gypsy moth in michigan - newaygocountymi.gov
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Gypsy Moth in MichiganLymantria dispar dispar
October 9, 2021
Julie CrickNatural Resources
EducatorMSU Extension
Cheryl NelsonForest Health Forester
Michigan [email protected]
Mark ShermakSilviculturist
Forest [email protected]
Rod DenningDistrict Forester
Oceana, Muskegon and Newaygo Counties
Gypsy Moth (Lymantria dispar dispar)
1869 – Accidental release in Massachusetts.
1954 - First observation in Michigan.
• Population buildup in the late 1980’s led to large outbreaks in the early-mid 1990’s.
• Today GM is naturalized throughout Michigan- populations are moderated by predators, parasitoids, fungi (EM), and a virus (NPV).
• Entomophaga maimaiga fungus released in Michigan in 1991.
• General Population Dynamics-2-4 year outbreaks, 7 to 10 years of unnoticeable levels.
• Approximately 950,000 acres were defoliated in 2020.
Gypsy Moth in Michigan
HardwoodsPreferred:
*Oaks drive Gypsy Moth outbreaks*
Also feed on: aspen, apple, basswood (linden), birch, and
willow
Some species like red maple and ash, are not suitable hosts
for gypsy moth unless outbreaks are severe
ConifersIt is uncommon to see feeding
on conifers however:
Conifers such as white pine or spruce may be fed on later in
the year if other highly preferred species are not
available OR if outbreaks are severe
As the larvae grow, their list of host trees expands
Egg masses laid in July - Fall
Egg Masses in Fall
June/July at their 5 or 6th Instar
Hatch in May
Caterpillars
• Males have 5 instars
• Females have 6 instars
• Will feed for 6-8 weeks
Caterpillars – May to July• Small to large (1/4 inch to >2” long)
• Pairs of red and blue dots
• Hairy
• Frass staining siding/concrete
Movement of Caterpillars
• Crawling
• “Ballooning” – dangling from a thread of silk and blown by the wind
• Most caterpillars feed on trees less than 100-150 yards from where they
hatched
• Small caterpillars feed during the day
• Larger sizes feed at night and move down the tree to hide in bark or leaf
litter during the day
Pupal/Cocoon Stage• Late June – July• Found all over trees,
houses, trailers, etc.
Adult Moths
Begin to appear around the
beginning of July depending on
location
Females *do not*
fly
Eggs / Masses
- Protected by brown fuzzy material (fine hairs
from the body of the female)
- Hatching begins in early to mid-May in
southern part of MI and moves north
Egg Masses
Old egg mass
• August through winter
• Tan/brown and look soft and fluffy
• Old egg masses lose their color, fade to white, and have small pin size holes where caterpillars hatched
New egg mass
Nucleopolyhedrosis virus (NPV)
Naturally occurring virus specific to gypsy
moths
Entomophaga maimaiga
Introduced fungal pathogen that’s
statewide
Biological Controls
Nucleopolyhedrosis virus (NPV)
• Always in the population• Activates during
outbreaks
Entomophaga maimaiga
• Lives in soil –needs moisture to spread spores
Specific to Gypsy Moths
Biological Controls
Biological Controls
From Newaygo County, MI 10/05/2021
Parasitic Wasps• Parasitize eggs
• Very little to no impact to healthy trees/forests due to defoliation
• Trees will re-leaf in July/August
• Healthy trees can withstand multiple years of heavy defoliation before showing decline
• Some mortality is natural and thins forest canopies by removing stressed or dying trees and making way for healthier younger regeneration to take its place; a benefit to both the forest and wildlife
• Landscape/Yard trees may be more susceptible to defoliation if they were recently planted or are very old
• Oak decline is a combination of stressors:
• Nutrient poor, dry, sandy soils
• Older aged trees• Severe drought OR too
much rain• Frost, ice, wind damage• Armillaria root rot fungus• Two-lined chestnut borer• Long-horned beetles
• Trees slowly die over years
• Defoliation is a minor tree stressor and rarely contributes to oak decline whereas oak decline and mortality are driven by more severe tree stressors like drought, heavy rain, armillaria and two-lined chestnut borer
* Gypsy Moths do not transfer the oak wilt fungus *
• Typically, only defoliated during heavy outbreaks
• Trees take longer to recover from defoliation
• Heavy defoliation in one season can cause tree decline/mortality
• Look on trees, buildings, outdoor furniture and playsets - anything that's outside.
• Use a scraper or hard plastic card to scrape egg masses into a container of soapy water.
• Let them soak overnight, then bag and dispose of them.
• Alternately, egg masses can be placed in a fire and burned (snap, crackle, pop is delightful)
• Note that just scraping them onto the ground will not kill the eggs, and egg masses will still hatch next spring.
Residential Egg Mass Treatment –Individual Yard Trees
• Thoroughly soak each egg mass to prevent hatching next spring• Use when temps are above 45 degrees• Spot test oil-based solutions on vinyl and infrastructure surfaces
• Commercially available horticultural oils labeled for gypsy moth egg masses• Golden Pest Spray Oil (mostly soybean oil)• Neem Oil (vegetable oil from fruits and seeds from neem tree)
• Homemade solution of oil and water and dish soap• 1 cup vegetable oil + 1 cup water + 1 Tbs of dish soap
Residential Egg Mass Treatment –Individual Yard Trees
Image Credit: Conrad Gregoire and David Overholt, White Lake Property Owners Association, Ontario, Canada
Residential Caterpillar Control –Individual Yard Trees
• The use of systemic insecticides is NOT recommended due to their effect on non-target terrestrial and aquatic insects.
• Burlap barrier bands can be wrapped around a tree trunk.• Caterpillars hide under the flap of
burlap during the day• Knock caterpillars into a bucket of
soapy water to kill them• Pupal cases and egg masses may
also accumulate under burlap• Duct tape wrapped around a tree trunk
• 3 overlapping bands• Sticky side down• Small amount of petroleum jelly on
middle band
Image credit: Meadowood Tree Servicehttps://onnurserycrops.com/2020/06/29/the-monday-report-june-29th/
Residential Caterpillar Control –Individual Yard Trees
• Spray containing BTK (Bacillus thuringiensis var. Kurstaki); a naturally occurring bacteria in the soil that must be ingested by the caterpillar• Ground based foliar application• High powered sprayer • Ensure proper application rates
• Droplets must be small to be effective• Can repeat application• Effective through middle of third instar
phase• Avoid spraying trunk and bark directly –
could cause damage• The label is the law.
Image credit: https://www.sprayerdepot.com/blogs/sprayer-depot/how-to-overcome-the-challenges-of-tall-tree-spraying
Residential Caterpillar Control –Neighborhoods
(not uninhabited forest lands)
• Spray containing BTK (Bacillus thuringiensis var. Kurstaki); a naturally occurring bacteria in the soil that must be ingested by the caterpillar• Aerial application• Egg mass survey recommended• Follow instructions from applicator• Landowner notification required• Timing is critical
• Caterpillar age• Weather
• Regulated through MDARD = Michigan Department of Agriculture and Rural Development
Forested Lands
• No need to spray
• Mortality will be rare
• Some mortality is natural • Thins forest canopies • Removes stressed or dying
trees • Creates space for healthier
younger trees to grow
• Karner blue butterfly-Within Newaygo County
• Mitchel’s satyr butterfly
• Poweshiek skipperling
• Examples of Btk product label language, product labels differ.1. Aerial application- “This product must not be applied aerially within
¼ mile of any habitats of threatened or endangered Lepidoptera.”2. Non-Aerial application- “No manual application can be made within
300 feet of any threatened or endangered Lepidoptera.”
• Endangered Species Act of 1973. Protect the species and the ecosystems upon which they depend. Administered by the United States Fish and Wildlife Service.
• ESA prohibits “take” which refers to any activity that would harass, harm (which includes significant habitat modification or degradation), wound, kill, or the attempt to engage in such conduct.
• Pesticide labels are regulated by the Environmental Protection Agency. “It is a violation of Federal law to use this product in a manner inconsistent with it’s labeling.”
• Regardless of what information a pesticide label provides, applicators are required to comply with the ESA and any other applicable state or federal law.
Chris Mensing, Fish and Wildlife BiologistU.S. Fish and Wildlife ServiceMichigan Ecological Services Field Office2651 Coolidge Road, Suite 101East Lansing, MI 48823517-351-8316 (office)517-351-1443 (fax)[email protected]
Heather Keough, PHD District Wildlife BiologistU.S. Forest ServiceBaldwin/White Cloud Ranger District650 N Michigan AvePO Box Drawer DBaldwin, MI 49304231-745-5831 (office)231-745-2345 (fax)[email protected]
• 2010• Last severe outbreak • Over a half million acres were
defoliated
• 2019• Start of the current outbreak• 250,000 acres affected
• 2020• 950,000 acres
• 2021• > 1 million acres
• 2020 and 2021 - Dry conditions and late frost damage to oaks across the state compounded the rapid increase in defoliation
Like historical patterns, much of the area defoliated in northeastern Michigan in 2020 collapsed in 2021.
We have already seen large pockets collapse, roughly 200,000 acres from 2020 to 2021.
If we follow historical trends, much of the defoliation will collapse and somewhat more localized outbreaks will occur in 2022.
Good News! Site visits on Tuesday 10/5 to look at heavily defoliated areas from 2019 and 2020
Photos courtesy of Rod Denning, FAP Forester, Newaygo Conservation District
Site visits on Tuesday 10/5 to look at heavily defoliated areas from 2019 and 2020
Red Circles = NPV
Yellow Circles = Entomophaga
Parasitic Wasp
Photos courtesy of Rod Denning, FAP Forester, Newaygo Conservation District
Julie CrickNatural Resources
EducatorMSU Extension
Cheryl NelsonForest Health Forester
Michigan [email protected]
Mark ShermakSilviculturist
Forest [email protected]
Rod DenningDistrict Forester
Oceana, Muskegon and Newaygo Counties
Gypsy Moth in MichiganLymantria dispar dispar
October 9, 2021