Efficacy and mode of action of kaolin and its interaction with bunch-zone leaf removal against Lobesia botrana on grapevines

Lobesia botrana control strategies in vineyards aim to develop environmentally safe tools as an alternative to synthetic insecticides. The activity of kaolin on L. botrana performance was studied in laboratory and field bioassays. The efficacy of kaolin and Bacillus thuringiensis (Bt) against the moth, with or without bunch-zone leaf removal (LR), was compared in four trials carried out in vineyards in north-eastern Italy. In the laboratory bioassays, kaolin berry coverage reduced the egg-laying preference of L. botrana by 53% and decreased female survival and fecundity by 22 and 82%, respectively. Kaolin egg coverage reduced the hatching rate by 14%. The larval settlement preference for berries covered with kaolin was reduced by 72%, but larval survival and development were not affected. In the field bioassay, kaolin reduced the egg-laying preference by 84%. In the field trials, kaolin, Bt and LR reduced L. botrana infestation significantly. Although Bt was more effective than kaolin, the efficacy of the two products was similar when combined with LR. Based on the results obtained and its effectiveness also against grapevine leafhoppers, kaolin can play an important role in the context of integrated pest management in vineyards.