MAA NEWS MAA NEWS Fall2017_w-1 - Page 3

Winter Moth/Gypsy Moth (continued from page 1) Preliminary Aerial Survey Results 2017 Massachusetts Dept. of Conservation & Recreation Forest Health Program We hope that this overall reduction in winter moth populations in Massachusetts is due in part to Dr. Elkinton’s efforts towards the biological control of winter moth using Cyzenis albicans, a tachinid fly. The fly parasitizes the caterpillars specifically of winter moth. Dr. Elkinton remains cautiously optimistic at this time before cred- iting the parasitic fly with this widespread reduction in winter moth until his lab has gathered more information. C. albicans has been released across 41 sites in Massachusetts and has been estab- lished in at least 17 of those sites, as evidenced through the recov- ery of flies in winter moth in subsequent years. At one site in Wellesley, MA, these flies have been observed to be spreading from the initial release location, with their populations increasing along- side an observed decrease in the winter moth population there. The evidence is building and so far it is promising. GYPSY MOTH 2017 – Encouraging signs for the coming year Where winter moth giveth, gypsy moth taketh away. Lymantria dispar has been in Massachusetts since its introduction by an amateur entomologist in the late 1860’s into Medford, MA. The egg stage of this insect overwinters. 500-1000 eggs are laid in tan-brown, fuzzy masses on trunks and branches of trees, the sides of homes, lawn furniture, and other inanimate objects. Egg hatch can occur between the last week in April and the first week in May depending upon temperatures. In 2017, gypsy moth eggs were observed hatching on 4/26/17 in Belchertown, with many other locations reporting egg hatch just before or after that time. Egg hatch typically occurs when 90-100 GDD’s (base 50°F) have accumulated. Shortly thereafter, the tiny, newly emerged caterpillars crawl to the canopies of their hosts (certain oaks preferred but other hosts are too many to list) and disperse via ballooning. Caterpillars undergo changes in appear- ance as they age – maturing into hairy larvae with yellow/black mottled head capsules and bright rows of blue and red spots/warts. Pupation typically occurs by the third week in June, at which time caterpillars seek areas to become dark brown/red- dish pupae. Adults are seen by late June/early July, mate, and the females lay the eggs that will overwinter. Gypsy moth activity in 2017 was intense. Residents in Massachu- setts, particularly in southeastern central MA and the southeast- ern portions of Franklin, Hampshire, and Hampden counties, experienced high populations of this insect. Caterpillar frass (excrement) could be heard and felt raining down from tree canopies at various locations, covering patios and lawn furniture. This was no surprise, due to the large numbers of egg masses overwintered from the 2016 outbreak in these locations. What we had hoped, however, was that increased spring rainfall in 2017 (particularly as compared with drought conditions in 2015- 2016), would give rise to the gypsy moth killing fungus (Ento- mophaga maimaiga) and cause a caterpillar population collapse earlier than what in fact occurred this season. Instead, many caterpillars lived to older and larger instars and were thus capable of heavy feeding before succumbing to the fungus. Massachusetts went from experiencing over 352,000 acres of defoliation due to gypsy moth in 2016 to 922,460 acres of defoliation in 2017 as estimated by the MA Department of Conservation and Recreation. Around the week of 6/24/17, reports came flooding in from across the state of caterpillar mortality due to Entomophaga maimaiga. The Elkinton Lab reports that at the sites they were monitoring in Massachusetts, over 95% of their sampled caterpil- lars perished due to this fungus. Many locations had nearly 99% mortality, with the exception of a location monitored in Amherst, MA, which saw drastically lower mortality rates. The hope is, due to the high percentages of gypsy moth caterpillar death by the fungus, that most areas in Massachusetts will receive a break in 2018 from this insect. This may be particularly true for locations that experienced high populations of gypsy moth in 2016 and 2017, where the fungal reservoir has now been replenished. However, there are areas (such as the study site in Amherst) that experienced heavy gypsy moth populations for the first time in 2017 and had caterpillars that did not succumb to the fungus and successfully made it to adulthood. At those locations, egg masses are still locally prolific and may give rise to caterpillars in 2018. Therefore, we can breathe a sigh of relief that E. maimaiga did come to our rescue in 2017, although we may not see its full benefit until 2018. However, continue to keep your eyes open for egg masses. For more information about winter moth, gypsy moth, and other insect pests in Massachusetts, visit: ➜ https://ag.umass.edu/landscape Tawny Simisky is an Extension Entomologist at UMass Extension Landscape, Nursery, and Urban Forestry Program. Preliminary Aerial Survey Results 2017 map courtesy of the Massachusetts Department of Conservation and Recreation. MAA NEWS / Fall 3