Control of Trialeurodes vaporariorum (Westwood) adults on glasshouse-grown cucumbers in four different growth substrates: an efficacy comparison of foliar application of Steinernema feltiae (Filipjev) and spraying with thiamethoxamn

Authors: ZIGA LAZNIK, DRAGAN ZNIDARCIC, STANISLAV TRDAN

Abstract: In a glasshouse experiment, the effectiveness of the entomopathogenic nematode (EPN) Steinernema feltiae (Filipjev) (Rhabditida: Steinernematidae) was compared with thiamethoxam for the control of adults of the greenhouse whitefly (GWF), Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae), on slicer cucumbers. In a period from mid June to the end of August (2007 and 2008), cucumbers were grown in 4 different growth substrates: expanded perlite, expanded vermiculite, light expanded clay, and peat. A suspension of the nematode (2500 infective juveniles mL^{-1}) was applied to cucumbers 5 times in 2007 and twice in 2008, whilst an insecticide thiametoxam at the recommended dose (0.7 g L^{-1}) was used 3 times in 2007 and twice in 2008. Adults of GWF showed sensitivity to the attack of S. feltiae, and also showed sensitivity to the application of the thiamethoxam. Different control strategies had greater influence on the mean mass of cucumbers than the type of growth substrate. In the control treatment, where we found the highest number of GWF adults in both years, the mean mass of cucumbers was the lowest. In 2007, the mean number of GWF adults per leaf was significantly the lowest in treatment with thiametoxam, while in 2008 there were no differences between the influence of thiamethoxam and EPNs. Light expanded clay aggregate appeared to be a less appropriate growth substrate, as cucumbers grown on this type of substrate produced the lowest number of fruits per plant.

Keywords: Biological control, cucumbers, entomopathogenic nematodes, greenhouse, insecticide, greenhouse whitefly

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