IMPACT OF SYNERGISTISM WITH COMBINATIONS OF SILICON OIL, CLOVE OIL AND SULFURIC ACID ON THE TOXICITY OF SOME INSECTICIDES AGAINST COTTON MEALYBUG, PHENACOCCUS SOLENOPSIS (HEMIPTERA: PSEUDOCOCCIDAE)

Cotton mealybug, Phenacoccus solenopsis is a severe threat to cotton crop in Pakistan and its control at ovisac as well as at adult female stage is very difficult with insecticides because eggs/nymphs inside the fluffy ovisac and adult female due to its thick waxy body coating avoid the exposure to insecticides and survive successfully. The present research was carried out under laboratory conditions to investigate effect of silicon oil, clove oil and sulfuric acid in different ratios (1:1:1, 2:1:1, 3:1:1, 4:1:1 and 5:1:1) with synergistic impact on the toxicity of nicotinoids (nitinpyram and thiacloprid), IGR (pyriproxifen) and supracide (used as standard) or not. The results revealed that co-administration of all combinations of silicon oil, clove oil and sulfuric acid in different ratios caused two and three times increase in the toxicity of evaluated insecticides against adult female and ovisac stage of cotton mealybug, respectively. The mortality was observed very high ( 90%) even at the five times less insecticide quantity (100 ml) than the highest insecticide quantity (500 ml) of the FRD solution. All the ratios among silicon oil, clove oil and sulfuric acid induced statistically similar impact on the toxicity of evaluated insecticides. The nicotinoids as well as IGR, which are considered soft and biorational as comparative to highly toxic supracide, caused 90-100% mortality in the both target stages of cotton mealybug and were found nonsignificantly different from supracide in toxicity when evaluated alone or in combination with wax dissolving agents (WDA). Results indicate that soft and bio-rational insecticides like nicotinoids (Nitinpyram and Thiacloprid), IGR (Pyriproxifen), in combination with 1:1:1 of silicon oil, clove oil and sulfuric acid, at 1:1/100 of WDA as well as of FRD solution should be evaluated under field conditions on cotton before final recommendation.