Toxicity and Bio-Efficacy of Indole-3-Acetic Acid, A Plant Growth Regulator, Against the Greater Wax Moth, Galleria mellonella Linnaeus (Lepidoptera: Pyralidae)

Abstract

The greater wax moth Galleria mellonella L. is a dangerous pest for the apiculture industry in the world. The objective of the present study was to evaluate the insecticidal activity of the auxin plant growth regulator, Indole-3-acetic acid (IAA), against G. mellonella and its effect on the growth, development, metamorphosis and morphogenesis of this insect pest. The 3 rd instar larvae were force-fed on an artificial diet supplemented with six concentrations, viz., 100, 10.0, 1.0, 0.1, 0.01 & 0.001ppm of IAA. The most important results could be summarized as follows. IAA exhibited the strongest acute toxicity on larvae at the higher two concentrations. At other concentrations, various degrees of toxicity on larvae were found in a dose-dependent course. No pupae or adults were produced at the higher two concentrations. IAA failed to display chronic toxicity on the developed pupae. All emerged adults died at 1.00ppm of IAA but no adult mortality was observed at the three lower concentrations. LC50 value was calculated in 0.24 ppm. IAA enhanced the treated larvae to grow with increasing weight gain. Also, it promoted the treated larvae, since the growth rate increased with the increasing concentration. IAA exhibited a retarding effect on the pupation, only at the higher two concentrations. The larval and pupal durations were significantly prolonged, in a dose-dependent manner. On the other hand, IAA failed to disturb the hormonal regulation of the development program, since no intermediate creatures were produced. Also, it failed to disrupt the pupal morphogenesis, since no pupal deformities had been observed.