What happened to the gypsy moth epidemics in the Northeast US?
It appears that the gypsy moths were controlled by pesticide spraying by the US Forestry Service. 

The defoliation areas measured peaked at 12 million acres in 1981 and again at 7 million acres in 1990. 



In response, there was significant spraying of various insecticides starting from 1982 through 1996, peaking in 1990. This spraying managed to keep gypsy moth defoliation areas under 2 million acres since 1993.