Effect of Nitrogen Fertilizer Application on Population of Green Peach Aphid (Myzus persicae) on Garden Pea (Pisum sativa) in Tharaka Nithi County, Kenya

Garden pea (Pisum sativa.z) is an annual crop in Kenya, for horticultural export. The green peach aphid (Myzus persicae) is one of the most important pests. Nitrogen fertilizers have been increasingly used to most annual crops to improve crop production. However, excessive nitrogen fertilizer application has been found to aggravate aphid infestation. The study therefore, determined the level of infestation by the green peach aphid under different nitrogen levels on garden pea .The experiment was laid out in a Completely Randomized Block Design with four treatments replicated thrice. Treatments included: 0 g, 1 g, 1.5 g and 2 g of nitrogen foliar feed per litre of water. Data was collected weekly for 3 consecutive weeks on aphid population. It was analyzed using SAS, subjected to ANOVA and least significant difference for means separation at 5%. Highest aphid number was recorded on 2 g treatment. Treatments 1.5 g and 1g recorded lower aphid number. Control treatment had a declining aphid population. There was no significant difference on the first sampling days. However, week 3 recorded no significant difference across all treatments except on the 2 g treatment. Based on the study, it is possible to influence aphid performance by altering nitrogen level.