Interaction of English Grain Aphid, Sitobion avenae (F.) and Their Natural Enemies to an Agro-forestry Environment

The agro-forestry landscape can influence the distribution of wheat-feeding aphids and their natural enemies. Aphid population densities were significantly higher in the arable control areas compared to the arable alleys. The ratio of alate to apterous adults indicated that relatively higher numbers of alates were found in the control areas. The apterous S. avenae adults and nymphs combined were found to constitute approximately 97 % and 98 % of the total from the arable alleys and arable control areas respectively. Parasitism rates (the proportion of aphids that were mummified) were 12.80% and 7.60% in the arable alleys and control areas respectively. In contrast, the numbers of mummies per aphids were found to be lower in the arable controls. The small-scale variation in the distance of plants from the tree rows did not significantly influence insect abundance.