Grounds Maintenance.keyUnderstanding and Managing Wisconsin’s Most Menacing
Landscape Insect Pests of 2020
PJ Liesch UW-Insect Diagnostic Lab
Twitter: @WiBugGuy pliesch@wisc.edu
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
quarantine; shifting efforts to biological control
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EAB Chemical Controls
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
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
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
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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Trending: Lily Leaf Beetle
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
LLB Damage Both larvae and adults feed on foliage
Damage of small larvae
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
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
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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Recent Trends:
Mild winter 2019-20 (decreased egg mortality)
Drier conditions in 2020 (decreased Entomophaga)
What to expect in 2021…???
Polar vortex impacts
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Gypsy Moth Quarantines
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
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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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
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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Trends in Wisconsin
Gaining footholds in northern WI
Populations highly variable in 2020
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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
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
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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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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
Pathogen: Milky Spore Disease
Photo Credit: Marie-Lan Nguyen via Wikipedia
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Chemical Controls
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
Conventional Organic
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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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
Larvae 36
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
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
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 
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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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
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)
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
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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
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 Adult Spotted Lanternfly Egg Masses
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