Gypsy Moth Problems?

MAA Past President Scott McPhee, MCA, of Harrison McPhee in Millis, MA offered some advice about Gypsy Moth Caterpillars.  Scott appeared on Fox News discussing the topic on June 14, 2017 - click here.

"The caterpillar feeding was delayed from all of the cool and wet weather. Now that it is hot, the caterpillar's are making up for lost time. We predict they will feed for another week or two because they are still in various stages of development.  Some are almost full size and others are half size and will need to eat for a few more weeks. The jury is out whether this wet spring will increase the chance of the fungal infection that will help to lower the population of the gypsy moth caterpillars. 

I would strongly suggest people call a certified arborist to evaluate the trees and to help put together a plan to combat the stresses that have been caused by varying amounts of defoliation on their valuable trees.  Successive years of defoliation can kill mature trees. Combine that with last year's terrible drought and many trees may decline and or die in this area."  (6/19/17)

The latest Gypsy Moth information can be found here in the UMass Landscape message from June 23rd, under Woody/Ornamentals - Insects.

Excerpt from UMass Extension's Landscape Message 6/16/17

Lymantria dispar caterpillars are in various sizes or developmental stages (instars) depending upon the location in Massachusetts. However, observations indicate that in many locations, these larvae are mostly in the 4th instar stage, however some 5th instars have been spotted. Male gypsy moth caterpillars go through 5 instars and female gypsy moth caterpillars have 6 instars. These caterpillars will continue to feed for the next couple of weeks, until they pupate, typically at the end of June. Male caterpillars will pupate just prior to the female caterpillars; pupation, like the transformation between the previous stages, does not happen all at once.

At this time and until the end of June, the defoliation they cause will be most noticeable. Reports made on 6/6/17 indicate that tree canopy thinning and complete defoliation were observed along I-90, approximately 4 miles east of Palmer, MA. On 6/15/17, a “55-65 MPH Survey” (driving along the MA Pike, I-90, on the way to a previously scheduled training) was conducted from the Westfield Exit (#3) to Exit 14 toward 95 south. Gypsy moth defoliation was highly visible beginning in Wilbraham while headed east through Palmer. On either side of the MA Pike, partial or complete defoliation (mostly oaks) could be seen. At mile marker 66.5 (just before) when headed downhill in the eastbound direction over the Quaboag River, there is a certain vantage point where you are at a higher elevation than the surrounding hillsides on either side of the highway. From that point of view, the defoliation was incredible. Large swaths on either side of the surrounding hills were covered in bare trees. When continuing east down I-90, the defoliation on either side of the highway continues through Sturbridge and roughly to the Charlton Plaza. From that point on, the defoliation was significantly less, at least on the trees visible from the highway. This trend continued roughly through Worcester, with any defoliation remaining in patches and certainly not to the extent of what was seen west of there. It seemed to not pick up again until roughly mile marker 98 and then was sporadic and relatively light (again, when thinking about the previously described areas) until you reach Hopkinton and Exit 11A to 495. Defoliation in that area seemed again analogous to what was seen from Wilbraham to the Charlton plaza. By mile marker 108.7, defoliation dropped to sporadic, light patches again. This limited, quick survey ended at Exit 14 and no samples of caterpillars were taken at that time due to safety concerns and time limits. However, it will be interesting to see what the 2017 aerial survey maps from the MA Department of Conservation and Recreation look like for defoliation this year.

Caterpillars are actively crawling up and down tree trunks, a behavior which makes them more likely to be exposed to pathogens, including the fungus, Entomophaga maimaiga. Reports of the sound of frass (excrement) dropping from the canopy where these caterpillars are feeding have been made. (The sound of frass dropping could be heard in Belchertown on 6/9/17 and Hanson on 6/15/17.) Roughly, 1- 1.5-inch long gypsy moth caterpillars have been observed resting or crawling on tree trunks and branches in Amherst as of 6/14/17. These caterpillars are dark in color, hairy, and the “warts” have developed to include the characteristic blue and red coloration, along with a head capsule that is yellow and mottled with black markings. In areas where gypsy moth caterpillars are abundant, citizens are dealing with caterpillars crawling all over the sides of homes, sheds, lawn furniture, and dropping from these locations and nearby trees. Caterpillars may be found on driveways, along with shredded sections of leaves due to their feeding, which are easily visible against that background. In Amherst on 6/12/17, caterpillars were found in a cluster, hidden behind a sign that was leaned up against a Norway maple. The sign was moved from the shaded area beneath the tree to a location in full sun, in order to inspect the cluster of caterpillars on the tree. In moments, the sun heated the sign and 50+ caterpillars came crawling down from where they were hidden along the edges of said sign. See the Regional Reports above for more information about gypsy moth activity.

According to prior reports from the Elkinton Lab, successful infection of gypsy moth caterpillars with the insect-killing fungus Entomophaga maimaiga, has begun. It is important to note that even with fungal infection in the caterpillars, we may still see significant defoliation in certain areas of Massachusetts this year due to this insect. Dr. Joseph Elkinton and his lab group, along with other local cooperators, are conducting a study that he is referring to as the “Cloud of Death Experiment”! What Dr. Elkinton means by this is that the research will aim to detect the amount of air-borne spores of the Entomophaga maimaiga fungus in certain locations of Massachusetts throughout the rest of the 2017 caterpillar activity (roughly through June). He and his lab hope to compare this to a measurement of the caterpillars killed at these various locations while determining if the fungus (or virus) is responsible. The Elkinton Lab has sites in Amherst, Belchertown, Brewster, Eastham, Hanson, and West Bridgewater to conduct these observations. To date, they have reported fungal activity at some of these sites, now with approximately 30% mortality due to Entomophaga maimaiga observed in caterpillars being reared on artificial diets (in the lab) collected from these sites. Anecdotally in the field, however, some reports of gypsy moth caterpillars “disappearing in large numbers” have been made at various locations across the state. This may be, in part, due to the behavior change that occurs when caterpillars reach the 4th instar. If an observer is used to seeing the caterpillars actively feeding on foliage during the day, they may be surprised to find them missing. The 4th instar caterpillars will change their behavior such that they feed at night, while hiding during the day. That being said, in high populations, even 4th instar caterpillars will feed at any time, daytime included. Fungal spores were isolated from a caterpillar collected from Belchertown on 6/9/17; however, the majority of the (many) caterpillars observed on that date were healthy and actively feeding (even during the day) at that location. Reports of caterpillar dieback at a location in Marlborough were also made on 6/15/17. The Elkinton Lab expects the percentage of caterpillars killed by the fungus will increase, but unfortunately, we cannot determine at this time how large of an impact the fungus will have on gypsy moth this year. Look to the Landscape Message for continued updates about Dr. Elkinton’s research as well as reports concerning the activity of Entomophaga maimaiga in Massachusetts.

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