The lethal effects of three insect juvenile hormone analogues on the developmental stages of Ephestia cautella (Wlk.) (Lepidoptera: Phycitidae)

The juvenile hormone analogue methoprene (ZR 515) was found to interfere with normal development of Ephestia cautella in a manner dependent on dose and age. This compound was found to cause the formation of non-viable 1st instar larvae when it was given to young eggs prior to the stage of blastokinesis, but it was less effective against older eggs. Methoprene inhibited metamorphosis and produced supernumerary giant larvae when it was given to larvae 5 days prior to pupation or younger. However, when given 1–3 days before pupation, it did not prevent pupation but did prevent adult emergence. Young pupae within 1 day of pupation were also found to be very sensitive to the compound. It appears that a small ecdysteroid peak detected 5 days prior to pupation might be responsible for the transition from inhibition of pupation to defective metamorphosis. Methoprene (ZR 515) and hydroprene (ZR 512) were more effective in prolonging the larval period than kinoprene (ZR 777), which, however, was the most effective against Ephestia larvae.