In Switzerland, natural pyrethrins are currently the only registered insecticide to control the leafhopper Scaphoideus titanus, the main vector of grapevine Flavescence dorée, in commercial vineyards. In order to find alternative products against this insect, we tested the effectiveness of kaolin, a white inert aluminosilicate mineral, in 11 independent field trials over four consecutive years from 2018 to 2021. The use of kaolin at rates between 20 and 40 kg/ha applied two to three times at the beginning of hatching resulted in an average reduction in leafhopper densities of 36.8 % with efficacy values ranging from 0 to 88.9 % for the 18 different interventions. Overall, the efficacy of the different kaolin dosages and application strategies did not equal those commonly recorded for natural pyrethrins, which showed a mean efficacy of 74.8 % in 6 independent field trials with reduction values ranging from 41.3 to 97.4 %. In view of the highly variable efficacy levels of kaolin observed in our assays, we conclude that the use of kaolin to control S. titanus in Swiss vineyards does not provide an efficient alternative to natural pyrethrins in compulsory control areas.
