Gypsy moth caterpillars have taken a serious bite out of the forests of New England this summer – in fact, their destruction is so severe, it is visible from space.
Aerial photos taken May 25 and June 26 from the NASA’s Aqua and Terra satellites show just how much defoliation these furry caterpillars caused in just one month’s time.
The healthy forests appear green in these satellite images, whereas the gray-brown tinted regions are the parts of the forest that have been munched on by these hungry critters.
The beginning of summer is usually the worst time for forest defoliation, because caterpillars hatch in late April to early May and they voraciously eat leaves throughout the month of June, targeting the trees before they have had the time to regrow leaves.
Dry weather only makes problems worse, because dryness actually weakens the pathogens that usually harm the caterpillars. In addition, there has also been a decline in the caterpillars’ predator – the white-footed mouse – allowing the caterpillars to thrive unchecked.
Paul Ricard, Rhode Island’s forest health program coordinator of the Department of Environmental Management, told NASA that the outbreak is linked to two consecutive dry springs. However, he added, that he is not yet worried about the overall health of the forest because usually these trees can usually undergo a couple of seasons of heavy defoliation without huge turmoil.
However, the Providence Journal reports that eggs left behind by this year’s gypsy moth caterpillars could bring another severe infestation next spring as well.
According to the University of Illinois-Extension, gypsy moth eggs are laid and attached to the trees themselves. When they hatch in late spring, the caterpillars that emerge can be identified by 5 pairs of blue dots and 6 pairs of red dots on their backs. These caterpillars are also covered in a brown-gray fur. They avoid coniferous trees (firs and pines) and target deciduous trees (such as oaks) that make up most of New England’s hardwood forests.
Usually, young caterpillars feed during the day and older caterpillars feed at night. But during population booms like the one that has occurred this summer, they all eat whenever they get the chance.
Gypsy caterpillars aren’t the only tree-killing creatures. According to a 2001 study in BioScience, insects and disease combined to ravage about 45% more forest area each year than did wildfires. Still, the United States Department of Agriculture lists the gypsy moth as one of the worst offenders in killing trees because it has the largest role in defoliating hardwood trees in the eastern United States.
The trouble comes when a period of continuous destruction occurs. After a sustained attack, tree tops can become thin, buds and branches die, and parasites that attack stressed trees start to become more prevalent. This can then lead to huge die-offs in the forest.
With the large numbers of eggs left in the forests, populations of these caterpillars won’t start to decrease until well into the feeding period next season. But, there is some hope as area-wide outbreaks usually only remain high for around 3 years, so the forests should hopefully be in better shape by the summer of 2018.