Evaluation of SpinTor™ Dust in the Protection of dried Tilapia niloticus against Dermestes maculatus (De geer) (Coleoptera: Dermestidae)

Abstract

Introduction: Dermestes maculatus is a major pest of stored fish in Nigeria causing as high as 50% weight loss. Fishermen spray insecticides injudiciously which include Gamallin 20 which constitute danger to human health. SpinTor dust (Spinosad) is a commercially reduced-risk pesticide that is naturally derived from the fermentation from a soil bacterium, Saccharopolyspora spinosa. Objectives: No reference data on its efficacy in suppressing major insect pest of stored fish have been published. This paper therefore evaluated the efficacy and residual effect of SpinTor dust against Dermestes maculatus on dried Tilapia fish, Tilapia nilotica. Methods: Disinfested Tilapia was treated with 0.125, 0.25, and 0.5 percent Spintor dust. D. maculatus was introduced into containers holding 50g of untreated and treated fish.  Residual effect of Spintor was evaluated at 30 and 60 days after treatment (DAT). Results: SpinTor dust was more toxic on adults D. maculatus with LD₅₀ of 2.338 than on the larvae with LD₅₀ of 2.693. Adult mortality was highest in the dried Tilapia niloticus treated 0.5% SpinTor dust and least in the control. No larva developed in 0.5% concentration while 629 larvae developed in the control. A significant higher number of F1 adults that emerged from (0.5% concentration) treated adults died when compared with all the other treatments and control. Histopathological test on the liver of mice showed no significant weight gain in mice fed on treated fish and the control after three months. The histopathological test of the liver of the control treated  mice had no alterations in their hepatic lobes. Conclusion: Spintor dust can be used to protect dried fish against D. maculatus

Key words Toxicity, Spinosad, Dried fish, Mortality, LD₅₀, Residue, liver and Mice.