ABSTRACT
Palmistichus elaeisis Delvare and LaSalle 1993 (Hymenoptera: Eulophidae) and neem oil are two control alternatives for the integrated management of defoliating lepidopterans. The aim of this study was to evaluate the acute and chronic toxicity of neem oil compared to the synthetic insecticide deltamethrin, on the endoparasitoid P. elaeisis, in generations F0, F1, F2, and F3. Females of P. elaeisis were exposed to neem solutions at concentrations of 0, 1.87, 3.75, 7.50, 15.00, 30.00, and 60.00 mg ml-1, to determine the dose-response relationship and estimate the neem LC50. The sublethal effects on the parasitoid P. elaeisis in generations F0 to F3 were evaluated with these same concentrations of neem and 0.033 mg ml-1 of deltamethrin. The neem LC50 was estimated at 3.92 mg ml-1. The LC50 for P. elaeisis is 3.83 times lower than that recommended by the neem manufacturer for pest control, demonstrating high acute toxicity to this natural enemy. The chronic toxicity of both the commercial dose and those below it to P. elaeisis caused low sublethal effects. The correct concentration of neem oil in pest control is important, and its use should be performed with caution in integrated pest management programs using the endoparasitoid P. elaeisis to avoid causing interference between the two pest control techniques.
Subject(s)
Hymenoptera , Insecticides , Animals , Female , Glycerides , Hymenoptera/physiology , Insecticides/toxicity , Nitriles , Pupa , Pyrethrins , TerpenesABSTRACT
Diaphania hyalinata (Linnaeus, 1767) is one of the main pests of the cucurbit crops. Biological control and botanicals are used in integrated pest management (IPM), especially in agro-ecological agricultures where the use of synthetic pesticides is restricted. Toxicological effects of plant essential oils on target and nontarget organisms should be evaluated to determine its use in IPM. The toxicity of ginger, peppermint, oregano, and thyme essential oils to D. hyalinata eggs, larvae, and pupae and their selectivity to the parasitoid Trichospilus pupivorus and the LC50, LC99 and the relative selectivity index (RSI) of these botanicals were determined. The eggs of D. hyalinata were more sensitive to the botanicals applied than its larvae and pupae, with higher toxicity of oregano and thyme essential oils, followed by those of peppermint and ginger. Topical application was the least toxic method to D. hyalinata larvae. Ginger, peppermint, and thyme essential oils were more toxic by ingestion and oregano by contact to D. hyalinata larvae. The essential oil concentrations applied to D. hyalinata pupae prevent the emergence of adults of this insect with the oregano essential oil showing the greatest toxicity. Peppermint, ginger, thyme, and oregano essential oils were selective to T. pupivorus with RSI50 of 5.40, 1.38, 8.15, and 6.98 and RSI99 of 1.54, 2.53, 3.90, and 4.16 respectively. The ginger, peppermint, oregano, and thyme essential oils were toxic to immature D. hyalinata and selective to T. pupivorus females presenting potential as an alternative control in the IPM of this pest in Cucurbitaceae crops.
