Effect of aphids and virus diseases on yield of seed potatoes in Kenya

Abstract

Experiments were conducted at 2 sites to determine the relationship between aphid populations, virus incidence and yields on 4 potato varieties (Solanum tuberosome). These varieties were planted at Tigoni and Kabete during short rains, October 2001 – January, 2002) and long rains, (March to July, 2002). The experimental design was completly randomised block design with 3 replicates. Sampling was done every 2 weeks from crop emergence to maturity. Aphid populations were assessed based on a random collection of 15 leaf samples per plot and virus incidence was assessed basing on number of plants infested per plot. At harvest, season, yields were measured for each treatment and compared with the average scores of aphids and virus incidence over the season. A regression analysis of this data revealed that there was a significant decrease in yields with increase in virus incidence at both sites (P<0.05). Similarlly, there was a significant decrease in yield with increase in aphid populations at the Kabete site but not at the Tigoni site. Although no significant relationship between the aphid populations and virus incidence was observed at either Tigoni or Kabete, as the populations of aphids increased, the virus incidence also increased. It is therefore, necessary to control aphid populations to reduce virus spread in order to achieve optimal yields of seed and ware potato in Kenya