Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/1996
Publication Date: N/A
Interpretive Summary: The diamondback moth has become a major limiting pest in cabbage and other crucifer production in Florida and throughout the world. Resistance of diamondback moth to virtually all classes of insecticides has markedly increased the cost and risk of producing cabbage causing some Florida growers to drastically curtail or even abandon the production of cabbage. Scientists at the Insect Attractants, Behavior, and Basic Biology Research Laboratory, Gainesville, Florida, are developing alternative control tactics that can be used in IPM programs to manage diamondback moth with less reliance on conventional pesticides. Collard greens were strip-planted between two cabbage fields in spring 1995. The collards were almost totally destroyed by diamondback moth but cabbage plants on either side of the trap planting were virtually free of damage. Large numbers of parasites also were produced from diamondback larvae feeding on the collard greens. Planting collards in and around cabbage fields could serve as a 'trap' to concentrate diamondback moth populations which then could be sprayed selectively with pesticides if needed. Trap plantings of collar greens also could be used as 'insectaries' to maintain and increase populations of native and exotic parasites of diamondback moth. Incorporation of the 'trap crop' concept into IPM programs could reduce the number of sprays needed for control of diamondback moth in cabbage and slow the development of pesticide resistance.
Technical Abstract: Collard greens (Brassica oleracea var. acephala L.) were strip-planted between two cabbage fields in Bunnell, Flagler County, Florida in spring 1995. More larvae of the diamondback moth (DBM), Plutella xylostella (L.), were found on collard plants than on cabbage plants in the adjacent fields. The parasitism rate of DBM larvae collected from the collard plants reached 72% in early May and was higher than for larvae collected from the cabbage plants in adjacent fields. Parasitoids recovered from DBM larvae were mainly Diadegma insulare (Cresson). No spread of DBM from collard to the adjacent cabbage was found. The damage to collard plants caused by DBM larvae was greater than on cabbage plants. At harvest, the cabbage heads on the first row next to the collard planting showed less worm damage than did cabbage on the first row on the side of the field away from the collards. However, there was no significant difference in damage ratings of cabbage heads sampled near the middle of the field and damage to heads on rows nearest the collards. The results suggest that collard greens have potential as a trap crop of DBM in cabbage fields, and that collards can play an important role in maintenance of the natural enemy, D. insulare.