Host preference and performance of Bemisia argentifolii (Homoptera: Aleyrodidae) on weeds in central Italy

Several herbaceous weed species of the Mediterranean flora found around cultivated greenhouses of central Italy were used in a comparative study of the developmental rate of Bemisia argentifolii (Bellows and Perring). The relative importance of various weed hosts in local population dynamics of the whitefly was investigated using a choice test and the construction of age specific life tables. Among the 18 weed species studied, 11 were readily accepted in the choice test. After 72 h, the whiteflies clearly showed a preference for 2 species--Sonchus oleraceous L. and Solanum nigrum L.--on which nearly 53% of the released whiteflies were found. Approximately 90% of the remaining population preferred Conyza canadensis L. (Cronq.), Euphorbia elioscopia L., E. peplus L., and spontaneous clover Trifolium repens L. Only a very low number of insects (approximately 4.5% of the total) were recorded on the remaining weeds--Ricinus communis L., Euphorbia characias L., Euphorbia maculata L., Euphorbia dendroides L. Ranking of host plant quality determined by the life table statistics coincided with the ranking of host preference assessed by the choice test. The intrinsic growth rate for whiteflies varied from 0.11 on S. oleraceous to 0.004 of Euphorbia dendroides. These experiments demonstrated that in the absence of cultivated host plants such as tomato, squash, or the ornamental plant poinsettia, the whitefly B. argentifolii may find suitable hosts where it can complete its development