Effectiveness of Available Insecticides against the Solanum Mealybug, Phenacoccus solani（Hemiptera: Pseudococcidae）

The solanum mealybug, Phenacoccus solani Ferris(Hemiptera: Pseudococcidae), has become a serious pest with the extension of the IPM system based on biological control using natural enemies. We tested the efficacy of available insecticides in the laboratory and eggplant fields. Laboratory experiments were performed under a controlled environment of 25°C and 14L:10D using green bean leaflets. To distinguish each developmental stage of P. solani, the body length and developmental time were investigated every day. We were unable to distinguish the different developmental stages of the mealybugs by body length; however, we could estimate the developmental stage from the number of days from birth(day-age). The estimated developmental stages in terms of day-age were below 4 days for 1st instar nymphs, 8–9 days for 2nd instar nymphs, 14–16 days for 3rd instar nymphs, and over 25 days for female adults. Fourteen insecticides were tested against 2nd and 3rd instar nymphs and female adults. Three chemical insecticides (acetamiprid, nitenpyram, and sulfoxaflor)and two spiracle-blocking insecticides(decanoyloctanoylglycerol and hydrogenated starch hydrolysate(HSH))were particularly effective. The efficacy of selected insecticides (acetamiprid, sulfoxaflor, and HSH)was also evaluated in a greenhouse. The results showed that sulfoxaflor was the most effective, with acetamiprid in second place, and HSH in third.