Tomato Pest Management Practices and Efficacy of Selected Botanical Pesticides for Management of Tomato Leaf Miner (Tuta Absoluta) in Kathiani, Machakos County

Abstract

Tomato in Kenya is the second important vegetable both in production and revenue generation. In recent times, its production and yield has adversely been affected by the recently reported invasive, tomato leaf miner (Tuta absoluta). The objectives of the study were to determine farmer management practices of tomato pests and evaluate the bioefficacy of selected biorationals. A survey to determine farmer pest management practices of tomato was conducted by interviewing one hundred tomato small scale growers in Kathiani, Machakos County. A stratified sampling approach was adopted for selecting the sample size of tomato growers from a sampling frame consisting of a list of tomato producers in four administrative wards of Kathiani Sub County. In addition, on-farm experiments were conducted on small holder farms (upper midland four zone -UM 4) in Kathiani for two seasons. The experiments were laid out in a Randomized Complete Block Design (RCBD) in a split plot arrangement with four replications. Two tomato varieties; Rio grande and Tylka F1 were subjected to spray regimes that comprised of Flubendiamide (Belt®); a synthetic pesticide and botanicals; Azadirachtin 0.03% (Nimbecidine), Pyrethrum + Garlic extract (Pyegar) alone and alternate use of Nimbecidine and Pyegar as treatments compared to control. The study established that significantly (p<0.05) more men (75%) grow tomato than women and they use both rainfed and irrigation conditions to produce the crop. Tomato is grown on less than one acre pieces of land out of the 0-5 acres of land that these farmers own. Pests and diseases (43%) and inadequate capital (34%) were the main challenges reported by the growers and Tuta absoluta was considered a key pest associated with higher yield loss followed by whitefly and spider mites. Significantly (p<0.05) more farmers (93%) had observed Tuta damage in the field but did not know how to identify the pest. The study also established that significantly more farmers (74%) used synthetic pyrethroids mainly alpha cypermethrin and lambda cyhalothrin followed by the use of Flubendiamide in the management of tomato pests, Tuta absoluta included. Non chemical management options such as cultural methods intercropping, field hygiene and use of physical barrier were not commonly reported by the farmers indicating low or non-use. Farmers relied on their neighbours and agro-input dealers for agricultural information. The farmer practices are ineffective and there is need for an alternatives to reduce dependency on pesticides. Efficacy results revealed that there were no differences in leaf damage observed on tomatoes treated with Nimbecidine, Pyegar and Nimbecidine + Pyegar compared to control. However, the percentage leaf damage was much lower in tomatoes treated with either Nimbecidine or Pyegar alone. The lowest percentage leaf damage was recorded in tomatoes treated with Belt®, the standard check; while the highest damage was recorded in the control. The botanicals used and the standard, Belt, significantly (p<0.05) reduced tomato leaf miner larva infestation, compared to control. The least recorded was in Belt while highest was recorded in control. The bio pesticides Nimbecidine and Pyegar had the same effect in reducing the larvae infestation but Pyegar achieved slightly higher reduction. The botanicals used and the starndard, Belt, significantly (p<0.05) increased the number of tomato fruits compared to untreated control. Belt® recorded the highest number of fruits in both seasons and varieties followed by Pyegar in the second place while control had the least fruits in both seasons and varieties. The combination of Pyrethrum and garlic (Pyegar) and Nimbecidine are effective in reducing leaf damage, Tuta larval infestation on tomato leading to an increase in productivity. Although the botanical extracts were rarely used, the study has demonstrated that they have the potential and are effective for the management of Tuta absoluta and can be considered for its management.