Population Growth of Tomato Leaf Miner Moth, Presence of Parasitoid, and Farmer Control Strategies in Nairobi and Kajiado Counties, Kenya

Abstract

Tomato (Solanum lycopersicum) is an important vegetable crop that is widely grown for both home consumption and commercial purpose. Its demand is high both for domestic use and for market purposes. However, pests and diseases are a threat to tomato production. Currently, the most damaging pest affecting tomatoes is the invasive tomato leaf miner moth (Tuta absoluta). Research on the pest has not been documented adequately in Kenya on its population growth and effective management practices. The aim of this study was to understand the population growth of T. absoluta and to evaluate the effectiveness of the current management practices being employed by farmers within Loitokitok, Kajiado County. The study also aimed at evaluating the available indigenous parasitoid of the pest in the field. A survey was carried out to determine the status of the pest and management practices being employed by tomato growers. Factors such as educational levels, land ownership, pest diversity and management practices were documented. Specimens of larval population were collected from the field and taken to the laboratory to allow for development of parasitoids. The plant varieties used in this experiment were Kilele F1 and Rio Grande tomato. The experimental design was split plot arranged in Randomized Complete Block Design at both sites with variety and Chlorantraniliprole as factors, which was replicated three times. Descriptive statistics was used to analyze data from the survey based on percentage occurrences reported by the respondents. The Statistical Package for Social Sciences (SPSS) version 20.0 was used in analysing the data on survey. Data on larval population from both locations were subjected to Analysis of Variance (ANOVA) using SAS- computer software (SAS 9.0). The means were separated using LSD. The survey revealed that 52.3% of T. absoluta was the most important pest to tomato growers. The results also revealed that 46.4% of the respondents were using Chlorantraniliprole as the main pesticide for controlling T. absoluta. There was no significant difference P≤0.05 between the two tomato varieties in relation to T. absoluta preference. Tomato plants that were treated with Coragen® (Chlorantraniliprole) recorded 2.0±1.2 mean number of T. absoluta larval population in week 2 for the protected crops compared to 5.7±0.9 that were recorded on the unprotected plants in Loitoktok. The mean weight of marketable tomato fruits collected from the protected plants was 7.8±1.2, which was higher than the unprotected that recorded mean weight of 3.6±0.4 tomato plants in Loitokitok. The highest mean number of unmarketable tomato fruits registered 61.0±5.5 in week 4 and mean weight of 6.8±0.6kg. Neochrosocharis sp was found to parasitize T. absoluta with a parasitism rate of 1.9%. The implication of this results shows that Chlorantraniliprole was effective, as a control strategy of the pest. The population of natural enemies should be raised to control T. absoluta.