Efficacy and timing of some new products against pear psylla (Cacopsylla pyri L.) (Hemiptera: Psyllidae): II. Spirodiclofen

Abstract. The effectiveness of spirodiclofen (Envidor® 240 SC) in the control of pear psylla (Cacopsylla pyri L.) on pear trees was evaluated in field experiments, carried out in commercial pear orchard in the village Dink near Plovdiv (Bulgaria) during 2014 – 2015. The efficacy of spirodiclofen (Envidor 240 SC ® at a dose of 600 and 800 ml/hl) in controlling this pest was compared to that of abamectin (Vertimec 018 EC at a dose 150 ml/hl). Each one of the insecticides was applied only once in the presence of predominantly "yellow" eggs and the first hatched larvae from the second generation of C. pyri. Аpplied only once at a dose of 800 ml/hl, spirodiclofen (Envidor® 240 SC) effectively reduces populations of the pest, achieving from 92.6 to 96.4% efficacy 21 days after treatment (DAT). Envidor 240 SC applied at a lower dose of 600 ml/hl had a slightly worse effect, achieving from 90.0 to 93.1% efficacy 21 DAT. The effectiveness of spirotetramat at both doses after only one application was very high and insignificantly different. In comparison with the reference insecticide (abamectin) the efficacy of spirodiclofen was slightly weaker in the first two weeks after treatment and insignificantly different at the end of the third week after the treatment (the total reduction of larvae ranged between 82.4 – 87.4% 3 DAT and 90.0 – 96.4% 21 DAT in the spirodiclofen treated plots, while in the abamectin treated plot it ranged between 92.9 – 96.5% 3 DAT and 94.0 – 98.7% 21 DAT. Spirodiclofen (Envidor® 240 SC), both tested doses gave similar results, which are significantly weaker in the first days after treatment, but significant enough and improved in time. This active substance, in contrast to abamectin, demonstrated a slow initial activity and a longer persistence. Spirodiclofen can be considered as a reliable tool to control of C. pyri and possible alternative to abamectin to prevent the risk of resistance in pest populations