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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University of Wisconsin–Madison Insect Diagnostic Lab
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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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University of Wisconsin–Madison Insect Diagnostic Lab
Map Sources: WI-DATCP
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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
EAB Chemical Controls
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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
Trending: Viburnum Leaf Beetle
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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
Trending: Lily Leaf Beetle
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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
LLB Damage▪ Both larvae and adults feed on foliage
Damage of small larvae
Severe damage
Holes in leaves
Adult Feeding15
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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
Trending: Gypsy Moth▪ Distinct uptick in gypsy moth numbers in 2020 ▪ DATCP: GM populations are “intermediate”
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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
Gypsy Moth Quarantines
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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
Japanese Beetle Damage
Significant Japanese beetle DamageFeeding on flowers
Skeletonization
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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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
Larvae36
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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
▪ 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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University of Wisconsin–Madison Insect Diagnostic Lab
▪ 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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University of Wisconsin–Madison Insect Diagnostic Lab
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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University of Wisconsin–Madison Insect Diagnostic Lab
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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