Effectiveness of spirodiclofen in the control of European red mite (Panonychus ulmi) on apple and pear psylla (Cacopsylla pyri)

The effectiveness of spirodiclofen, an acaricide and insecticide with a novel mode of action, in protecting apple from the European red mite (Panonychus ulmi) and pear from pear psylla (Cacopsylla pyri) was tested in field trials in four sites in Serbia in 2004, 2005 and 2007. The efficacy of P. ulmi control was investigated at Morović (Šid), where the effects of spirodiclofen were compared with those of fenazaquin, clofentezine, fenpyroximate and bifenthrin. Applied in 2004 at a rate of 0.096 g a.i. L-1 against the overwintering eggs of P. ulmi, spirodiclofen achieved 86% efficacy, while the efficacies of fenazaquin and clofentezine (25 days after treatment) were 84.4% and 27.8%, respectively. In the same season, spirodiclofen displayed high and prolonged efficacy against a summer population of P. ulmi: the efficacy of this acaricide applied at concentrations of 0.096 and 0.144 g a.i. L-1 was 98% and 96.9%, respectively, while fenpyroximate, clofentezine and bifenthrin achieved 43%, 59.5% and 62% efficacy, respectively (45 days after treatment). This effect of spirodiclofen against the summer population was confirmed in the same site in 2005, when 94.9- 95.7% efficacy was achieved (47 days after treatment). The efficacy of spirodiclofen, amitraz and abamectin against eggs and larvae of the first generation of C. pyri was examined at a Bela Crkva site in 2004, and in sites at Mandjelos (Sremska Mitrovica) and Bela Crkva in 2005. Applied at a concentration of 0.144 g a.i. L-1 at the beginning of hatching, spirodiclofen was found to achieve 83.2-95% efficacy, abamectin 93.5-94.9% and amitraz 78.9-95.6% efficacy (14 days after treatment). Applied in a site at Borkovac (Ruma) in 2007 at a rate of 0.096 g a.i. L-1 before hatching of the first generation larvae, spirodiclofen reduced the number of eggs and larvae of C. pyri by 72%, 82% and 89% in evaluations 18, 25 and 38 days after treatment, while abamectin and diflubenzuron achieved reductions of 92%, 95% and 91%, and 78%, 71% and 86%, respectively