Investigating the effect of some insecticides on Pulvinaria aurantii Ckll. and its predator, Cryptolaemus montrouzieri Mulsant

The orange pulvinaria scale, Pulvinaria aurantii Ckll. is the most important scale of citrus in the northern Iran. The lethal effects of chlorpyrifos, pyripropoxyfen, acetamiprid and palazin, alone and in combination with emulsifying oil, were evaluated on first-instar nymphs of P. aurantii. The experiment was conducted under natural condition in a randomized complete block design with 3 replications and 10 treatments, and treatments effect was compared 1, 7, 14 and 21 days after spraying. Moreover, the effect of these insecticides was investigated on duration of immature stages and female longevity of Cryptolaemus montrouzieri Mulsant. The activity of some detoxification enzymes (alpha-esterase, beta-esterase and glutathion-S-transferase) in third instar larvae was evaluated. The experiments on the ladybird were conducted under laboratory conditions at 26±1ºC, 75±5% RH and a photoperiod of 14:10 (L:D) h. The treatments with acetamiprid + oil, pyripropoxyfen + oil, chlorpyrifos + oil and palazin + oil had the highest mortality on first nymphal instar of the scale. The longest incubation period of C. montrouzieri was in chlorpyrifos treatment (8.13 days), and the shortest was in control (4.80 days). Moreover, among treatments the female longevity of C. montrouzieri was the longest in control (96.60 days), and shortest in chlorpyrifos treatment (53.50 days). Chlorpyriphos and acetamipirid caused the highest reduction in alpha-esterase and glutathion-S-transferase activities of the third larval instar of C. montrouzieri, respectively. Also, palizin had less negative effect on the activity of beta-esterase in comparison with other tested insecticides. The results of this study indicated that among tested compounds, palizin in combination with the oil is a suitable compound to control of the orange pulvinaria scale.