Influence of leaf trichome type and density on the host plant selection by the greenhouse whitefly, Trialeurodes vaporariorum (Hemiptera: Aleyrodidae)

Abstract

Host selection by the adult greenhouse whitefly Trialeurodes vaporariorum (Westwood) was assessed on two pelargonium plant cultivars, Pelargonium × domesticum Bailey (regal) and P. × hortorum Bailey (zonal), using Petri dish bioassay chambers in choice and no-choice tests. Plant characteristics which could influence the oviposition preference of the whitefly, i.e., type and density of trichomes on the abaxial leaf surface, was determined. A strong host preference was observed for the regal compared to the zonal pelargonium by the adult whiteflies. In no-choice tests, adults laid a significantly higher number of eggs on regal than on zonal leaves both at 24 and 48 h post-exposure, respectively. After exposure to the adult whitefly, the number of eggs in choice tests were similar between cultivars at 24 h, but were higher for regal at 48 and 72 h. The total number of trichomes (sng, straight non-glandular + sg, straight glandular) per 0.50 cm2 was significantly less on regal [mean (sng + sg) ± SE; 43.1 ± 1.5) than on zonal leaves (60.5 ± 1.2); however, the sng trichomes were significantly higher on the zonal (49.5 ± 1.2) than the regal leaves (28.6 ± 1.0). Also, the number of sg trichomes was slightly higher for the regal cultivar leaves compared to the zonal, being 14.4 ± 1.2 and 11.2 ± 0.5, respectively. Results suggest that the trichome density, type, and ability to express glandular exudates can affect adult whitefly Pelargonium cultivar preference and plays an important role in their host plant selection for oviposition.