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United States Department of Agriculture

Agricultural Research Service

Title: Evaluation of Resistance to Whiteflies (Homoptera: Aleyrodidae) in Solid and Mixed Plantings of Collard

Authors
item Jackson, David
item Farnham, Mark
item Simmons, Alvin
item Van Giessen, W. -

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 7, 2000
Publication Date: N/A

Interpretive Summary: Whiteflies are a major pest of commercial collard crops. The development of whitefly-resistant collard cultivars is a promising approach for managing this pest. Fourteen collard entries were evaluated for resistance to naturally occurring populations of whiteflies at Charleston, SC, 1993-1995. Overall rankings of collard entries for resistance to whiteflies were consistent among years. Collards with glossy leaves were the most resistant entries in the field. However, in no-choice laboratory experiments, there were no differences in the growth rates of whitefly populations on glossy or non-glossy collard entries. This suggests that the resistance of glossy collard to whiteflies is due to a nonpreference mechanism. Over a 2-year period, there were no differences in the abundance of whiteflies on a glossy collard when it was planted in solid 20-plant plots or when it was alternated (every other plant) with a non-glossy collard. Higher numbers of native whitefly parasitoids were collected on yellow sticky cards in the solid plantings of a non-glossy collard than were collected in the solid plantings of a glossy collard. These data show that planting pattern of collard entries is relatively unimportant in the development of these sources of host plant resistance.

Technical Abstract: Fourteen collard entries were evaluated for resistance to whiteflies (primarily Bemisia argentifolii) at Charleston, SC, 1993-1995. Rankings of collard entries for resistance were consistent among years, and each season there was a significant correlation between counts of adults and counts of immatures. The glossy phenotype of 'Green Glaze' was one of the most resistant collards, whereas the non-glossy phenotype of 'Green Glaze' was very susceptible. Two other glossy collards and 2 normal-appearing F1 hybrid cultivars ('Blue Max' and 'Top Bunch') also had fewer whitefly adults, nymphs, and eggs than the open-pollinated cultivars. In no-choice experiments, there were no differences in the intrinsic rates of population growth (rs) for B. argentifolii on two glossy ('SC Glaze' and 'Green Glaze'-glossy) or two non-glossy collard entries ('Vates' and 'Blue Max'). Over a 2-year period, there were no differences in the abundance of whiteflies on the glossy phenotype of 'Green Glaze' when it was planted in solid 20-plant plots or when it was alternated every other plant with the non-glossy phenotype. However, sometimes the number of whiteflies on the non-glossy phenotype in mixed plots was reduced. There also was no difference in the abundance of whiteflies on the resistant collard 'Blue Max' when it was planted in solid plots or when it was in mixed plantings with the susceptible collard 'Morris Heading.' Higher numbers of native whitefly parasitoids (primarily Eretmocerus spp.) were collected on yellow sticky cards in the solid plantings of the non-glossy phenotype of 'Green Glaze' than were collected in the solid plantings of the glossy 'Green Glaze' phenotype. Counts of parasitoids on sticky cards in the mixed plots were intermediate.

Last Modified: 4/20/2014
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