BIOLOGICAL CONTROL POTENTIAL OF AN APHIDOPHAGOUS PREDATORS, CANNIBALISM AND INTERSPECIFIC COMPETITION

Abstract

Aphidophagous predators have a great importance in biocenosis as bio-regulators of aphids. Specific relationships between predators, interspecific competition and cannibalism, have an important role in biological control. The focus of this study was on biological control potential of predators, interactions between larvae of Coccinella septempunctata, Chrysopa carnea, Sphaerophoria scripta, Aphidoletes aphidimyza and incidence of cannibalism. Observations were made in Prilep region (Macedonia) 2012-2015 and there was applied method of survey of 20 randomly selected tobacco stalks infested with aphids. Predatory larvae were reared with Myzus persicae in petri dishes under laboratory conditions. All experiments, prey consumption, interaction between predators and cannibalism were conducted in the laboratory. C. septempunctata, C. carnea, S. scripta and A. aphidimyza are primarily predators and they occupy the third trophic level of food chain (tobaccoM. persicae -predator). The growth of population of predators continuously follows the growth of aphid population on tobacco. During investigations, 5861 predators were determined in 2012 and 3788 in 2013. According investigations during 2013 they are voracious predators of aphids. In laboratory conditions, adults of C. septempunctata consume in average 468 and larvae 350 aphids, C. carnea larvae 458 aphids, S. scripta 333 aphids and A. aphidimyza 200 aphids. Interspecific competition and cannibalism are important factors in rearing conditions of predators. The outcome of interactions between predators 2014/2015 mainly depends on the body size of the competitors. In general large individuals behaved as predator while small individuals became prey. Eggs and L1 were extremely vulnerable in regard to larger larvae. Cannibalism in C. septempunctata and C. carnea occur when eggs or young instar larvae are kept together with larger larvae, in the absence of aphids. Predators are often used as biological control agents in Integral Pest Management, so mass rearing techniques must be developed which guarantee higher survival rates of predators.