Effect of Nitrogen Fertilizer on Biological Paramet ers of the Aphis craccivora (Hemiptera: Aphidiae) and Associated Productivity Losses in Common Globe Amaranth

Abstract

Reducing nitrogen status of floriculture plants is an effective tactic in pest management by decreasing host plant quality. Life table parame ters and population growth rate of Aphis craccivora (Hemiptera: Aphidiae), as well as cosmetic and qual itative parameters losses associated with aphid infestation were evalu ated in relation to N fertilization levels on Gomphrena globosa , under greenhouse condition. Four N fertilization levels (0, 30, 60, and 100% of recommended 2 kg m -3 ) were used. The results indicated that aphid’s intrinsic rate of natural increase on plants fertil ized with 100% of the recommended N level was the highest. Abundance and population gro wth rate of aphid also positively correlated with N fertilization levels. The interac tive effect of aphid population and N fertility significantly affected growth parameters of the plants. In the absence of aphid, plant yield improved linearly with increasing N lev els. However, aphid population highly decreased shoot to root ratio and the number of flo wers in plants fertilized with 100% of the recommended N level. According to our findings, fine-tuning fertility to reduce A. craccivora population is a steadfast tactic to produce market able globe amaranth ornamental plant. Keywords: Aphid performance, Aphis craccivora , Nitrogen fertilization, Plant yield, Population growth.