The effect of a new chitin synthesis inhibitor, novaluron, on various developmental stages of Tribolium castaneum (Herbst)

Novaluron, a novel chitin synthesis inhibitor (CSI), was tested against the various developmental stages of Tribolium castaneum (Herbst), at concentrations ranging from 0.1 to 100 ppm. It did not kill T. castaneum adults at these concentrations, but at 1.0 ppm it caused total mortality of third-instar larvae. Novaluron did not affect the number of eggs laid by T. castaneum adults that were exposed to treated wheat flour, but it totally inhibited their hatching after the third day of exposure at a concentration of 1 ppm. On the first day after infestation novaluron did not totally prevent hatching, even at the highest tested concentration of 100 ppm. The time needed to restore egg hatchability after adults were transferred to untreated flour depended on the concentration of novaluron used in the treatment. When the adults of T. castaneum were exposed to novaluron-treated whole wheat grains (at 1 ppm), similar effects to those of the treated flour at the same concentration were observed: egg hatching was drastically reduced. The effect of uptake via contact of adults with novaluron-treated surfaces was examined by exposing them to a mixture of untreated flour and 10% novaluron-treated sand at a concentration of 10 ppm, and only 1% of the eggs hatched after 18 days of exposure. When adults were removed from treated surfaces of Petri dishes to untreated flour, the hatching rate was again reduced by 100%. It was concluded that the contact penetration of novaluron into T. castaneum adults prevents the hatching of eggs subsequently laid.