Submitted to: National Research and Action Plan for Silver Leaf Whitefly
Publication Type: Abstract Only
Publication Acceptance Date: 2/18/1999
Publication Date: N/A
Technical Abstract: 'Green Glaze' collard segregates into glossy (GGG) and nonglossy (GGN) phenotypes. In small plots, GGG averaged significantly fewer whitefly adults and nymphs than did a standard, nonglossy cultivar or GGN. During 1997-98, we evaluated the effects of planting pattern on infestations of Bemisia argentifolii and the occurrence of natural parasitoid species. Overall, there were no differences in the abundance of whiteflies on GGG when it was planted in solid 20-plant plots or when it was alternated every other plant with GGN. However, in some cases, whiteflies on GGN were reduced in the mixed plots. Overall, GGN-Solid Planting (SP) had 52% of the whitefly adults, GGN-Mixed Planting (MP) had 38%, GGG-SP had 4%, and GGG-MP had 6%. In 1998, native parasitoid species were monitored with yellow sticky cards. Significantly higher numbers of parasitoids were collected in GGN-SP than in GGG-SP. Counts of parasitoids were intermediate in the mixed plots. An unrelated, normal-appearing F1 hybrid, 'Blue Max' (BM), also had significantly fewer whitefly adults, nymphs, and eggs than open-pollinated, susceptible cultivars. However, BM is not as resistant as the glossy collards, and its mechanism of resistance is not known. In 1998, BM and a susceptible collard cultivar, 'Morris Heading' (MH) were planted in a similar experiment. As with GGG, there was no difference in the resistance of BM in either planting scheme, but late in the season when whitefly populations were very large, the number of whiteflies on MH was reduced in the mixed plots. Overall, MH-SP had 46% of the whitefly adults, MH-MP had 34%, BM-SP had 10%, and BM-MP had 10%. Thus, planting pattern appears relatively unimportant in the deployment of these sources of resistance.