Ecological aspects of Aphidius colemani Viereck (Hymenoptera: Aphidiidae) on the Sitobion avenae (Fabricius) (Hemiptera: Aphididae) population in wheat culture in Medianeira, PR.

Abstract

Aphids were the main winter-cereal problem in the 70’s in southern Brazil and it was necessary to use chemical control to avoid losses. Based in the weak performance of native parasites, 14 species of exotic parasites were introduced in 1978, and in 1984 the West of Paranà’s Biological Control Program was implanted. This program propitiated the reduction of the Aphid population as well as chemical applications in the field. However, no bibliographic study was found referring to the ecological aspects of the parasites nor about Aphid’s biological control in Western Paraná´s region wheat production motivating the development of this study. Week evaluations in 25 parcel of 25 m2 were performed where 100 wheat plants were collected, from which aphid and bugs were taken out. It was observed the presence of an Aphid specie, Sitobion avenae (Fabricius) (Hemyptera: Aphididae), the primary parasite Aphidius colemani Viereck (Hymenoptera: Aphidiidae), and hyper parasitoids, and also the presence of predators. S. avenae population zenith occurred in the beginning of budding and bugs appeared a week after the aphids. Aphid control was considered efficient at 95% total parasitism. Population zenith of A. colemani occurred in the beginning of August, while hyper parasitoids zenith occurred the following week. Aphid population growth was significantly influenced by the air relative humidity, whereas parasite population was influenced by temperature and aphid population density.