Effects of coloured agronets in the management of tomato (solanum lycopersicum l.) Pests and tomato yield in kenya

ABSTRACT

Tomato (Solanum lycopersicum L.) is a valuable vegetable crop in Kenya, grown mainly by small-scale farmers.It provides food security, nutrition and income for many small-holder farmers. Despite its economic importance, tomato production faces major challenges including scarcity of high quality fruits, insect pests and diseases. Currently farmers have relied on application of pesticides to manage the tomato pests. Pesticides are expensive to the farmer and have a negative impact to the farmer, consumer and the environment. Therefore, farmers need to evaluate other pest control strategies that are safe, effective and economically viable with the aim of minimizing the hazardous effects of pesticides residues. This study investigated the effectiveness of coloured agronets against tomato insect pests, their distribution within the crop and impact on yield. The field study was conducted on station at the Kenya Agricultural and Livestock Research Organization (KALRO) at Kabete in Nairobi County. The experiment comprised of two seasons each consisting of five months period. Riogrande tomato variety was grown in a nursery and the seedlings were transplanted on the fourth week after sowing.The effects of coloured agronets were investigated over two seasons. The experimental design was complete randomized block design with six treatments each with five replicates. The six treatments were blue, yellow, silver, rainbow and white coloured agronets and the control. Each replicate was a plot measuring 3m by 1m with twelve tomato plants with a spacing of 50 cm from one tomato plant to the other. Data collection involved counting the number of the major tomato pests and their distribution within the crop (top, middle and bottom plant parts).The total ripe fruits per plot were harvested eleven weeks after transplanting depending on the ripening. They were graded into marketable and unmarketable, and their total mean number and mean weight were obtained. The causes of unmarketable tomatoes were determined. The data obtained from the field experiment was entered in excel and exported to Genstat version 14. One way analysis of variance (ANOVA) was done to compare means across the treatments. Significance was sought at 95% level of confidence limit. Post hoc analysis was performed on the data found significant and the means were separated using the Least Significant Difference (LSD). Correlation of the total yield and the total pest number was also carried out. The rainbow, yellow and white agronets significantly reduced pest infestation levels compared with the control while whiteflies (Bemisia tabaci) prefered to infest the top of the plant canopy. However, the leaf mines were more abundant in the middle of the plant canopy. Tomatoes which were harvested under the rainbow agronet treatment were the most but not significantly different from those harvested under yellow and white agronets.The African bollworm (Helicoverpa armigera) was a major cause of yield loss on the control.The results of this study showed that colored agronet covers are potentially effective technology in improving tomato yields through the reduction of pest numbers on the crop.From the results obtained from this study it is recommended that use of agronets to be included in integrated management of tomato pests in tomato production.