Biological Control of Cereal Aphids on Barley Plants by Field Release of the Predator, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), in Integration with the Natural Role of the Parasitoid, Aphidius matricariae Hal. (Hymenoptera: Aphidiidae)

Abstract

Barley plant is considered as one of the most important feeding source of carbohydrate for man and livestock. Four different aphids' species were recorded attacking barley plants which were; the bird cherry-oat aphid, Rhopalosiphum padi (Linnaeus) (which was the most abundant aphidś species), the corn leaf aphid, Rhopalosiphum maidis (Fitch), the green bug, Schizaphis graminum (Rondani) and the English grain aphid, Sitobion avenae (Fabricius) (Homoptera: Aphididae). The parasitoid, Aphidius matricariae Hal. (Hymenoptera: Aphidiidae) was the only primary parasitoid species recorded parasitizing the different surveyed cereal aphidś species. Results cleared strongly the natural important role of the parasitoid as a biocontrol agent against cereal aphids. Two common predatory species were
recorded preying on cereal aphids on barley plants; they were Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) and Coccinellidae predators (includingː Hippodamia convergens (Geur.) and Coccinella undecimpunctata L.). Percentage of aphidś individualś reduction after releasing second instar predatory larvae of Ch. carnea per season was estimated as 46.82%, while it was evaluated as 90.01% after 3 weeks from releasing date. Also, releasing second instar larvae of Ch. carnea indicating that, predatory larvae were effective as a suitable larval stage to be released. In addition, there were increases in case ofː means total length (cm.) per one spike for those spikes of no terminal hairs or with terminal hairs, means total spike weight (gm.), mean total numbers of grains per one spike, total weight of 100 grains and percentages of newly barley grainś germination. This situation revealed that, releasing
second instar larvae of Ch. carnea has decreased the infestation degree caused by cereal aphids and therefore had improved barley plants development, which were positively and directly reflected on the increase happened (in released area in comparing with unreleased one), in the two cases of investigated resulted yield crop. Therefore, this study was made to direct the highly efforts towards increasing cultivating barley areas side by side with that of cultivated ones of wheat. The released predator Ch. carnea can be mass reared released and integrated with the natural role of both of the parasitoid, A. matricariae and predatory species of Coccinellidae, for controlling cereal aphids on barley plants. Where, this application could be strongly encouraged and used as a component of Integrated Pest Management (I.P.M.) programs.