California Red scale: Development of a Method for Testing Juvenoids13

Aqueous emulsions of 21 insect growth regulators were tested for juvenile hormone activity against 1st-molt Aonidiella aurantii (Maskell) by spraying emulsions on the scale insects while these fed on lemon fruit. Residues of the 1st 6 available compounds were tested by spraying emulsions of these on lemon fruit and introducing crawlers onto the fruit 10 h later. These same compounds used to develop a method of testing by exposing white cap, 1st molt, 2nd molt, and adult stages of scales to their activity. Of these, mixed stereoisomers of methyl 10, ll-epoxy-7-ethyl-3,4-dimethyl-2,6-tridecadienoate and 6, 7-epoxy-3,7-dimethyl-l-[3,4-(methylenedioxy)phenoxy]-2-nonene were the most active (inhibited adult eclosion and prevented embryogenesis) at concentrations of 0.1 and 1.0%. The latter compound also inhibited adult eclosion of progeny from female treated with these concentrations 5 days after mating and suppressed the production of sex pheromone in virgin females treated in the 2nd molt with concentrations of 0.2 or 0.5%. Males were 16 times more susceptible to the activity of methoprene than females.