Side effects of kaolin on natural enemies found on olive crops
Abstract: Protected barriers of kaolin, a natural clay mineral, were tested against olive pests inthe last few years with good results on Bactrocera oleae, the most serious pest of olive groves.Good control of the carpophagous generation of Prays oleae, as well as a minor presence ofSaissetia oleae, were also reported.Adults of Psyttalia concolor (parasitoid of B. oleae), Chrysoperla carnea (oophagous predator ofP. oleae), Chilocorus nigritus (predator of diaspidid scales) used in this work as representative ofChilocorus bipustulatus and Anthocoris nemoralis (predator of Euphyllura olivina and Liothripsoleae) were selected to be exposed to an inert surface treated with kaolin at the maximum fieldrate used against B. oleae. Dimethoate was used as reference compound. Mortality was recordedat 24, 48 and 72 h. Sublethal effects, as life span in C. nigritus and reproductive parameters(fecundity and fertility in case of C. carnea and A. nemoralis, beneficial capacity in P. concolor)were also assessed.Kaolin was classified as harmless (1) to adults of C. nigritus. There were no effects on mortalityon C. carnea and P. concolor, although C. carnea fecundity and P. concolor progeny wereslightly reduced (2). A. nemoralis was the most sensitive of the four insect tested, with 44%mortality and 66.6% reduction of eggs production. Dimethoate was very toxic with 100%mortality for each test species after only 24h of exposure. Compared to classical insecticidecommonly used in olive crops as dimethoate, Kaolin seems to be a promising compound becauseof its selectivity. However, because of its uncommon mode of action, other modes of exposurethan contact with a treated surface need to be tested to confirm or infirm the apparentharmlessness of this product.