Km. Heinz et Fg. Zalom, PERFORMANCE OF THE PREDATOR DELPHASTUS-PUSILLUS ON BEMISIA RESISTANT AND SUSCEPTIBLE TOMATO LINES, Entomologia experimentalis et applicata, 81(3), 1996, pp. 345-352
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 te
sted 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 lifetim
e fecundities and walking speeds than beetles housed on Alta. No culti
var-specific differences were observed in D. pusillus longevities or h
andling times. Combining these observations with previously published
reports of reduced B. argentifolii population growth rates on Alta com
pared to VF145B7879, we tested the hypothesis that increased levels of
whitefly biological control could be obtained on VF145B7879 by compar
ison to Alta through releases of D. pusillus. Analyses of results obta
ined 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 beet
le residence times on Alta than on VF135B7879 may have compensated for
the significantly slower walking speeds and reduced lifetime fecundit
ies observed on Alta and produced a neutral effect of foliar trichome
densities on B. argentifolii biological control.