understanding and managing wisconsin’s most menacing

University of Wisconsin: Insect Diagnostic Lab

Understanding and Managing Wisconsin’s Most Menacing

Landscape Insect Pests of 2020

PJ Liesch UW-Insect Diagnostic Lab

Twitter: @WiBugGuy [email protected]

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University of Wisconsin–Madison Insect Diagnostic Lab

Topics in Today’s Presentation:▪ Trending or significant plant pests from 2020 ▪ EAB, viburnum leaf beetle, gypsy moth, Japanese beetle, etc.

▪ Other notable insects ▪ Minor/occasional pests, in the news

▪ On the radar: pests to watch for

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Emerald Ash Borer (Agrilus planipennis)

Six new county-level detections in 2020: Dunn, Florence, Oconto, Pepin, Price, Shawano

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Map Sources: WI-DATCP

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EAB Biocontrol Efforts▪ 2021: USDA ending federal

quarantine; shifting efforts to biological control

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Spathius agrili

Oobius agrili

Tetrastichus planipennisi

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EAB Chemical Controls

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Viburnum Leaf Beetle (Pyrrhalta viburni)▪ Leaf beetle native to Europe; introduced to eastern Canada 1940’s

▪ Northeast US in 1990’s; Wisconsin in 2014

▪ Also in Pacific NW

▪ Adults and larvae skeletonize foliage of viburnum shrubs

Larva: ~1/3” long; pale with pattern of spots; dark head capsule and 6 legs

Adults: ~1/4” long; yellowish-green colour

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Trending: Viburnum Leaf Beetle

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VLB Damage

Skeletonization damage

Severe damage

Oviposition damage (twigs)

▪ Both larvae and adults feed on foliage ▪ Adult ♀ also chew pits in twigs

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Viburnum Leaf Beetle Biology▪ ONE year life cycle ▪ Overwinter as eggs; larvae emerge in April/May and feed ▪ Larvae walk down to soil to pupate; adults emerge in June/July ▪ Adults feed and ♀ lay up to 500 eggs (in pits of 5-8 eggs)

Oviposition pits

Larval feeding and skeletonization

Mating Adults

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Viburnum Leaf Beetle Management▪ Cultural

▪ Choosing less-susceptible cultivars ▪ Maintain plant vigor

▪ Physical ▪ Prune out egg sites ▪ Removal/replacement of damaged plants

▪ Biological ▪ Limited research to date

▪ Chemical ▪ Foliar insecticide sprays targeting

larvae in spring and adults in summer ▪ Systemic insecticides in spring

Cultivar Selection

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Lily Leaf Beetle (Lilioceris lilii)▪ Also known as the “scarlet lily beetle”

▪ Leaf beetle native to Europe; introduced to eastern Canada 1940’s

▪ Northeast US in 1990’s; Wisconsin in 2014

▪ Cause significant damage to true lilies (not daylilies)

Adults: ~1/3” long; bright red colour; “squeak” when picked up

Larvae: ~1/3” long; yellow body; cover themselves with excrement giving a slimy appearance

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Trending: Lily Leaf Beetle

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Lily Leaf Beetle Host Plants▪ True lilies: Asiatic, Oriental, Easter, Turk’s cap, Tiger, & Wood lilies ▪ Also eat: Fritillaries & Solomon’s Seal

▪ Don’t eat canna lilies, calla lilies, or daylilies

Solomon’s Seal

True lilies

Fritillaries

Calla LilyCanna Lily

Daylilies14

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LLB Damage▪ Both larvae and adults feed on foliage

Damage of small larvae

Severe damage

Holes in leaves

Adult Feeding15

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Lily Leaf Beetle Biology▪ ONE year life cycle ▪ Overwinter as adults; mate and lay eggs in spring ▪ Larvae feed and camouflage themselves; head to ground to pupate ▪ Adults feed and ♀ lay 400+ eggs (in batches of 8-12)

Eggs

Mating Adults (Spring)

Larvae

Cocoon Stage (in soil)

Winter

Adults (mid-summer)

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Lily Leaf Beetle Management▪ Cultural

▪ Choosing less-susceptible species/cultivars ▪ Maintain plant vigor

▪ Physical ▪ Hand-picking or squishing ▪ Removal/replacement of infested plants

▪ Biological ▪ Parasitoid wasps released in northestern US ▪ Limited impact thus far

▪ Chemical ▪ Contact insecticide sprays targeting larvae and/or adults

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Gypsy Moth (Lymantria dispar)▪ Native to Europe and northern Asia; introduced in 1860’s ▪ Range expanding westward and southward ▪ Outbreaks at leading edge of expansion

▪ Major defoliator of hardwood trees ▪ Significant invasive species!

Gypsy Moth Caterpillar: Up to ~2” long

Gypsy Moth Adult Female w/Egg Mass:

~1.5” long

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Trending: Gypsy Moth▪ Distinct uptick in gypsy moth numbers in 2020 ▪ DATCP: GM populations are “intermediate”

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Recent Trends:

▪ Why was gypsy moth activity up in 2020?

▪ Mild winter 2019-20 (decreased egg mortality)

▪ Drier conditions in 2020 (decreased Entomophaga)

▪ What to expect in 2021…???

▪ Polar vortex impacts

▪ Spring weather patterns impact Entomophaga

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Gypsy Moth Quarantines

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Gypsy Moth: Physical Control▪ Egg Masses: inspect for and scrape away ▪ Late summer through the following spring

▪ Sticky Band: to target very young caterpillars ▪ Burlap Band: to target larger caterpillars, which hide during the day

Burlap Band Method

Sticky Band Method

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Gypsy Moth: Biological Control▪ Fungus: Entomaphaga maimaiga ▪ Brought from Japan in early 1900’s; not effective until 1980’s! ▪ Spores are spread via wind; infects young larvae

▪ Virus: NPV ▪ Can be transmitted to eggs by ♀

▪ Predators/Parasites: ▪ Parasitoid wasps & flies ▪ Predatory ground beetles & stink bugs ▪ Mice

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Gypsy Moth: Chemical Control▪ Conventional foliar sprays: acephate, bifenthrin, carbaryl,

chlorantraniliprole, cyfluthrin, cypermethrin, deltamethrin, lambda-cyhalothrin, permethrin, spinosad, …

▪ Systemic products: acephate, chlorantraniliprole, clothianidin

▪ Alternative products: Bacillus thuringiensis kurstaki (Btk), SPLAT-GM (pheromone), insecticidal soap, horticultural spray oil

Mating Disruption with SPLAT-GM

Aerial spraying with Btk

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Japanese Beetle (Popillia japonica)▪ Scarab beetle from Japan; detected in New Jersey in 1916

▪ Found across much of eastern US; some pockets in West

▪ Adults: above ground foliar feeder

Adults: ~1/3” long; copper & green colored; white spots along side of body Larva: soil-dwelling white grub

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Trends in Wisconsin

Map Credit: Google Maps

▪ Well established in southern WI ▪ Can occur in “pockets”

▪ Gaining footholds in northern WI

▪ Populations highly variable in 2020

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Japanese Beetle Biology▪ ONE year life cycle

▪ Adults emerge ~June/July in Midwest; active into September

▪ Adults are sun-loving, gregarious insects; strong fliers

▪ Adults are skeletonizers, NOT true defoliators

▪ Attack 350+ plant species; can feed on leaves/fruit/flowers▪ Lindens

▪ Roses

▪ Birch

▪ Grapes

▪ Beans

▪ Apple/Crabapples

▪ Cherries

▪ Maples

▪ Elms

▪ Hibiscus

▪ Horsechestnut

▪ Willows

▪ Corn

▪ Asparagus…

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Japanese Beetle Damage

Significant Japanese beetle DamageFeeding on flowers

Skeletonization

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Managing Japanese Beetles & Their Damage

Management Scenarios: 1. Turfgrass 2. “Small” plants (gardens, flowers, shrubs, small trees) 3. “Large” plants (trees)

▪ Many factors can influence management approaches: ▪ Time/worker availability? ▪ How many plants are affected? ▪ How large of an area? ▪ Size of the plants? ▪ Preferences—aesthetics, organic, etc.

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Japanese Beetle: Cultural Control▪ Manipulation of the local environment to prevent pest

problems or reduce the amount of damage

▪ Plant location in the landscape

▪ Choosing less-preferred plants

▪ Maintain plant vigor

▪ Tolerance

▪ Turf: proper turf care (fertility, mowing, irrigation)

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Japanese Beetle: Physical Control▪ Physical activities performed to help prevent or reduce pests

▪ Hand-picking ▪ Squishing ▪ Barriers/row cover ▪ Traps

Photo Credit: Whitney Cranshaw, Bugwood.org

Photo Credit: Aaron Baugher, via flickr

Traps: helpful for monitoring; little/no meaningful control of Japanese beetles in most situations

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Japanese Beetle: Biological Control▪ Many natural enemies feed on or attack Japanese beetles,

but don’t have much overall impact: ▪ Predators

▪ Parasites

▪ Pathogens

Parasite: Winsome Fly

Photo Credit: Whitney Cranshaw, Bugwood.orgPhoto Credit: David Cappaert, Bugwood.org

Pathogen: Milky Spore Disease

(Paenibacillus popilliae)

Predator: Crow digging for grubs

Photo Credit: Marie-Lan Nguyen via Wikipedia

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Chemical Controls

▪ Each approach uses different products and/or tactics

▪ Targeting one life stage has small impacts on the others

▪ Focus on the plant(s) you’re trying to protect

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Chemical Control: Small Plants▪ Foliar applications of contact insecticides typically used ▪ Applications to blooming flowers pose risks to pollinators ▪ Short residual activity

▪ Carbaryl ▪ Bifenthrin ▪ Cyfluthrin ▪ Cyhalothrin ▪ Cypermethrin ▪ Deltamethrin ▪ Permethrin ▪ Chlorantraniliprole

ConventionalOrganic

▪ Insecticidal soap* ▪ Horticultural oils (neem, etc.)*

▪ Azadirachtin ▪ Pyrethrins ▪ Bacillus thuringiensis galleriae

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Large Plants (Trees); Certain Shrubs▪ Systemic products can be applied preventatively ▪ Typically applied as a soil drench ▪ Ex. Imidacloprid

▪ Can take several weeks for uptake in large trees

▪ Can pose risks to bees ▪ Wait until after plants have bloomed to apply if possible ▪ Can’t use on lindens due to pollinator concerns

Do not apply this product, by any application method to linden, basswood, or other Tilia species

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Dogwood Sawfly (Macremphytus tarsatus)▪ Native pest with a single generation in mid-late summer ▪ Wasp-like adults; larvae feed on dogwoods (Cornus spp.)

Larvae: up to ~1” long

Black and yellow coloring; often covered by whitish waxy coating Adult

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Dogwood Sawfly Damage▪ Only feed on dogwoods (Cornus spp.)

▪ Chew notches in leaves; consume entire leaves ▪ Occasional complete defoliation; plant death rare

▪ Wood damage to homes/structures occasionally observed…

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Dogwood Sawfly Life Cycle

▪ Overwinter as pupae

▪ Adults emerge May-July ▪ Mate and lay eggs in

▪ Larvae typically noticed in mid-late summer

▪ Leave plants to excavate small pupal chamber in soft wood

Only one generation per year

Eggs laid in dogwood leaves

Dogwood sawfly larvae

Adult Dogwood Sawfly

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Dogwood Sawfly Control▪ Cultural

▪ Maintain plant vigor ▪ Choose non-preferred hosts (they only like dogwoods…)

▪ Physical ▪ Physically remove or squish larvae (check undersides of leaves)

▪ Chemical ▪ Conventional foliar sprays: acephate, bifenthrin, carbaryl, cyfluthrin,

cypermethrin, deltamethrin, lambda-cyhalothrin, permethrin ▪ Low impact sprays: insecticidal soap, light horticultral oils, pyrethrins,

neem oil, spinosad ▪ Bacillus thuringiensis kurstaki (BTK) won’t work (not a true caterpillar!)

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Magnolia Scale▪ Host plant: Magnolias ▪ Covered with a waxy powder ▪ Major problems in 2015 & 2016 ▪ Increased pressure in 2019 & 2020

Credit: William Fountain, Bugwood.org

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Soft Scales▪ Lack detachable cover

▪ Often with plump appearance ▪ High reproductive capacity ▪ Produce lots of honeydew

▪ Can attract ants, wasps, sap beetles, etc. ▪ Growth of black sooty mold

Credit: Lacy L. Hyche, Bugwood.org

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Timing is Everything!▪ Juveniles (“crawlers”)—most vulnerable life stage ▪ Insecticide sprays targeting crawlers can be very effective ▪ Many species can be predicted using Growing Degree Days

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Scouting: • Magnified examination • “Notepad” method • “Tape” method

GDD: 2155 - 2800 Date: Late August - September

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Magnolia Scale Control▪ Physical Control: ▪ Remove heavily infested plants ▪ Selectively prune heavily infested portions of plants

▪ Chemical Control: ▪ Dormant oil ▪ Contact insecticides (2100-2800 GDD) ▪ Systemic products

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Magnolia Scale Biological Control▪ Several generalist predators can feed on scale insects ▪ Specialized parasitoid wasp can cause high mortality ▪ Outbreaks typically controlled within a few years ▪ Beneficials can be impacted by insecticides

Parasitoid Wasp

Predatory Lady Beetle Larvae

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▪ Several species in the Midwest ▪ Occasional pest

▪ Numerous hosts: azaleas, oak, elm, birch, crabapple, linden, aspens, willows, roses, and others

▪ White or black colored; wings with lace-like pattern; adults ~1/8-1/4” ▪ Nymphs smaller and spiky

▪ Typically overwinter as adults (and some eggs); multiple generations per year; can be found into the fall

Adults Nymphs

Lacebugs (Tingidae)

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▪ Yellowing or stippling of foliage ▪ Can resemble spider mite

damage ▪ Black fecal spots often present

▪ Often on undersides of leaves

▪ Commonly controlled with contact insecticides

Lacebug Damage & Control

Stippling Damage

Lacebug Nymphs on Underside of Leaf

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On the Radar: Box Tree Moth▪ Invasive pest from Asia; introduced to Europe 2006 ▪ By 2020: have decimated boxwoods around Europe

▪ Detected in Canada: Toronto, Canada 2018 ▪ Caterpillars defoliate plants, create webbing

Box tree moth caterpillar

Adult box tree moth

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On the Radar: Spotted Lanternfly▪ Invasive pest from Asia; introduced to US in 2014 ▪ Attacks a range of trees ▪ Eggs easily transported

Spotted Lanternfly AdultSpotted Lanternfly Egg Masses

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understanding and managing wisconsin’s most menacing

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