Gypsy Caterpillars Gone Wild

Asked June 30, 2020, 2:50 PM EDT

Hello, How / Who can I report a Gypsy Caterpillar hot spot to in Rose Township Michigan? It sounded like rain. Even the pine trees were covered with them 6/26/30. They ranged in size from 1/2 inch to 2 inches. Our neighbor said he lost 50% of his trees. I've never seen them this bad. How can we stop the spread for next year?? Any advice will be greatly appreciated. Thank you!

Ogemaw County Michigan

1 Response

These are gypsy moth and their outbreak is tied to drought in last year. They are always with us each year but their numbers are kept in check when there is consistent rainfall to spread a fungus called Entomophaga. Outbreaks occur across the state each year depending on rainfall patterns. Gypsy moth can cause defoliation but rarely kill hardwoods like oak and poplar. These tree will put out a second set of leaves later in season. If an outbreak is large enough it can strip trees bare. At this point it is just about done for the season. If your neighbor has hardwoods like oak they likely will come back though it does put stress on the trees. Valuable trees that have to put out new leaves should be watered if conditions are dry to help the buds develop and eventually leaves open up. Pines are a more serious problem since they cannot put out new leaves if totally stripped. Populations will vary from year to year and the two major reasons are the fungus which will crash the population when rainfall occurs in May and June. The other reason is a virus attacks when populations get very large. In the last few years populations have soared and crashed in Macomb, Washtenaw, Kent, Van Buren and many other communities. A few locations developed their own private aerial spray program in early spring going after hatching caterpillars with a bacteria called Bt. A common pathogen used in gardens to kill caterpillars that feed on vegetables. Most sites have allowed nature to swing back the other way and crash the population which happens when we get normal rainfall in the spring. Some local residents will hire pesticide applicators to spray smaller properties. A five acre woodlot in a park was 100% stripped of foliage in 2007, south of Howell, Michigan and the next season rainfall allowed the Entomophaga to develop killing most of the caterpillars and that park has not seen an outbreak since that year. Private aerial spray programs can be setup by local communities. The State and most counties have not coordinated spray programs since the late 90's. I would contact your local township to get their feedback on this issue. The Michigan Department of Agriculture and Rural Development maintains a list of Pesticide applicators that includes aerial applicators "AE" See the following list: https://www.michigan.gov/documents/mdard/2020_Pesticide_Application_Business_License_List_by_County_680870_7.pdf
For more information on gypsy moth and what residents can do to remove eggs and protect valuable tree see the following: https://www.canr.msu.edu/ipm/invasive_species/Gypsy-Moth/gypsy-moth-around-home