Combined effect of some bio-agents on the grasshopper, hetiracris littoralis under semi-field condition
Ecologia Balkanica 2013; 5(1) : 107-117
LC50 of the alchoholic-80% extract of Euphorbia pulchrrima (0.714%), essential oil of Garlic plant Allium sativum (0.067%) and nematodes of Steinernima sp. and Heterorhabditis sp. (500 IJs/ml), were tested for their solely and/or combined toxic effects and for their effects on some biological aspects against the grasshopper, Heteracris littoralis 1st instar nymphs under semi-field condition. The joint action of the mixture of the most effective extract (E. pulchrrima) and oil (Garlic oil) exhibit an antagonistic effect with co-toxicity index of (–24), despite the increase the proportion of death in the mixture for all the tested groups the type of interaction were antagonism, all the tested materials had variable mode of action which resulted in significantly antagonistic effects. Euphorbia 80% methanol extract and Garlic oil may use separately or in combination as alternatives safe tools against H. littoralis grasshopper. Semi-field experiments cleared that nematodes in combination with the oil or extract increased the mortality percentage. The combination mixture of extract, oil and nematode significantly affected development, reproduction and life cycle of H. littoralis. Lethal effect varied with regard to the nematode species. Semi-field experiment of the plant extract, plant oil and their mixture revealed some changes on the biological aspects, an increase in the nymphal period, pre-oviposition, oviposition and post-oviposition periods. There is vigorous decrease in the female fecundity and fertility. The control of the insect by nematode and sub-lethal dose of plant extract or plant volatile oil as biological control may enhance their lethal effect on insect pest when applied simultaneously. Combination mixture of the tested bio-agent could be considered as possible means for use in programs of integrated pest management of H. littoralis grasshopper.