Performance of the predator Delphastus pusillus on Bemisia resistant and susceptible tomato lines
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Host plant resistance and biological control are often assumed to act additively to suppress populations of agricultural pests. Using tomato trichome based resistance to the whitefly Bemisia argentifolii, we tested this additivity assumption with Delphastus pusillus, a coccinelid predator of Bemisia. Various life history traits of D. pusillus were measured on the tomato cultivar 'Alta,' which possessed foliage with 3-fold greater trichome densities than the second cultivar 'VF145B7879.' Beetles housed on VF145B7879 exhibited significantly greater lifetime fecundities and walking speeds than beetles housed on Alta. No cultivar-specific differences were observed in D. pusillus longevities or handling times. Combining these observations with previously published reports of reduced B. argentifolii population growth rates on Alta compared to VF145B7879, we tested the hypothesis that increased levels of whitefly biological control could be obtained on VF145B7879 by comparison to Alta through releases of D. pusillus. Analyses of results obtained from replicated population trials detected significant reductions in whitefly populations due to D. pusillus releases, but they did not detect a significant influence of tomato cultivar on the ability of D. pusillus to suppress whitefly populations. Significantly longer beetle residence times on Alta than on VF145B7879 may have compensated for the significantly slower walking speeds and reduced lifetime fecundities observed on Alta and produced a neutral effect of foliar trichome densities on B. argentifolii biological control.
