). TSWV and INSV are transmitted by at least five species of thrips. The onion thrips and the flower thrips are known to be in the Pacific Northwest. The INSV is associated with the most severe symptoms in mint. New mint plantings show the worst symptoms, but they fade or disappear in later years.
Symptoms appear first on terminals and move progressively toward the plant base. Yellow leaf areas soon become necrotic, eventually killing leaves, followed by death of the entire aboveground portion of the plant. Early disease stages may be mistaken for powdery mildew. In the field, the underground portion of the plant regrows in the fall. Losses caused by this virus are unknown.
For more information, see: https://pnwhandbooks.org/plantdisease/host-disease/peppermint-mentha-spp-stolon-decay-canker
Stolon decay and canker is caused by several fungi that live in soil. Stolon decay is associated with Fusarium solani. Stem and stolon canker are caused by Rhizoctonia solani. Roots, runners, and rhizomes will have brown or black, progressively-rotting areas. Stands may be greatly reduced.
For more information, see: https://pnwhandbooks.org/plantdisease/host-disease/peppermint-mentha-spp-verticillium-wilt
Verticillium wilt is a critical disease, and the main driver of mint disease management. It is caused by a fungus, Verticillium dahliae, which lives in the soil and in diseased plants. Once established in soil it is almost impossible to eradicate because of the presence of microsclerotia, which germinate and infect roots. The fungus grows throughout the vascular system and up into mint stems. After diseased plant parts die, microsclerotia form and can survive in the soil for several years. The pathogen is spread with infected rhizomes used for planting, and in contaminated surface irrigation water. Co-infection of V. dahlia and the root lesion nematode, Pratylenchus penetrans, increases disease incidence and severity.
The VCG 2B strain of V. dahliae is most aggressive and prevalent in mint. This strain infects potato but symptoms and damage on potato are very mild or do not occur. The VCG 4A and VCG 4B strains, which are frequently obtained from potato, infect mint but symptoms and damage on mint are mild or not evident.
Native spearmint is relatively resistant, but Scotch spearmint and Black Mitcham peppermint are susceptible. Redefined Murray Mitcham is moderately resistant, but this cultivar is not as vigorous as Black Mitcham in the Columbia Basin. Grasses including corn and related crops do not sustain the population, but fallow or grass rotations alone may take many years to effectively reduce soil populations below economic levels.
Infection causes upper leaves to twist and curl, bunching at the top of the plant. Infected plants are stunted, and foliage turns yellowish to red or bronze. Lower leaves die first, then the whole above-ground part of the plant. With flowering or other stresses, stems or plants may die too rapidly for these symptoms to be readily observed while they are occurring.
One major limiting factor to a profitable mint crop is the development of dense weed populations, especially those weeds that affect the quality of the mint oil. Weeds have a significant impact on the organoleptic (i.e. flavor profile) quality of mint oil, ultimately reducing the value and marketability of the oil.
Newly established mint grows slowly and is susceptible to weed competition. Competition is most severe in mint during the first and second year of the stand before the canopy closes over. Even after canopy closure, winter annual and perennial weeds can be major problems. It is important to reduce weed populations before the crop is planted because the herbicide options for newly established mint are limited.
Oil quality problems are more serious with broadleaf weeds than with grasses. Oil quality problems are most severe when pigweed, common groundsel, mayweed chamomile, prickly lettuce, and salsify are present. In addition to contaminating the oil, weeds also reduce the yield of mint crops. Weeds can also become a source of disease and insect pests if not managed effectively.
With the use of rotation crops, weeds must be eliminated before they go to seed to prevent the buildup of weed seed in the soil. Planting an annual crop such as grain or sudangrass for two seasons preceding the establishment of a mint field is a good strategy, because herbicides registered for use in these crops effectively control the broadleaf weeds that are most troublesome in mint.
Seedbed preparation activities before planting will eliminate many annual weeds, as will an application of herbicide before planting. Perennial weeds can be controlled by crop rotation, by fallowing in conjunction with repeated cultivations, or by herbicide applications.
The primary method of weed management after the mint crop is established is the use of herbicides. Because of the narrow planting arrangement of this crop, and the rapid spread of plants by stolons, close cultivation is generally not practiced after the first year.
Hand weeding, though costly, is also frequently necessary before harvest to eliminate mature broadleaf weeds such as mayweed chamomile, pigweed, or prickly lettuce that have escaped herbicide treatments, in order to prevent oil contaminants.
Preplant through planting
Mint can be planted in both spring and fall in the Pacific Northwest. Exact planting time varies based on region, soil moisture and temperature. Spring planting can take place anywhere between late February and April. Fall planting often takes place after the third week of September, through October. In Washington, mint is most commonly planted in the spring. In Idaho and western and northeastern Oregon, planting takes place primarily in the fall. Fall planted crops can be more challenging, depending on water availability and weather. Use of certified mint rootstock reduces the risk of introducing diseases, weeds or insects that may be associated with contaminated planting material.
Mint is planted in rows and can be harvested the first season, but at a lower yield than in subsequent years. By the second growing season, the plants are allowed to spread out to create a solid mat. However, in areas where furrow irrigation is used, rows and furrows must be maintained annually. A typical mint stand will stay in production for about three to five years.
Mint is often rotated with other crops, with the field returning to mint after three or more years. Rotation aids in the control of nematodes, diseases and weeds prior to planting. Longer rotations between mint stands is a strategy often used to mitigate against disease inoculum buildup in the soil of fields where problems have existed previously. After the rotational crop is removed, the ground is prepared for planting by plowing and disking, which also removes annual weeds that may be present. Irrigation method (furrow vs. sprinkler) will impact subsequent pest management practices. Irrigation can also impact pesticide efficacy.
Planting is a critical time for evaluation of field history and soil to understand Verticillium wilt pressure. Current soil testing methods only provide a coarse estimate of Verticillium wilt pressure because commercial tests cannot distinguish between, or specifically identify, the strains that infect mint.
Soil fumigation takes place during this crop stage, but does not take place once the crop is planted. In the Willamette Valley, fumigation is not as common, while in northeastern Oregon, 20% tpo40% of acres are estimated to be fumigated. In Washington, approximately 40% to 50% of acres are fumigated.
|
PAMS1 practice |
Pre-plant through planting pest management activities |
Target pest(s) |
|
Prevention |
Ensure healthy rootstock, including certified stock |
Verticillium wilt, nematodes |
|
Avoidance |
Use rotation crops – wheat, alfalfa, annual cereals |
Nematodes and soil borne diseases, broadleaf weeds; limits access to primary and alternative crop hosts |
|
Follow potatoes or onions to take advantage of soil fumigation used for these crops |
Nematodes, symphylans, Verticillium wilt |
|
|
Field selection based on disease history |
Verticillium wilt |
|
|
Monitoring |
Soil testing; pre-plant nematode testing |
Verticillium wilt, nematodes |
|
Suppression |
Soil-applied insecticides/fumigants:
Note: sandy soils do not fumigate well; poor efficacy is achieved in some areas |
|
|
Biological nematicides (used by some growers):
|
Nematodes |
|
|
Herbicides:
Glyphosate (Roundup): used in the fall after previous years’ crop Terbacil (Sinbar): used just after planting Sulfentrazone (Spartan) (post-planting) |
Perennial weeds |
|
|
Biofumigants including mustards: used in both conventional and organic fields |
Perennial weeds, nematodes, Verticillium wilt |
1 See Appendix “Using PAMS Terminology”
In Washington, there is not much dormancy after planting due to the spring planting time. In the Willamette Valley, northeastern Oregon, Columbia Basin, and Idaho, mint is planted in the fall and winter, from October/November through February/March, so has a dormant period before growth begins.
The planting year (first year) dormancy period differs from the established crop dormancy in that the lack of growth and spread between rows from rhizomes leaves more bare soil in the first year. Typically, fall-planted mint is assumed to be dormant at the time of planting, and does not actively grow (above ground) until the following spring. Rhizomes are planted into the fields, but there is no visible vegetation at this time. Dormancy occurs until there is visible growth above the soil surface.
Harrowing beds
Cultivation (at emergence)
Reservoir tillage (trade name is “Dammer Diking): forming or cleaning of furrows or rills for surface irrigation.
Flaming for weeds
|
PAMS practice |
First year dormancy pest management activities |
Target pest(s) |
|
Prevention |
||
|
Avoidance |
||
|
Monitoring |
Scouting |
Cutworm |
|
Suppression |
Herbicide applications: First (establishment) year, dormant (pre-emergence):
(Note: some herbicide products cannot be used during establishment year dormancy but can be used during dormancy after establishment) |
Burn down for soil residual weeds |
|
Removal of winter annual weeds (hand-hoeing if necessary) |
Weed management |
|
|
In the Willamette Valley, growers use:
|
||
|
Flaming |
Weeds |
None at this time
None at this time
None at this time
Established year dormancy takes place between October and March, when plants have gone dormant and are no longer actively growing. This takes place every year of the established crop, which may remain in production for up to five to six years.
|
PAMS practice |
Established crop dormancy pest management activities |
Target pest(s) |
|
Prevention |
||
|
Avoidance |
Ensure good weed control |
Winter annuals; perennial weeds; growers also attribute good weed control as helping with cutworm management |
|
Mow regrowth from the previous year, which can provide new shoots and encourage cutworm feeding |
Cutworms |
|
|
Monitoring |
Scouting |
Cutworm, weeds |
|
Suppression |
Flaming weeds |
Winter annuals |
|
Insecticide application: Chlorpyrifos (Lorsban) |
Cutworm |
|
|
Established crop, dormant (pre-emergence) herbicide applications:
Note: different mixes and higher concentrations are used during established year dormancy based on establishment of perennial weeds |
Burn down herbicides for established and newly germinated weeds; pre-emergent herbicides for fall/winter germinating weeds |
|
|
In the Willamette Valley, growers use:
|
Vegetative growth takes place at different timings depending on the planting time, region and program. For double-cut mint, vegetative growth spans from March or April to early June or mid-July, when the first cutting would take place, then again (following a short postharvest phase of 2–3 weeks) after the first cutting. Second cutting usually occurs in September.
For single-cut mint, vegetative growth generally begins at the same time as double-cut mint, in March or April depending on the spring, with rapid linear growth in May and June until harvest, which is generally in late July or early August.
Note: see https://catalog.extension.oregonstate.edu/em9018 for biomass curves for WV single-cut mint.
During this period of active vegetative growth, many insects, mites, diseases and weeds need to be controlled. At this time, fields are scouted for pests, irrigation continues, fertilizers are applied and pest control measures are implemented as needed. Hand-hoeing is sometimes needed in fields where weeds have escaped other control measures.
Spearmint is harvested when the plants are in full bloom, while peppermint is harvested at 10% bloom. Delayed harvest past optimum maturity will cause a rapid deterioration of mint oil quality and yield. The mint hay is allowed to partially dry after the mint is cut and windrowed. It is then chopped and blown into tubs and hauled to the on-farm mint distillery. The mint field continues to be irrigated and fertilized between cuts to encourage vigorous regrowth.
|
PAMS practice |
Vegetative growth pest management activities |
Target pest(s) |
|
Prevention |
No effective tactics available |
|
|
Avoidance |
Preserve natural predators (big-eyed bugs [Geocoris spp.], damsel bugs, spiders, lacewing, lady beetles, and predatory mites) |
Mites |
|
Monitoring |
Scouting |
Weeds (grasses), mites, root weevil, cutworms, other insects |
|
Utilization of OSU mint pest alerts |
Mint Root Borer, Variegated Cutworms, Alfalfa/Cabbage Loopers |
|
|
Petiole sampling/testing |
||
|
Suppression |
Hand rogueing |
Weeds |
|
Ladybeetle release |
Aphids |
|
|
Release of predator mites |
Spider mites |
|
|
Insecticide applications:
|
Nematodes, symphylans, cutworms |
|
|
Caterpillars, worms |
|
|
Root weevil |
|
|
Cutworm, mint root borer |
|
|
Miticide applications:
|
mites |
|
|
Fungicide/biofungicide applications:
|
Mildew |
|
Note: in the Willamette Valley, rust requires preventative control every 2–3 weeks until harvest |
Preventative sprays for mildew, rust |
|
|
Herbicide applications:
|
Emerged annual and perennial weeds |
|
|
Biological Nematicide applications:
|
This section applies to the post-harvest period following single-cut mint, as well as the postharvest period following the second cutting of double-cut mint. The following section, “Between cuttings,” addresses post-harvest issues following the first cutting of double-cut mint.
The timeframe for this stage ranges from early to mid-August through October, and into winter dormancy.
|
PAMS practice |
Post-harvest pest management activities |
Target pest(s) |
|
Prevention |
||
|
Avoidance |
Add mint crop residue back to fields to increase soil nutrients and maintain healthy plants |
Healthy plants better avoid pest outbreaks |
|
Monitoring |
Visual scouting |
Weeds, cutworms, armyworms |
|
Soil/rhizome sampling |
Mint root borer, cutworms |
|
|
Testing for nematodes after harvest, while soil temperatures are still warm |
Nematodes |
|
|
Suppression |
Hand weeding/hoeing |
General weed control |
|
Flaming |
Weeds |
|
|
Insecticide applications: |
||
|
Root borer, spring cutworms |
|
|
Root borer |
|
|
Late season armyworm |
|
|
Nematicides:
|
Nematodes, root borer, symphylans |
|
|
Nematodes |
|
|
Herbicide applications: |
||
|
General weed control |
|
|
Bromoxynil (Buctril) |
Groundsel |
This stage takes place in double-cut mint, and comprises the period after the first cutting and before the second cutting. The timeframe for this stage ranges from mid-June to mid-July (timing of first cutting) through mid-August. Commonly, there are 14–21 days of “post-harvest” between the first and second cuttings, and before vegetative growth begins. This stage covers that “post-harvest” stage after the first cutting, and before vegetative growth begins.
When the canopy is opened up by the first cutting, weeds can quickly become a problem. So good weed control is a primary activity during this stage.
|
PAMS practice |
Between cuttings pest management activities |
Target pest(s) |
|
Prevention |
||
|
Avoidance |
||
|
Monitoring |
Scouting |
Weeds |
|
Suppression |
Herbicide applications:
|
General weed control |
For more information, see: https://pnwhandbooks.org/insect/agronomic/mint/mint-mint-stem-borer.
Mint stem borer is currently not a threshold pest, but the problem can intensify when Verticillium wilt is also an issue. This pest should be monitored as there are currently no registered insecticides for control.
Emerging weed issues that need monitoring include bladder campion (Silene vulgaris), night flowering catch fly (Silene noctiflora), and sulfur cinquefoil (Potentilla supina).
Also, Terbacil resistant pigweeds are an established problem, including redroot pigweed, prostrate pigweed, and palmer amaranth.
Ongoing monitoring for emerging weeds
Jepson, P.C., Murray, K., Bach, O., Bonilla, M.A., Neumeister, L. (2020). Selection of pesticides to reduce human and environmental health risks: a global guideline and minimum pesticides list. Lancet Planetary Health 4: e56-53. Available on-line at: https://doi.org/10.1016/S2542-5196(19)30266-9
Pacific Northwest Weed Management Handbook. 2018. Oregon State University, Washington State University, and the University of Idaho. https://pnwhandbooks.org/weed
Pacific Northwest Plant Disease Management Handbook. 2018. Oregon State University, Washington State University, and the University of Idaho. https://pnwhandbooks.org/plantdisease
Pacific Northwest Insect Management Handbook. 2018. Oregon State University, Washington State University, and the University of Idaho. https://pnwhandbooks.org/insect
Pest Management Strategic Plan for Pacific Northwest Mint Production. 2002. https://ipmdata.ipmcenters.org/documents/pmsps/PNWMintPMSP.pdf
UC IPM Pest Management Guidelines: http://ipm.ucanr.edu/PMG/r61700111.html
Appendix A
|
Field activities (other than pest management) |
||||||||||||
|
Activity |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Soil preparation |
x |
x |
x |
x |
x |
|||||||
|
Soil analysis |
x |
x |
x |
x |
x |
|||||||
|
Planting |
x |
x |
x |
x |
||||||||
|
Fertilization |
x |
x |
x |
x |
||||||||
|
Irrigation |
x |
x |
x |
x |
x |
x |
||||||
|
Harvest |
x |
x |
x |
|||||||||
|
Pest management activities |
||||||||||||
|
Activity |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Fungicide application |
x |
|||||||||||
|
Fumigation preplant |
x |
x |
x |
x |
x |
|||||||
|
Scouting |
x |
x |
x |
x |
x |
x |
x |
x |
x |
x |
||
|
Herbicide, dormancy |
x |
x |
x |
x |
x |
|||||||
|
Hand rogueing weeds |
x |
x |
x |
|||||||||
|
Herbicide, postemergent |
x |
x |
x |
x |
x |
|||||||
|
Herbicide, postharvest |
x |
x |
x |
|||||||||
|
Insecticide application |
x |
x |
x |
x |
x |
x |
x |
x |
||||
|
Miticide application |
x |
x |
x |
x |
||||||||
|
Nematicide application |
x |
x |
||||||||||
Notes: X = times when pest-management strategies are applied to control these pests, not all times when pest is present.
|
Insects |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Alfalfa looper |
X |
X |
||||||||||
|
Aphid |
X |
X |
||||||||||
|
Armyworm |
X |
X |
X |
|||||||||
|
Cabbage looper |
X |
X |
||||||||||
|
Cutworm |
X |
X |
X |
|||||||||
|
Grasshopper |
X |
|||||||||||
|
Mint root borer |
X |
X |
X |
|||||||||
|
Mint stem borer |
X |
X |
||||||||||
|
Root weevil |
X |
|||||||||||
|
Spider mite |
X |
X |
X |
X |
||||||||
|
Pathogens |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Nematodes (needle, pin, Root-knot, Root-lesion) |
X |
X |
X |
X |
||||||||
|
Powdery mildew |
X |
|||||||||||
|
Verticillium wilt |
X |
X |
X |
X |
X |
|||||||
|
Weeds |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Annual grasses |
X |
X |
X |
X |
X |
X |
X |
|||||
|
Perennial grasses |
X |
X |
||||||||||
|
Annual broadleaves |
X |
X |
X |
X |
X |
X |
X |
|||||
|
Perennial broadleaves |
X |
X |
|
Field activities (other than pest management) |
||||||||||||
|
Activity |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Cultivation (first year) |
X |
X |
||||||||||
|
Fertilization |
X |
X |
X |
X |
X |
X |
||||||
|
Irrigation |
X |
X |
X |
X |
X |
X |
||||||
|
Soil analysis |
X |
X |
X |
X |
||||||||
|
Soil preparation |
X |
X |
X |
X |
X |
|||||||
|
Planting |
X |
X |
X |
X |
X |
|||||||
|
Plant tissue analysis |
X |
X |
X |
|||||||||
|
Corrugate (rill) |
X |
X |
X |
X |
||||||||
|
Harvest |
X |
X |
X |
X |
||||||||
|
Pest management activities |
||||||||||||
|
Activity |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Fungicide application |
X |
X |
X |
|||||||||
|
Fumigation (preplant) |
X |
X |
X |
X |
X |
X |
||||||
|
Scouting/monitoring |
X |
X |
X |
X |
X |
X |
X |
X |
X |
X |
||
|
Herbicide, dormancy |
X |
X |
X |
|||||||||
|
Hand rogueing weeds |
X |
X |
||||||||||
|
Herbicide, post-emergence |
X |
X |
X |
X |
X |
|||||||
|
Herbicide, between cuttings |
X |
|||||||||||
|
Herbicide, post-harvest single cut |
X |
X |
X |
|||||||||
|
Insecticide |
X |
X |
X |
X |
X |
X |
||||||
|
Miticide |
X |
X |
X |
X |
||||||||
|
Nematicide |
X |
X |
X |
|||||||||
Appendix D
Notes: X = times when pest-management strategies are applied to control these pests, not all times when pest is present.
|
Insects |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Alfalfa/Cabbage looper |
X |
X |
||||||||||
|
Aphid |
X |
X |
||||||||||
|
Cutworm/Armyworm |
X |
X |
X |
X |
X |
X |
||||||
|
Grasshopper |
X |
X |
X |
X |
||||||||
|
Mint flea beetle |
X |
|||||||||||
|
Mint root borer |
X |
X |
X |
|||||||||
|
Mint stem borer |
X |
X |
X |
|||||||||
|
Strawberry root weevil |
X |
|||||||||||
|
Spider mite |
X |
X |
X |
X |
||||||||
|
Wireworm |
X |
X |
||||||||||
|
Pathogens |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Black stem rot |
X |
X |
||||||||||
|
Nematodes (needle, Root-knot, Root-lesion) |
X |
X |
X |
X |
||||||||
|
Powdery mildew |
X |
X |
X |
|||||||||
|
Verticillium wilt |
X |
X |
X |
|||||||||
|
Rust |
X |
|||||||||||
|
Weeds |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Annual grasses |
X |
X |
X |
X |
X |
|||||||
|
Perennial grasses |
X |
X |
X |
X |
||||||||
|
Annual broadleaves |
X |
X |
X |
X |
X |
X |
X |
X |
||||
|
Perennial broadleaves |
X |
X |
X |
Appendix E
|
Field activities (other than pest management) |
||||||||||||
|
Activity |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Soil sampling |
X |
X |
X |
X |
||||||||
|
Soil Prep/tillage |
X |
X |
X |
|||||||||
|
Planting |
X |
X |
X |
X |
||||||||
|
Irrigation |
X |
X |
X |
X |
X |
X |
X |
X |
||||
|
Fertilization |
X |
X |
X |
|||||||||
|
Hoeing |
X |
X |
X |
X |
||||||||
|
Petiole sampling |
X |
X |
X |
X |
||||||||
|
Irrigation monitoring |
X |
X |
X |
X |
X |
X |
||||||
|
Harvest |
X |
X |
X |
X |
X |
|||||||
|
Pest management activities |
||||||||||||
|
Activity |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Pest scouting |
X |
X |
X |
X |
X |
X |
X |
X |
||||
|
Nematode sampling |
X |
X |
X |
X |
||||||||
|
Miticide application |
X |
X |
X |
X |
||||||||
|
Nematicide application |
X |
X |
X |
X |
||||||||
|
Insecticide application |
X |
X |
X |
X |
X |
|||||||
|
Fungicide application |
X |
X |
X |
X |
X |
|||||||
|
Fumigation |
X |
X |
X |
|||||||||
|
Herbicide, pre-emergent |
X |
X |
X |
X |
||||||||
|
Herbicide, vegetative growth |
X |
X |
X |
X |
||||||||
Appendix F
Notes: X = times when pest-management strategies are applied to control these pests, not all times when pest is present.
|
Insects |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Aphid |
x |
x |
x |
|||||||||
|
Armyworm |
X |
|||||||||||
|
Cutworm |
X |
X |
||||||||||
|
Grasshopper |
X |
X |
X |
|||||||||
|
Mint root borer |
X |
X |
||||||||||
|
Spider mite |
X |
X |
X |
X |
X |
|||||||
|
Pathogens |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Black stem rot/phoma |
X |
X |
X |
X |
X |
X |
||||||
|
Nematodes (needle, pin, Root-knot, Root-lesion) |
X |
X |
X |
X |
||||||||
|
Powdery mildew |
X |
X |
X |
X |
X |
|||||||
|
Rust |
X |
X |
X |
|||||||||
|
Rhizoctonia |
X |
X |
||||||||||
|
Fusarium |
X |
X |
||||||||||
|
Weeds |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Annual grasses |
X |
X |
X |
X |
X |
X |
||||||
|
Perennial grasses |
X |
X |
X |
X |
X |
X |
||||||
|
Annual broadleaves |
X |
X |
X |
X |
X |
X |
||||||
|
Perennial broadleaves |
X |
X |
X |
X |
X |
X |
X |
X |
X |
Appendix G
|
Field activities (other than pest management) |
||||||||||||
|
Activity |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Fertilization/lime application |
X |
X |
X |
X |
||||||||
|
Irrigation |
X |
X |
X |
X |
X |
X |
||||||
|
Planting |
X |
X |
X |
|||||||||
|
Soil sampling (nutrients) |
X |
X |
||||||||||
|
Soil sampling (pests) |
X |
X |
X |
X |
X |
X |
||||||
|
Harvest |
X |
|||||||||||
|
Rolling mint |
X |
|||||||||||
|
Pest management activities |
||||||||||||
|
Activity |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Herbicide application |
X |
X |
X |
X |
X |
|||||||
|
Insecticide application |
X |
X |
X |
X |
X |
X |
X |
|||||
|
Pest scouting |
X |
X |
X |
X |
X |
X |
X |
X |
||||
|
Nematode sampling |
X |
X |
X |
X |
||||||||
|
Miticide application |
X |
X |
X |
X |
||||||||
|
Nematicide application |
X |
X |
||||||||||
|
Fungicide application |
X |
X |
X |
X |
X |
|||||||
Appendix H
Notes: X = times when pest-management strategies are applied to control these pests, not all times when pest is present.
|
Insects |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Alfalfa looper |
X |
|||||||||||
|
Aphid |
X |
X |
X |
X |
X |
|||||||
|
Cabbage looper |
X |
|||||||||||
|
Cutworm |
X |
X |
||||||||||
|
Garden symphylan |
X |
X |
||||||||||
|
Mint root borer |
X |
|||||||||||
|
Root weevil |
X |
|||||||||||
|
Spider mite |
X |
X |
X |
|||||||||
|
Pathogens |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Nematodes (needle, pin, Root-knot, Root-lesion) |
X |
X |
||||||||||
|
Rust |
X |
X |
X |
X |
||||||||
|
Weeds |
Jan |
Feb |
Mar |
Apr |
May |
June |
July |
Aug |
Sept |
Oct |
Nov |
Dec |
|
Annual grasses |
X |
X |
X |
X |
||||||||
|
Perennial grasses |
X |
X |
X |
X |
||||||||
|
Annual broadleaves |
X |
X |
X |
X |
||||||||
|
Perennial broadleaves |
X |
X |
X |
X |
Appendix I
The letters below represent four categories of nontarget risk potentially affected by pesticide use. If a letter is used, it indicates that mitigation is needed at commonly used application rates in order to reduce risk. Risks were calculated using the risk assessment tool IPM PRiME. This table does not substitute for any mitigations required by the product label. For more information see Appendix X “Pesticide Risk Classification”.
A= Risks to aquatics: invertebrates and fish
T= Risks to terrestrial wildlife: birds and mammals
P= Risks to pollinators: risk of hive loss
B= Risks to bystanders: e.g., a child standing at the edge of the field
“ND” means no data is available for this product.
“–“ means that risks are not anticipated for this product based on the categories of risk analyzed
HHP = Any product highlighted in yellow is classified as a “highly hazardous pesticide” (HHP) by the World Health Organization and the Food and Agriculture Organization of the United Nations. These products may pose significant risks to human health or the environment, and risk reduction measures may not be effective in mitigating these risks.
|
Risks requiring mitigation |
Pre-plant |
Vegetative Growth |
Between cuttings |
Dormancy |
Target pests |
Comments |
|
|
Pesticides |
Average number of applications per crop stage, if used |
||||||
|
Insecticides and fumigants |
|||||||
|
1,3 dichloropropene (Telone II, Telone C-17) |
A, T, P, B |
1 |
Nematodes |
||||
|
Abamectin (ABBA, Agri-Mek) |
A, P |
1 |
Mites |
||||
|
Acephate (Orthene) |
T, P |
1 |
Caterpillars |
||||
|
Beauveria bassiana (Mycotrol ES) |
_ |
Not widely used |
|||||
|
Bifenazate (Acramite 4SC) |
_ |
1 |
Mites |
||||
|
Bt (Bacillus thuringiensis) |
_ |
3 |
Caterpillars |
Mostly organic |
|||
|
Burkholderia spp. (Venerate XC) |
ND |
Mites, caterpillars |
Not widely used |
||||
|
Chlorantraniliprole (Coragen) |
- |
1 |
Mint root borer |
* Used either preharvest in July or postharvest in Sept/Oct |
|||
|
Chlorantraniliprole/thiamethoxam (Voliam Flexi) |
A, P |
NU |
|||||
|
Chlorpyrifos (Lorsban Advanced) |
A, T, P, B |
1 |
1 |
Mint root borer |
In fall/after harvest. Used for cutworm in early spring |
||
|
Dicofol (Dicofol 4E) |
T, B |
Not widely used |
|||||
|
Ethoprop (Mocap EC or 15G) |
HHP |
1 |
Nematodes, mint root borer, symphylan |
||||
|
Etoxazole (Zeal) |
A |
1 |
Mites |
||||
|
Fenpyroximate (FujiMite 5EC ) |
A, T |
1 |
Mites |
||||
|
Flonicamid (Beleaf 50SG) |
- |
Not widely used |
|||||
|
Grandevo (Chromobacterium subtsugae ) |
ND |
Not widely used |
|||||
|
GS-omega/kappa/Bacillus thuringiensis (Spear-C Biological Insecticide) |
ND |
Not widely used |
|||||
|
Hexythiazox (Onager Optek) |
- |
1 |
Mites |
||||
|
Indoxacarb (Avaunt) |
P |
Not widely used |
|||||
|
Iron phosphate + spinosad (Bug-N-Sluggo) |
P |
1 |
Snails, slugs |
Willamette Valley only |
|||
|
Malathion (Gowan Malathion 8) |
P |
1 |
|||||
|
Metaldehyde |
- |
1 |
Willamette Valley only |
||||
|
Metam potassium |
A, T |
1 |
|||||
|
Metam sodium (Vapam) |
A, T |
1 |
After harvest |
||||
|
Methomyl (Lannate SP) |
HHP |
Not widely used |
|||||
|
Methoxyfenozide (Intrepid 2F) |
- |
Not widely used |
|||||
|
Neem oil or azadirachtin (Neemix 4.5 IGR, Certis) |
- |
Not widely used |
|||||
|
Oxamyl (Vydate L) |
HHP |
1 |
1 |
Nematodes |
|||
|
Oxydemeton-methyl (MSR Spray Concentrate) |
HHP |
Not widely used |
|||||
|
Parasitic nematodes (BioNem-C, Becker Underwood) |
ND |
Not widely used |
|||||
|
Propargite (Omite 6E, Comite) |
T |
1 |
Mites |
||||
|
Pyrethrins |
P |
Not widely used |
|||||
|
Spinetoram (Radiant SC) |
P |
Not widely used |
|||||
|
Spinosad (Success, Entrust SC) |
P |
Not widely used |
|||||
|
Tebufenozide (Confirm 2F) |
- |
1 |
caterpillars |
||||
|
Thiamethoxam (Actara) |
A, P |
2 |
Not widely used; expensive |
||||
|
Fungicides |
|||||||
|
Azoxystrobin (Quadris Flowable) |
A |
3 |
Mildew |
||||
|
Azoxystrobin + propiconazole (Quilt, Quilt Xcel) |
A |
3 |
Mildew |
||||
|
Bacillus amyloliquefaciens strain D747 (Double Nickel LC) |
ND |
Mildew |
Efficacy unknown; not widely used |
||||
|
Bacillus subtilis (Serenade MAX) |
- |
Mildew |
|||||
|
Chlorothalonil (Equis) |
A, T |
0 |
OR label; not registered in WA or ID |
||||
|
JMS Stylet Oil |
ND |
||||||
|
Myclobutanil (Rally 40WSP) |
T |
Mildew |
|||||
|
Potassium bicarbonate (Kaligreen) |
- |
Mildew |
|||||
|
Propiconazole (Tilt, Bumper, Propimax EC) |
- |
3 |
Mildew |
||||
|
Pyraclastrobin (Headline) |
A |
Mildew |
|||||
|
Reynoutria sachalinensis (Regalia) |
- |
||||||
|
Sulfur products |
- |
Mildew |
|||||
|
Herbicides |
|||||||
|
Bentazon (Basagran) |
- |
1 |
Usually establishment year only |
||||
|
Bromoxynil (Buctril) |
- |
1 |
1 |
1 |
Usually establishment year only |
||
|
Carfentrazone (Aim) |
- |
1 |
Willamette Valley only |
||||
|
Clethodim (Select Max) |
- |
1 |
Used when needed |
||||
|
Clomazone (Command) |
- |
1 |
Used mainly in WA |
||||
|
Clopyralid (Stinger) |
- |
Used when needed but not every year |
|||||
|
Diuron (Karmex/Direx) |
T |
1 |
Not used in WA |
||||
|
Flumioxazin (Chateau) |
HHP |
1 |
Not widely used in WA. Used in other areas almost every year. |
||||
|
MCPB (Thistrol) |
- |
1 |
Only used on bindweed patches, not entire fields |
||||
|
Napropramide (Devrinol) |
T |
||||||
|
Oxyfluorfen (Goal) |
A, T |
1 |
Used some in Willamette Valley, but not in other areas |
||||
|
Paraquat (Gramoxone Inteon, Firestorm) |
HHP |
1 |
Used almost every year in all areas |
||||
|
Pendimethalin (Prowl H20) |
T |
1 |
Used in WA and ID only |
||||
|
Pyridate (Tough) |
- |
1 |
Used when needed; between double cuts only pending EPA Section 3 application determination |
||||
|
Quizalafop (Assure II) |
- |
1 |
Used rarely but when needed |
||||
|
Sethoxydim (Poast) |
- |
1 |
Used rarely but when needed |
||||
|
Sulfentrazone (Spartan) |
T |
1 |
Not widely used (all regions) |
||||
|
Terbacil (Sinbar) |
- |
1+ |
1 |
1 |
1 |
||
|
Trifluralin (Treflan) |
T |
1 |
Not often used |
||||
Appendix J
Rating scale: E = excellent (90–100% control); G = good (80–90% control); F = fair (70–80% control); P = poor (< 70% control); ? = efficacy unknown in management system—more research needed.
|
Management tools |
Leaf Blight |
Black stem rot |
Needle nematode |
Root-rot nematode |
Root-lesion nematode |
Powdery Mildew |
Spotted wilt |
Stolon canker and decay |
Verticillium wilt |
Rust |
Comments |
|
Fungicides and fumigants |
|||||||||||
|
1,3 dichloropropene (Telone II, Telone C-17) |
F |
F |
F |
||||||||
|
Azoxystrobin (Quadris Flowable) |
G |
G |
|||||||||
|
Azoxystrobin + propiconazole (Quilt, Quilt Xcel) |
G |
G |
|||||||||
|
Bacillus amyloliquefaciens strain D747 (Double Nickel LC) |
Not widely used |
||||||||||
|
Bacillus subtilis (Serenade MAX) |
Not widely used |
||||||||||
|
Chlorothalonil (Equis) |
Not widely used |
||||||||||
|
JMS Stylet Oil |
Not widely used |
||||||||||
|
Metam sodium (Vapam HL) |
G |
G |
G |
G |
|||||||
|
Myclobutanil (Rally 40WSP) |
G |
G |
|||||||||
|
Potassium bicarbonate (Kaligreen) |
Not widely used |
||||||||||
|
Potassium N-methyldythiocarbamate (K-pam) |
Not widely used |
||||||||||
|
Propiconazole (Tilt, Bumper, Propimax EC) |
G |
G |
|||||||||
|
Pyraclastrobin (Headline) |
G |
G |
|||||||||
|
Reynoutria sachalinensis (Regalia) |
Not widely used |
||||||||||
|
Sulfur products |
G |
||||||||||
|
Unregistered/new chemistries |
|||||||||||
|
Fluopyram (Vellum) |
? |
? |
? |
Registration pending. Efficacy research underway. |
|||||||
Appendix K
Rating scale: E = excellent (90–100% control); G = good (80–90% control); F = fair (70–80% control); P = poor (< 70% control); ? = efficacy unknown, more research needed
|
Management tools |
Alfalfa Looper |
Aphid |
Armyworm |
Cranefly |
Cabbage looper |
Cutworm |
Garden symphylan |
Grasshopper |
Mint flea beetle |
Mint root borer |
Mint stem borer |
Painted lady |
Redback cutworm |
Root weevil |
Slug |
Spider mite |
Thrips |
Wireworm |
Comments |
|
Insecticides |
|||||||||||||||||||
|
Abamectin (ABBA, Agri-Mek 0.15EC) |
G |
||||||||||||||||||
|
Acephate (Orthene) |
G |
G |
G |
G |
G |
||||||||||||||
|
Beauveria bassiana (Mycotrol ES) |
Not widely used |
||||||||||||||||||
|
bifenazate (Acramite 4SC) |
G |
||||||||||||||||||
|
Bt (Bacillus thuringiensis) |
F |
F |
F |
F |
|||||||||||||||
|
Burkholderia spp. (Venerate XC) |
Not widely used |
||||||||||||||||||
|
Chlorantraniliprole (Coragen) |
G |
G |
G |
G |
G |
||||||||||||||
|
Chlorantraniliprole/thiamethoxam (Voliam Flexi) |
G |
G |
G |
G |
G |
G |
Expensive |
||||||||||||
|
Chlorpyrifos (Lorsban Advanced) |
G |
G |
G |
G |
G |
G |
G |
||||||||||||
|
Dicofol (Dicofol 4E) |
Not widely used |
||||||||||||||||||
|
Ethoprop (Mocap EC or 15G) |
F |
||||||||||||||||||
|
Etoxazole (Zeal) |
G |
||||||||||||||||||
|
Fenpyroximate (FujiMite 5EC ) |
G |
||||||||||||||||||
|
Flonicamid (Beleaf 50SG) |
G |
||||||||||||||||||
|
Grandevo (Chromobacterium subtsugae ) |
Not widely used |
||||||||||||||||||
|
GS-omega/kappa/Bacillus thuringiensis (Spear-C Biological Insecticide) |
Not widely used |
||||||||||||||||||
|
Hexythiazox (Onager Optek) |
G |
||||||||||||||||||
|
Indoxacarb (Avaunt) |
Not widely used |
||||||||||||||||||
|
Iron phosphate + spinosad (Bug-N-Sluggo) |
Not widely used |
||||||||||||||||||
|
Malathion (Gowan Malathion 8) |
G |
||||||||||||||||||
|
Metaldehyde |
Not widely used |
||||||||||||||||||
|
Metam sodium (Vapam) |
Not widely used |
||||||||||||||||||
|
Methomyl (Lannate SP) |
Not widely used |
||||||||||||||||||
|
Methoxyfenozide (Intrepid 2F) |
Not widely used |
||||||||||||||||||
|
Neem oil or azadirachtin (Neemix 4.5 IGR, Certis) |
Not widely used |
||||||||||||||||||
|
Oxamyl (Vydate L) |
Not widely used |
||||||||||||||||||
|
Oxydemeton-methyl (MSR Spray Concentrate) |
G |
||||||||||||||||||
|
Parasitic nematodes (BioNem-C, Becker Underwood) |
Not widely used |
||||||||||||||||||
|
Propargite (Omite 6E, Comite) |
G |
||||||||||||||||||
|
Pyrethrins |
Not widely used |
||||||||||||||||||
|
Spinetoram (Radiant SC) |
Not widely used |
||||||||||||||||||
|
Spinosad (Success, Entrust SC) |
Not widely used |
||||||||||||||||||
|
Tebufenozide (Confirm 2F) |
NOT WIDELY USED |
||||||||||||||||||
|
Unregistered/new chemistries |
|||||||||||||||||||
|
Lambda-cyhalotrhin (Warrior) |
E |
E |
Registration pending |
||||||||||||||||
|
Spiromesifen (Oberon) |
G |
Registration pending |
|||||||||||||||||
|
Cyantraniliprole (Verimark) |
? |
? |
Efficacy research being conducted |
||||||||||||||||
Appendix L
Rating scale: E = excellent (90–100% control); G = good (80–90% control); F = fair (70–80% control); P = poor (<70% control); ? = efficacy unknown—more research needed
Note: Weed size or stage of growth is an important consideration with most postemergence herbicides.
In “Type” column, Pre = soil-active against pre-emerged weeds; Post = foliar-active against emerged weeds.
|
Management tools |
Pre/ Post |
Annual grasses |
Perennial grasses |
Annual broadleaves |
Perennial broadleaves |
Comments |
||
|
Bentazon (Basagran) |
Post |
F |
P |
Tank mixes help |
||||
|
Bromoxynil (Buctril) |
Post |
G |
F |
Timing/temperature dependent; applied through chemigation |
||||
|
Carfentrazone (Aim) |
Pre |
P-G |
P |
|||||
|
Clethodim (Select Max) |
Post |
G |
F |
|||||
|
Clomazone (Command) |
Pre |
G |
P |
F |
P |
Susceptible to off-target movement |
||
|
Clopyralid (Stinger) |
Post |
E* |
G* |
*Depends on the weed |
||||
|
Diuron (Karmex/Direx) |
Pre |
P |
F-P |
P |
||||
|
Flumioxazin (Chateau) |
Pre |
E |
Dry weather can reduce efficacy |
|||||
|
MCPB (Thistrol) |
Post |
G |
Bindweed only |
|||||
|
Napropramide (Devrinol) |
Not widely used |
|||||||
|
Oxyfluorfen (Goal) |
Pre |
G |
Not used much outside the Willamette Valley; rainfall or overhead irrigation required to activate chemical |
|||||
|
Paraquat (Gramoxone Inteon, Firestorm) |
Pre |
E |
E |
|||||
|
Pendimethalin (Prowl H20) |
Pre |
F |
G |
|||||
|
Pyridate (Tough) |
Post |
E |
F |
|||||
|
Quizalafop (Assure II) |
Post |
E |
F |
|||||
|
Sethoxydim (Poast) |
Post |
G |
F |
Rainfall or overhead irrigation required to activate chemical |
||||
|
Sulfentrazone (Spartan) |
Pre/Post |
E |
P |
|||||
|
Terbacil (Sinbar) |
Pre/Post |
G |
F |
G |
P |
|||
|
Trifluralin (Treflan) |
Pre |
F |
P |
P |
P |
Must be soil incorporated |
||
|
Vapam |
Pre |
F |
F |
F |
F |
|||
|
Unregistered/new chemistries |
||||||||
|
Sharpen |
Pre |
E |
||||||
|
Zidua |
Pre |
G |
G |
G |
||||
Appendix N
Paul Jepson & Katie Murray, Oregon State University
The pesticide risk analysis is based on work by the Oregon IPM Center that forms the basis for a number of 3rd party certification standards for IPM (Jepson et al. 2020). We analyzed more than 650 pesticides, identifying those that were hazardous to human health, and those that posed manageable risks to aquatic life, wildlife, pollinators and bystanders. The analysis is intended to provide guidance that is supplementary to the pesticide label, which is the primary source of risk-management information and mandatory practices.
Risk to aquatic life
Pesticides qualified for this risk category if risks to one or more of the following risk models exhibited 10% or greater risk of an adverse outcome at a typical application rate: aquatic algae, aquatic invertebrates, or fish (reproduction).
Risk to terrestrial wildlife
Pesticides qualified for this risk category if risks to one or more of the following risk models exhibited 10 percent or greater risk of an adverse outcome at a typical application rate: avian reproduction, avian acute, or small mammal risk.
Risk to pollinators
Pesticides were selected based on a widely used hazard quotient (HQ) resulting of pesticide application rate in gallons of active ingredient per hectare, and contact LD50 for the honey bee (Apis mellifera). Values of the hazard quotient less than 50 have been validated as low risk in the European Union, and monitoring indicates that products with a hazard quotient greater than 2,500 are associated with a high risk of hive loss. The hazard quotient value (350 or greater) used by the Oregon IPM Center corresponds to a 15% risk of hive loss. The quotient includes a correction for systemic pesticides, where risks to bees are amplified.
Inhalation risk
Inhalation risk to bystanders was calculated using the ipmPRiME model for inhalation toxicity (Jepson et al., 2014), calculated on the basis of child exposure and susceptibility. This index is protective for workers who may enter fields during or after application, and also bystanders.
Jepson, P.C., Murray, K., Bach, O., Bonilla, M.A., Neumeister, L. (2020). Selection of pesticides to reduce human and environmental health risks: a global guideline and minimum pesticides list. Lancet Planetary Health 4: e56-53. https://doi.org/10.1016/S2542-5196(19)30266-9
