Effect of biological and chemical insecticides on Spodoptera species (Lep., Noctuidae) and marketable yields of tomatoes

Various biological and chemical insecticide treatments were evaluated again st beet armyworm Spodoptera exigua (Hubner), yellowstriped armyworm Spodopt era ornithogalli (Guenee) and southern armyworm Spodoptera eridania (Cramer ) to determine their effects on Spodoptera species, fruit quality and marke table yields of tomatoes Lycopersicon esculentum Mill. Biological insectici des included several Bacillus thuringiensis (Berliner) products including C ondor(R) OF, Dipel(R) 2X, Javelin(R) WG, Bactec(R) III, Biobit(R) FC, Cutla ss(R) WP and Lepinox(R) G. Other biological treatments included a baculovir us, SeNPV isolated from S. exigma, and an entomophagous nematode, Steinerne ma carpocapsae Weiser. Chemical treatments consisted of several insecticide s from various classes including a carbamate (methomyl), pyrethroid (fenpro pathrin) and an organophosphate (chlorpyrifos). A natural extract from the neem tree azadirachtin and an untreated control were also included in the e valuation studies. Population densities of S. exigua were below the economi c threshold level in control plots and there were no significant difference s for small, medium and large larvae. Densities of S. ornithogalli and S. e ridania larvae exceeded the threshold level and significant treatment diffe rences were observed in their populations. Fruit injuries were significantl y higher in nonefficacious treatments that included S. carpocapsae, SeNPVs and untreated controls. Average weight per fruit was not significantly affe cted by treatment rates of applications, but total marketable yields were s ignificantly higher in efficacious biological, chemical and combination tre atments compared with the control.