Effect of kaolin particle film on Thrips tabaci (Thysanoptera: Thripidae), oviposition, feeding and development on onions: A lab and field case study

Laboratory studies were conducted to evaluate the effects of a kaolin-based particle film on biological characteristics of the onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), on onions. Oviposition rate was significantly reduced on kaolin-treated vs. water-treated onion leaves and plants, in choice and no-choice assays. Hatch rate was reduced when kaolin particle film was applied over eggs on onion leaves. The time required for development of larval stages was significantly increased and mortality was significantly higher on kaolin than on water-treated onion leaves. Feeding choice was influenced by the presence of the kaolin treatment and in choice assays both larvae and adults fed significantly less on kaolin-treated than on water-treated leaves. In a field study, significantly more adults were captured in the beginning of the season on control than on kaolin-treated plots, and at population peaks significantly more larvae and adults were harbored in control plots. The results indicate the potential of kaolin particle film against onion thrips in an integrated pest management program. However, because of the importance of a continuous coverage of plant material with kaolin particle film, better application methods and perhaps frequent applications will be required to cover newly expanding foliage.