Before a squirming blanket of caterpillars returns to Hanover sidewalks this spring, the Office of Facilities, Operations and Management is taking action with its first insecticide campaign. FO&M's plan of attack, however, is not focused on saving the soles of students' shoes, but on preserving the College's historic trees.
Campus arborist David DiBenedetto, who has been monitoring the egg masses in the trees as well as the actual caterpillar hatch, noticed the first eggs physically hatching in the last couple weeks. Last year, the caterpillar infestation was so widespread that one could scarcely take a step without squishing a bug.
In response, FO&M launched a large-scale spraying operation this week, which involves spraying trees with the organic pesticide Conserve SC from trucks using high pressure sprayers and portable backpack sprayers. The office will be targeting trees along East Wheelock Street in front of the Alumni Gymnasium tomorrow, as well as Massachusetts Row, Dartmouth Row, Tuck Mall and the Green itself, FO&M Director of Operations Frank Roberts said. Spraying will occur between 4 a.m. and 6 a.m. to minimize human contact, and FO&M has sent BlitzMail messages warning students in affected residential halls about the potential noise spraying might cause. Other areas of campus that need insecticide will be spot-treated with backpack sprayers.
After causing extensive defoliation last spring, the caterpillar population incited concern from FO&M. Roberts noted the maple trees on the south side of the Green as particularly devastated specimens, to the point that "the caterpillars pretty much ate the majority of the leaves off."
Roberts added that if caterpillars return in even greater numbers than last year, the risk is permanent damage to the trees from defoliation. He also warned that, if defoliated, weaker or older trees could die from the infestation.
Despite the large number of calls Roberts received regarding caterpillars on buildings and sidewalks last year, he emphasized that the concern for the trees is what motivates this year's insecticide drive.
"We are not spraying because caterpillars may be a nuisance to people," Roberts said. "It is the impact on the trees we are worried about."
Conserve SC is a natural pesticide made from soil bacteria with Spinosad, which directly targets forest tent caterpillars. After consulting with the University of New Hampshire Cooperative Extension, FO&M chose the pesticide not only for its effectiveness in targeting caterpillars, but also for the speed with which the insecticide dries and degrades.
According to the material data safety sheet for Conserve SC, the chemical "may cause slight eye irritation" with direct contact, but is generally not harmful to humans.
FO&M also discussed use of the insecticide with the Department of Pharmacology and Toxicology to ensure its safety.
The material data safety sheet does warn, however, that the "material is toxic to aquatic invertebrates and fish." In order to prevent harm to the aquatic ecosystem, FO&M is taking precautions such as not spraying in windy conditions to minimize drift of the pesticide. Most importantly for the fish, Roberts also said that Conserve SC is not being applied directly to water.
"We are very pleased with the way the two days of spraying have gone so far," Roberts said. "One, that we have been able to do it, and two, that there have been no problems with drift."
Results from the pesticide application are not immediate, Roberts said, but the product's website does promise evidence of control within one to three days. FO&M will continue monitoring trees after this week to ensure that the caterpillars are not damaging them, Roberts added.
Biology professor Matthew Ayres, who has studied the caterpillars extensively, supported the College's decision to use the pesticide, in spite of his excitement about the "interesting ecological phenomenon."
Population eruptions of the forest tent caterpillars come in three-year cycles, and the second year generally has a heavier population than the first year.Despite FO&M's attempts to control the caterpillar operation, Ayres assured the campus that they would still see these "unusual animals."
"There are going to be plenty of caterpillars for everyone to see," Ayres said.
