EVIDENCE OF PREIMAGINAL OVERWINTERING OF DIAMONDBACK MOTH, PLUTELLA-XYLOSTELLA (LEPIDOPTERA, PLUTELLIDAE) IN MICHIGAN

We investigated the possibility of overwintering of the diamondback mo th, Plutella xylostella L., in central Michigan. In the spring of 1993 , counts of immature stages on brassicaceous weeds in a field previous ly planted to broccoli revealed a small but significant number of late instars that could not be attributed to oviposition of immigrant moth s from the southern United States. We suggest that crop debris and sno w cover played an important role in sheltering the larvae, which are k nown to tolerate sub-freezing temperatures. There was no indication of adult survival.