Effects of Two IGRs, Buprofezin and Pyriproxifen, on Icerya Purchasi Maskell (Homoptera: Margarodidae)

The effectiveness of Buprofezin (40% SC) and Pyriproxifen (10% EC) on the mortality of nymphal stages and fecundity of cottony cushion scale was investigated under glasshouse conditions. The LC50 of IGRs was also determined for the first nymphal stage. Two applications were conducted at intervals of 1 day prior to introduction of crawlers and 42 days after infestation. The results indicated that Buprofezin was superior to Pyriproxifen in suppressing the growth and development of crawlers. The mortality of first instars was determined 28 days after the first application. Although the total mortality of second instars due to Pyriproxifen was higher than that by Buprofezin, but the cummulative mortality of 1000 ppm treatment was estimated to be 100% in both experiments after 42 days. The effect of Buprofezin on incomplete molting of nymphs and its ovicidal activity showed a decreasing rate in third instar nymphs survival and fecundity of cottony cushion scale in relation to different concentrations of the IGRs, but it never reached 100%. Meanwhile the 1000 ppm concentration of Pyriproxifen in the same treatments brought about complete mortality to third instar nymphs and inhibited adult and egg formation due to imbalanced juvenile hormone activity. However in 1 ppm concentration of Pyriproxifen, a noticeable increase in fecundity of cottony cushion scale was observed.