ARS | Publication request: EFFECT OF HABITAT TYPES ON POPULATION DENSITIES AND PARASITISM OF DIAMONDBACK MOTH (LEPIDOPTERA: PLUTELLIDAE) LARVAE IN CABBAGE FIELDS

Submitted to: Journal of Entomological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 29, 1996
Publication Date: N/A

Interpretive Summary: The diamondback moth is the most destructive pest of cabbage and other cruciferous crops around the world. Over the past 10 years, the diamondback moth has become such a severe problem in Florida that it threatens the continued existence of Florida's $30 million fresh market and transplant cabbage industry. Scientists at the Insect Attractants, Behavior, and Basic Biology Research Laboratory, Gainesville, Florida, are investigating ways to manage the diamondback moth problem with less reliance upon conventional pesticides. Systematic examinations of cabbage plants in commercial cabbage fields showed that diamondback moth larvae were more abundant at the ends of fields adjacent to weed-filled drainage ditches than at field ends abutting wooded swamp areas. Diamondback moth populations increase in numbers around the edges of fields, and then spread into the interior. To overcome the edge effect, control measures can be targeted along field margins resulting in fewer pesticide applications that blanket the entire field. In addition, the field edges can be used as incubation sites for parasitoids that attack diamondback larvae. Combining the tactics of targeted spraying and parasitoid releases should be less costly to the grower, provide less opportunity for the development of pesticide resistance in diamondback moth, and reduce reliance upon highly toxic pesticides.

Technical Abstract: Systematic examinations of cabbage plants in five fields near Bunnell, Flagler County, Florida, in spring 1995 showed that diamondback moth (DBM), Plutella xylostella (L.), larvae were more abundant at the ends of fields adjacent to weed-filled drainage ditches than at field ends abutting wooded swamp areas. There were no significant differences in the numbers of DBM larvae on cabbage plants on the edge of fields next to other cabbage fields or at sites located towards the interior of the fields. Three of five fields sampled showed a spread of DBM from the ends next to drainage ditches inward up to 1/4 length of the fields. Cabbage heads rated for damage by DBM larvae at harvest showed a distributional pattern similar to that observed for DBM larvae. Parasitism of DBM larvae was not significantly different between row ends and interior sites. These results suggest that DBM first invaded cabbage fields from outside areas, and that more DBM spread to the interior of the fields from adjacent open, weed-filled ditches than from bordering wooded and bushy areas.