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Toxicity of selected biorational insecticides to Pulvinaria aurantii Cockerell and its predator, Cryptolaemus montrouzieri Mulsant in citrus field

ABSTRACT The citrus cottony scale, Pulvinaria aurantii Cockerell, is the most important pest of citrus orchards in northern Iran in recent years. Owing to the harmful impacts of chemical insecticides, the use of biorational pesticides seems a safe and convenient way to control this pest. The present investigation was set up to study contact toxicity of various biorational and chemical compounds on the first, second instar nymph and overwintering adult of the citrus cottony scale, P. aurantii, and its predator, Cryptolaemus montrouzieri Mulsant under field conditions. The results indicated that the highest percentage of mortality of first instar nymph of the citrus cottony scale was observed in the Dayabon treatment of 9 and 10 ml/L, 100.0% ± 0.0% and the lowest percentage was observed in Palizin treatment of 1.5 ml/L, 34.7% ± 2.9%. In the second instar nymph, the highest mortality was seen in the Dursban treatment of 2 ml/L, 94.7% ± 2.4% and the lowest mortality in the Palizin treatment of 1.5 ml/L, 30.0% ± 2.3%. Also, for overwintering adults Dayabon 10 ml/L caused the highest mortality, 96.0% ± 4.0% during 24 h. In the case of ladybird insects, the highest and lowest percentage of mortality was observed in the Dursban treatment of 2 ml/L, 76.7% ± 8.8%, Dayabon 5 ml/L, and Palizin 2 ml/L, 3.3% ± 3.3%, respectively. The highest and lowest mortality rate of larvae of ladybird was estimated in the Dursban treatment of 2 ml/L, 83.3% ± 3.3% and Dayabon 5 ml/L, 3.3% ± 3.3%, respectively. Also, for overwintering predator adults Palizin 1.5 ml/L had the lowest mortality, 3.3% ± 3.3% during 24 h and this rate remain unchanged after 96 h after treatment. According to the results obtained, treatments with Dayabon 9 and 10 ml/L, can be a viable alternative to other high-risk chemical pesticides in addition to effectively controlling citrus cottony scale without having any adverse impacts on predator ladybird.