Best management practices for Christmas tree export

Heather Stoven, Chal Landgren, Luisa Santamaria, Helmuth Rogg and James LaBonte
EM 9093 | Published June 2014, Reviewed 2023 | | Order print copy

Exotic, invasive pests are a constant concern for trading partners around the world. The Pacific Northwest, like other regions, is continually monitoring for new pest introductions. However, as international trade grows, pest introductions are on the rise. This guidebook provides PNW producers and shippers of Christmas trees with the tools to both identify and manage some of the export pests of greatest concern to trading partners.

Export pests listed on countries’ quarantine lists do not fall into neat categories. Some are simply “hitchhikers” that do not harm trees, whereas others can cause cosmetic or other types of tree damage. Some were originally introduced into the PNW from outside regions, and others are native species. Generally, the only trait these pests have in common is that they can cause containers or trailers to be rejected at a port of entry.

This guidebook outlines best practices to help minimize the presence of pests of concern. With many pests, the best time for control is months or years before harvest. With others, careful attention during harvest can reduce problems. Regulatory officials have the right to reject loads if they find any pest of concern and not just those on official quarantine lists.

Christmas tree pests are frequently site-related, and their populations fluctuate. For example, Douglas-fir needle midge may be a problem for a few years on some fields and then become insignificant. Slug populations can be low one year and high the next. Twig weevils can be an issue on some trees on dry sites and rarely seen in other locations. Due to this variability, growers should review this guidebook frequently.

This guidebook explains best practices for identifying and managing the most common pests causing rejection of Christmas trees shipped from Oregon: slugs, Douglas-fir needle midges, yellowjackets, root weevils and Douglas-fir twig weevils. For each pest, the following topics are covered:

  • General pest information describes pest identification, biology and life cycle.
  • Scouting and monitoring describes where to look for pests during growing years and at harvest. In addition, thresholds for particular trading partners are listed.
  • Management describes how to control pests during growing years and at harvest.
  • Calendars show the time frame for pest life cycle and management.
Section anchor "slug"

Slug

Arion spp. and Deroceras spp.

General pest information

Pest identification

  • Mollusks without shells; variable in size and coloring. (See Terrestrial Mollusk Tool for identification resources.)
  • In Oregon, there are around 10 species of pest slugs (all of which are exotic, invasive species).

Biology and life cycle

  • Most active in October, November and late February to May, depending on moisture and temperature
  • Generally not feeding December through early February (bait may be less effective during these times)
  • Feeding on weeds, seeds, lichens, fungi, decaying vegetation and other organic materials in Christmas tree fields
  • Mating and egg laying occurs during active periods:
  • Eggs are about 1 to 6 millimeters (1∕25 to 1⁄4 inch) in diameter, round or oval, transparent, golden or white (depending on the species).
  • Eggs hatch after two to four weeks; those laid in October often overwinter until February.
  • Possibility of overlapping generations

Scouting and monitoring

Growing years

  • Look in weedy areas of the field.
  • Scout around trees in the field in the evenings, early morning or at night.
  • Look in moist, protected areas during the day. Place pieces of plywood (2' × 2' or 3' × 3') in weedy areas and lift to find sheltering slugs; monitor population trends. (See "Overview of trapping and monitoring options.")
  • Trap and scout after light rains and when night temperatures are above 50° F (10° C).
  • Scout more actively during mild, wet winters or wet springs.

At harvest

  • Look at interior of tree.
  • Check in weedy areas of field, fencerows, etc.
  • Monitor more intensively during wet periods.

Threshold

  • Some trading partners, such as Hawaii and Japan, have zero tolerance for slugs.

Management

Growing years

  • Remove weeds wherever possible.
  • Place bait in the spring and fall, when moisture is present and temperatures are above 50° F (10° C). Always review current label before use.
  • Apply bait every 10 to 14 days when slugs are active; reapply if mold forms. Scout for slug mortality.
  • Apply bait in growing and handling areas the year prior to harvest; apply following a spring rain.
  • Apply bait evenly to the ground; do not pile bait.
  • Encourage and conserve slug predators, such as ground beetles, by avoiding broad-spectrum insecticides.

At harvest

  • Shake trees according to compliance agreements for destination countries. (See "Best management practices at harvest.")
  • Limit the time trees touch the ground. Do not leave harvested trees on the ground overnight, if possible.
  • Place trees on pallets to keep them off the ground at harvest.
  • Apply slug bait around landing and loading areas following a rain.
  • Do not put slug bait in containers — this is illegal. Also, slugs do not feed at 34° F (1° C) container temperatures.

Calendars

Life cycle

  • Look for active egg laying: February through April and October through November
  • Eggs will hatch in favorable conditions: January, May through September and December
  • Adults and juveniles are present, but not active: January, June through September and December
  • Adults and juveniles are active: February through May and mid-October through November

Management

  • Scout weedy areas: February through June and mid-September through November
  • Apply slug bait: Mid-February through June and October though November
Section anchor "midge"

Douglas-fir needle midge

Contarinia pseudotsugae, C. constricta, C. cuniculator

General pest information

Pest identification

  • Adults are small orange flies 2 millimeters (1/16 inch) long.
  • Yellow-brown to orange-colored eggs, each with a red spot, can be seen with a 16× hand lens on new needles and buds.
  • Legless larvae are 2 millimeters (1/16 inch) long with white, yellow, orange or olive-green bodies, and no distinct head.
  • Contarinia pseudotsugae, C. constricta and C. cuniculator are all very similar in appearance and behavior.

Biology and life cycle

  • Adults typically emerge in April to May and lay eggs on buds and new growth. Larvae emerge after a few days and burrow into needles, forming galls, where they spend the summer.
  • In fall, larvae emerge from galls, drop to the ground and enter the soil.
  • In spring, larvae pupate in soil before adult emergence.
  • Individual adults live only a few days; however, emergence occurs over several weeks.

Scouting and monitoring

  • Only affects Douglas-fir

Growing years

  • Monitor for adult Douglas-fir needle midge emergence to effectively time spray applications. (See “Overview of trapping and monitoring options.”)
  • Use the USPEST.ORG online phenology and degree-day model for Douglas-fir needle midge to predict adult emergence.
  • Place five traps per field or 10 per acre; check frequently to time sprays, if needed.
  • Record locations of needle damage found in late summer to scout and place traps accordingly the following spring.
  • Note: Traps will collect insects other than needle midges, including non-pest species of midges.

At harvest

  • Douglas-fir needle midge is in larval stage feeding inside the needles.
  • Feeding damage includes yellowish swellings (galls), yellowing needles and premature needle drop.

Threshold

  • Some trading partners, such as Mexico, have zero tolerance for selected species of Douglas-fir needle midges.

Management

Growing years

  • Remove and destroy heavily infested trees in the early fall, before larvae exit needles.
  • Time insecticide application based on collection of adults in emergence traps, field scouting or the USPEST.ORG online phenology and degree-day model for Douglas-fir needle midge.
  • Make first insecticide application based on collections in traps, scouting, weather, and bud development.
  • Note: Insecticides are effective only against adults. (Visit the PNW Insect Management Handbook.)

At harvest

  • Exclude trees with signs of Douglas-fir needle midge damage when shipping internationally.
  • C. constricta is the only species on the Mexican quarantine list; however, try not to ship any damaged trees, since misidentification is likely and Douglas-fir needle midges have caused the most load rejections by Mexico. (See “Pest quarantine information.”)
  • Note: Shaking is not 100% effective, and infested needles may remain on trees.

Calendars

Life cycle

  • Look for eggs: April through May
  • Look for larvae in soil: January through February
  • Look for larvae in needles: June through September
  • Look for larvae in soil: October through December
  • Look for pupae: March through April
  • Look for adults: April through May

Management

  • Swollen and yellow needles present: June through December
  • Place emergence traps: mid-March through mid-May
  • Apply spray control measures based on monitoring: mid-April through mid-June
  • Remove infested trees: August through mid-October
  • Keep visibly infested trees from international shipments: mid-October through mid-November
Section anchor "yellowjacket"

Yellowjacket

Vespula pensylvanica, (Western yellowjacket), Vespula germanica (German yellowjacket), Vespula vulgaris (Common yellowjacket)

General pest information

Pest identification

  • Workers are approximately 13 millimeters (one-half inch) long; queen is 18 millimeters (three-quarters inch) long.
  • Black and yellow in color
  • German yellowjacket, though not common in Oregon Christmas tree fields, is the only wasp on the quarantine pest list for Mexico. (See “Pest quarantine information.”)
  • All Vespula yellowjackets are quarantine pests for Hawaii. (See “Pest quarantine information.”)

Biology and life cycle

  • Yellowjackets feed on insects, nectar, honeydew and fruit.
  • Workers can fly up to 400 meters (1/4 mile) in search of food.
  • Yellowjackets are social insects with one queen per colony and often hundreds to thousands of workers.
  • Queen overwinters in protected locations.
  • Overwintering queen typically emerges in May.
  • After emergence, queen builds nest above or below ground and begins to produce workers.
  • Queen stays in nest through the growing season.
  • In August through October, new males and queens are produced.
  • Queens with fertilized eggs search for an overwintering site in October or November.
  • Queens and males may be active during shipping season, and queens may seek shelter in baled trees.

Scouting and monitoring

Growing years

  • Look for yellowjackets attracted to honeydew in aphid-infested trees.
  • Yellowjacket traps can be placed in the field for monitoring. (See “Overview of trapping and monitoring options.”)
  • Look for nests in the field and surrounding areas.

At harvest

  • Look within branches and around baled trees stacked for shipping.

Threshold

  • Some trading partners, such as Mexico and Hawaii, have zero tolerance for some or all yellowjacket species.

Management

Growing years

  • Trapping in the spring kills queens and prevents nest building, whereas trapping in the summer and fall kills workers and reduces populations.
  • Chemical lures/attractants are species-specific; food attractants are not.
  • Treat nests with approved insecticides.
  • Manage other pests, such as aphids, that attract yellowjackets.

At harvest

  • Shake trees according to compliance agreements for destination countries. (See “Best management practices at harvest.”)
  • Remove shaking debris frequently and keep debris separate from trees so pests are not reintroduced.
  • Apply approved pyrethroid sprays to trees in the field three to six weeks prior to cutting to meet current requirements for Mexico. Note: These sprays should not be relied upon as the only control method and may cause secondary pest outbreaks.
  • Exclude yellowjackets from trucks on warm days by closing trailer doors or using netting.
  • Minimize the time that trees remain in stacks. A second shaking just prior to loading can be effective.
  • Do not put “bug bombs” in Christmas tree containers — this is illegal.

Calendars

Life cycle

  • Look for eggs: May through October
  • Look for males: August through October
  • Look for queens: all year

Management

  • Scout fields for presence of workers and nests: June through August
  • Trap queens: in May
  • Trap workers and treat nests: June to September
  • Shake harvested trees: October through November
Section anchor "root-weevil"

Root weevil

Barypeithes pellucidus, Sciopithes obscurus, Nemocestes spp. and Otiorhynchus spp.

General pest information

Pest identification

  • Adults are 2 to 11 millimeters (1∕16 to 1∕2 inch) in length.
  • Typically brown or black in color
  • Larvae are C-shaped, legless grubs with a brown head and white body.

Biology and life cycle

  • Root weevils can cause significant crop loss as well as cause load rejection for Christmas tree exporters.
  • Late-stage weevil larvae are present in late spring and summer.
  • Larvae feeding on tree roots cause the most damage.
  • Pupae occur from late May into early June.
  • Adults are present year round.
  • Adults typically feed on needles at night.
  • Adults can girdle seedlings and small trees.
  • Adults lay eggs in soil four to six weeks after their emergence.
  • Individuals of most species are all egg-laying females.
  • There is one generation per year.
  • Barypeithes pellucidus and Otiorhynchus spp. were accidentally introduced from Europe. Nemocestes spp. and Sciopithes obscurus are native.

Scouting and monitoring

Noble fir most susceptible, followed by Douglas-fir, grand fir, Nordmann fir and Turkish fir

Growing years

  • Look for adults on cloudy days and at night on branches and trunks; use beating boards and sheets. (See “Overview of trapping and monitoring options.”)
  • Look for notching of needles and girdling of small trees and branches (evidence of adult feeding).
  • Place pitfall traps in the field for monitoring. (See “Overview of trapping and monitoring options.”)
  • Check for adults during the day under pieces of plywood placed on the ground overnight (similar to slug monitoring).
  • Dig with a shovel around roots to monitor for larvae.
  • Note: Evidence of digging by insect-eating mammals can be an indication of the presence of larvae.

At harvest

  • Look for adults on trees that show evidence of notching on needles.
  • Look for adults on cloudy days or at night on branches and trunks.
  • Use pitfall traps or check under pieces of plywood placed on the ground.

Threshold

  • Some trading partners, such as Mexico, Japan and Hawaii, have zero tolerance for some or all root weevil species.

Management

Growing years

  • Apply pesticides as adults become active and before egg laying occurs. (Visit the PNW Insect Management Handbook.)
  • Apply labeled insecticide in the evening during peak adult activity in May to June.
  • Disrupt habitat (for example, by disking or tilling in the summer and fall) to reduce populations.
  • Reduce shelter and additional hosts by controlling weeds around loading areas.
  • Preserve populations of rove and other naturally-present ground beetles, as they can be important biological control agents.
  • Note: Nematodes and fungi have been used as biocontrol agents in Christmas trees.

At harvest

  • Shake trees according to compliance agreements for destination countries. (See “Best management practices at harvest.”)
  • Keep trees off the ground at harvest, especially after shaking. Trees left overnight on the ground are very vulnerable to root weevil infestation.
  • Do not place trees near shaking debris; remove debris frequently.

Calendars

Life cycle

  • Look for eggs: mid-July through mid-August
  • Look for larvae: mid-August through June
  • Look for pupae: May through June
  • Look for adults: all year

Management

  • Notched needles present: June through mid-November
  • Monitor for larvae by digging: April through May
  • Monitor for adults with traps/boards or by scouting at night: June through September
  • Apply biocontrol: April through May
  • Apply foliar insecticide sprays: May through June
  • Disrupt habitat by disking or tilling: September through the beginning of October
Section anchor "twig-weevil"

Douglas-fir twig weevil

Cylindrocopturus furnissi

General pest information

Pest identification

  • Adults are 2 to 3 millimeters (1∕10 inch) long.
  • Bronze-colored (sometimes spotted) with long beaks
  • Larvae are legless, white, C-shaped grubs.

Biology and life cycle

  • Adults emerge between mid-June and early August but can be present throughout the year.
  • Adults feed on the inner bark of new twigs.
  • Eggs are laid in punctures in twigs and branches about a month after adult emergence.
  • Larvae bore in Douglas-fir twigs, branches, and leaders.
  • Pupation occurs in April through mid-July.
  • Larvae can be present throughout the year.
  • One generation and a partial second generation occur each year.

Management

Growing years

  • Control from July to early August, when most adults emerge; be aware that adults can be present any time. (Visit the PNW Insect Management Handbook.)
  • Maintain vigorous growth.
  • Avoid planting or replanting stress-prone sites.
  • Remove or destroy infested trees.
  • Prune out damaged branches.

At harvest

  • Identify and remove trees with damage.
  • Do not ship unhealthy, damaged trees.

Calendars

Life cycle

  • Look for eggs: July through mid-August
  • Look for larvae: all year
  • Look for pupae: April through mid-July
  • Look for adults: all year

Management

  • Dead branches present: all year
  • Look for larvae actively tunneling in twigs, branches and leaders: mid-January through the beginning of May
  • Control adults: July through August
  • Remove dead branches and trees: September through October
Section anchor "harvest"

Best management practices at harvest

Harvest time is hectic, and logistics can be challenging. In planning for harvest, include pest mitigation practices related to baling, shaking, tree care and storage. Below are some steps to consider in your harvest planning process.

Baling and shaking

Regulations for Mexico

Current regulations for Mexico call for tree shaking for 15 seconds. A number of details can improve (or reduce) the effectiveness of shaking.

  • Prune tree bases to sufficient height to fit in the receiving cone on the shaker. Otherwise, if the stiff lower branches sit on top of the cone, they act as shock absorbers and reduce the shaking efficiency.
  • Clean out the receiving cone on the shaker frequently. The cone can quickly fill with needles. If the needles are allowed to build up, they act as a shock absorber and minimize the effect of shaking. Some receiving cones have openings on the sides to allow debris to shake out automatically; this can be an effective feature.

Debris piles

Besides containing dead needles, debris piles contain pests previously shaken off. These pests can migrate to piles of harvested trees and cause recontamination. Move your shaking operation away from the landing area or frequently remove the piles of debris. At the loading site, separate the debris piles and the trees, and remove the debris often.

Tree care and storage

Some pests (e.g., snails, slugs and beetles) may move from the ground to the tree after cutting. Minimize the time trees are in contact with the ground (e.g., place the trees on pallets).

Other pests, such as yellowjackets, can fly into piles of shaken, baled trees before or during the loading of trees into trailers. This is particularly a problem on warm, dry days, when yellowjacket queens are looking for overwintering sites and are not attracted to baits. Growers’ control options are limited, but some helpful steps include:

  • Minimize the time trees remain in piles
  • Control the populations of yellowjackets around loading areas beginning in May
  • Put netting around trees in piles and screening on trailer loading doors
Section anchor "quarantine"

Pest quarantine information

This pest guide focuses on the most common insects intercepted on Christmas trees from Oregon. For Mexico this includes: Douglas-fir needle midge, Douglas-fir twig weevil, root weevils and yellowjackets. For Hawaii the most commonly intercepted pests are slugs.

Different shipping destinations list different pests for quarantine. Thus, it is essential to identify and closely adhere to shipping requirements. Check your state’s Department of Agriculture website to learn about shipping regulations and pest quarantine lists.

Pests of concern for Hawaii, Florida, North Carolina, Virginia and Mexico are listed below. Check your state’s Department of Agriculture website to learn more about these destinations and access quarantine lists for other destinations.

Hawaii

Slugs, snails and yellowjackets (Vespula spp.)

Florida, North Carolina and Virginia

European brown garden snail (Cornu aspersa, also known as Helix aspersa)

Mexico

Pests of concern for Oregon pines and spruce:

  • Rhyacionia buoliana (European pine shoot moth)
  • Pissodes strobi (White pine weevil)

Pests of concern for Oregon Douglas-fir and noble fir:

  • Cylindrocopturus furnissi (Douglas-fir twig weevil)
  • Contarinia constricta (Douglas-fir needle midge)
  • Vespula germanica (German yellowjacket)

Mites of concern:

  • Nalepella ednae (Eriophyid mite)
  • Epitrimerus pseudotsugae (Eriophyid mite)

Note: Mexico has pests on its quarantine list that are either not known to exist in Oregon or are not typically pests of Oregon Christmas trees.

Pests not known to exist in Oregon:

  • Choristoneura fumiferana (Eastern spruce budworm)
  • Diprion similis (Pine sawfly)
  • Lymantria dispar (Spongy moth)
  • Tomicus piniperda (Pine shoot beetle)
  • Paradiplosis tumifex (Balsam gall midge)

Insects not typically pests of Oregon Christmas trees:

  • Choristoneura occidentalis (Western spruce budworm)
  • Orgyia pseudotsugata (Douglas-fir tussock moth)

Legal considerations for exporting

Export markets provide economic opportunities but come with added challenges and responsibilities. If you are thinking about exporting out of state or to foreign countries, there are a number of requirements relating to inspections and documentation.

The place to start for information on export requirements is the Department of Agriculture in the state where your trees are grown. Oregon and Washington both require Christmas tree growers above a certain size to have a grower’s license. Even if you sell through a broker or another grower, you need a license and your broker is required to list where the trees came from.

Shipping to foreign countries and a few domestic destinations requires an electronically-filed application on the phytosanitary certification issuance and tracking system (PCIT). This process requires a number of steps, so allow time to complete them. Briefly, to complete the PCIT process:

  • Log on to the USDA PCIT web site
  • Create a USDA eAuthentication account.
  • Link your new account to the PCIT.
  • Create a PCIT account for your organization/farm or join an existing organization.

When states, like Hawaii, require phytosanitary certificates, federal PCIT certificates are used. Do not confuse a shipping permit with a phytosanitary certificate. All shipments require shipping permits (available upon request from your Department of Agriculture), but only a few destinations also require phytosanitary certificates.

At a minimum, all loads of shipped trees require that bills of lading, invoices and bills of sale indicate county of origin, as well as the name and address of the shipper. Oregon law requires that a shipping permit accompany Oregon loads.

Review the web site of your Department of Agriculture and be aware of the compliance and inspection needs for the species you grow and the destinations where you want to ship. Keep in mind that control of some pests can require years of effort prior to your first load of shipped trees.

Section anchor "trapping"

Overview of trapping and monitoring options

Trapping and monitoring are not required for export inspections, but they can be helpful in timing control, knowing what pests are present, and avoiding surprises. To that end, it is important to know where and how to set traps. Traps that are poorly placed or set out at the wrong time can give incorrect information and a false sense of security.

Pitfall trap

Pitfall traps attract and trap a wide variety of ground crawling creatures. These traps are often covered with small boards with runners underneath to keep out rain and dirt. These traps are useful in checking for slugs, snails, root weevils and ground beetles. They are a non-specific trap because anything that passes by can be captured.

Slug and snail trap

For attracting and trapping slugs and snails, place beer or baking yeast in a 5% sugar-water solution in a pitfall trap or a pan set in the ground. Growers shipping to areas with slug or snail restrictions often bait areas where trees are stored and can use traps to monitor the presence or absence of mollusks.

Sticky monitoring traps

Sticky monitoring traps are highly adhesive, water-resistant tags of various sizes and colors that insects adhere to when they fly into them. Various chemical lures and bait attractants are available, though few are specific to Christmas tree pests. These traps can be useful in monitoring Douglas-fir needle midge; however, they may also trap a variety of non-pest midges and other flying insects.

Funnel trap

Funnel traps are made of nested black funnels (up to as many as 12). Insects fall through the funnels to a cup that is filled with a preservative. Funnel traps come in a wide range of sizes. Flying beetles and other insects may be attracted by chemical lures and captured in the trap base. Few lures specific to Christmas tree pests are currently available.

Yellowjacket attractant traps

Yellowjacket attractant traps include chemical lures, colors and trap designs to attract western yellowjackets. These traps are less successful with German yellowjackets. They are useful for monitoring worker activity but not for control.

Yellowjackets are the only Christmas tree “pest” for which there are specific chemical lures for attraction. Placing roughly five traps per 10 acres of field is sufficient for monitoring. The queen is the key to controlling population growth, and she only flies in March. Thus, early lure placement and trapping should help control some colony formation. Since the queen does not move outside the nest after this early period, later trapping only affects the worker population. There are currently no registered insecticides that may be used as toxic bait to eliminate the nest. Direct spraying of ground nests is allowed; traps may be useful in finding these ground nests. Ground nests can pose hazards to shearing crews and visitors, so control is also beneficial for safety.

Board trap

A raised board trap with runners that is placed in a field provides a hiding place for slugs. Board traps without runners are effective for root weevil monitoring. For root weevils, the board should be placed lightly on the ground to allow space for the insect to shelter. Board traps are good monitoring tools because slugs and root weevils seek dark, protected sites during the day.

See the sections on slugs and root weevils for suggestions on the timing and placement of traps.

Needle midge traps

Needle midge traps consist of a box with a jar inserted into the top edge of one side. As adults emerge from the soil, they fly towards the light (jar) to escape. Place a moist towel inside the jar to catch the adult midges. The jar will contain other flying and crawling insects, so use a hand lens to help with identification.

See "Douglas-fir needle midge" for suggestions on the design and timing of traps.

Pay particular attention to Douglas-fir fields that had Douglas-fir needle midge problems the previous year and to edge rows close to native Douglas-fir timber. Needle midges seem to prefer the “shady side” of trees, where there may be some vegetation; however, in a fully stocked field, this could be anywhere. The needle midge is one of the few pests for which there are degree-day models to track emergence, which can vary by four to five weeks from year to year (See "Resources"). The degree-day models can help determine when to place traps. Placing five emergence traps per field of trees is good for monitoring a growing area. Place the traps with the jar side facing between rows so it gets as much light as possible. Check the traps frequently and count needle midges to get an idea of population numbers. Prolonged cool rain during emergence also helps control numbers.

Insect sweep nets

Insect sweep nets are useful for capturing flying insects, such as Douglas-fir needle midge.

Beating boards and sheets

Beating boards and sheets are used beneath limbs to sample insects, such as adult weevils, that are easily knocked off.

Hand lens

Many pests are too small to see unaided. A hand lens with 10× or 16× magnification will help identify these insects.

Section anchor "resources"

Use pesticides safely!

  • Wear protective clothing and safety devices as recommended on the label. Bathe or shower after each use.
  • Read the pesticide label—even if you’ve used the pesticide before. Follow closely the instructions on the label (and any other directions you have).
  • Be cautious when you apply pesticides. Know your legal responsibility as a pesticide applicator. You may be liable for injury or damage resulting from pesticide use.
Section anchor "authors"

Acknowledgments

The authors thank the following peers for the review of these diagnostic cards and for their helpful comments and suggestions. In alphabetical order:

  • Todd Adams, Oregon Department of Agriculture
  • Michael Bond, Oregon State University
  • Gary Chastagner, Washington State University
  • Kirk Company, Oregon City, OR
  • Judy Kowalski, Oregon State University
  • Dionisia Morales, Oregon State University
  • Robin Rosetta, Oregon State University

About the authors

Helmuth Rogg
James LaBonte

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