Tree Location and Winter Temperature Influence on Mimosa Webworm Populations in a Northern Urban Environment

Abstract

Mimosa webworm, Homadaula anisocentra Meyrick (Lepidoptera: Plutellidae) exhibits dramatic fluctuations in population levels on ornamental honeylocust, Gleditsia triacanthos L, in northern urban settings. Winter temperatures and tree location were evaluated for their effects on overwintering pupal survivorship and defoliation. Extremely cold winters caused high pupal mortality and were followed by low first-generation defoliation; an extremely mild winter caused low pupal mortality and was followed by very high first-generation defoliation. Pupal overwintering sites on heated structures were 5 to 9°C (3 to 5°C) above the ambient low temperatures, decreasing the probability of pupal exposure to lethal temperatures. Second-generation larvae moved 50 to 80 ft. (ca. 25 m) from infested trees to overwintering sites.