Augmentative releases of the predatory mite Kampimodromus aberrans in organic and conventional apple orchards

Experimental releases of the predatory mite Kampimodromus aberrans (Oudemans) were conducted in organic and conventional apple (Malus domestica Borkh.) orchards located in North-eastern Italy. The most frequent insecticides used in organic orchards were pyrethrins and spinosad, whereas neonicotinoids, organophosphates and insect growth regulators were mostly used in conventional orchards. K. aberrans population levels were significantly higher in release plots as compared to control plots and K. aberrans populations were higher in organic compared to conventional orchards. In conventional orchards, K. aberrans released in 2010 and 2011 did not establish probably because of a series of non-selective insecticide and fungicide treatments. In one experimental site, releases were evaluated in two organic orchards, one of Florina cv. and the other of Golden Delicious cv., managed with the same cropping systems. On Florina, K. aberrans population appeared to be larger than on Golden Delicious suggesting a potential role of leaf morphology in predatory mite colonization. On Golden Delicious, A. andersoni population densities were lower in release than in control plots. Implications for mite management in organic and conventional orchards are discussed.