Abstract:
Tomato spotted wilt (TSW) disease was recently reported to be endemic and posing a threat to cucumber production in Nakuru district. A study was conducted to determine the response of commercially available cucmnber varieties to the disease, the effect of time of onset on disease severity; and the effect of type of mulching material on vector population, field infection and yield. The study was carried out both in the glasshouse and in the field. In the glasshouse four varieties (Ashley, Marketer, Super Marketer and Chinese) were inoculated at cotyledon, 3-4 leaf stage and flower bud stage of growth and evaluated for disease severity. Plants were arranged in a split plot design replicated four times. In the field, the experiment was set up in a complete randomised block design (CRBD) in a 2 by 8 factorial layout. Two varieties (Ashley, Marketer) were raised on 7 types of mulches (red, yellow, silver, clear, black, white, and straw), with unmulched plots as the controls. Variety Marketer was more tolerant to the disease compared to other varieties. All the varieties were generally tolerant to the disease at the cotyledon stage. At the 3-4-leaf stage and the flower bud stage the plants were however susceptible to the disease. Mulching had a significant effect (pg 0.05) on thrip population. Silver and clear mulch significantly (pg 0.05) suppressed the thrip populations and TSW. Hence silver and clear mulched plants had higher marketable and total fruit yields. Straw and black mulches decreased the crop’s marketable yield. Yellow, white and red mulches increased fruit weight by about 60% but there was no corresponding increase in marketable yield probably because of the high thrip population and disease levels. Variety Marketer was highly tolerant to the disease compared to Ashley under field conditions. Planting variety Marketer, controlling the disease at the vegetative stage (3-4 leaf stage) and the reproductive stage (flower bud stage), and mulching using silver or clear mulch are important components of an integrated pest management programme of TSW
