Management of Thrips in French Bean by use of integrated Pesticide application regimes in Embu East and Mwea East Districts

Abstract

French beans (Phaseolus vulgaris L.) are major vegetables produced for the export market in Kenya. A study consisting of a survey and field experiment was undertaken in Mwea east and Embu east districts to develop an integrated thrips management regime suitable for small scale growers. The survey included 70 farmers, where 32 and 38 were from Embu east and Mwea east respectively. Multistage sampling technique was used to collect information on constraints that hinder French beans production, insect pests, and pest management practices, how decisions to control pests are made, pesticides that are used for pest control, and marketing and certification status of the farmers. Field experiments were carried out over two growing cropping cycles in Embu east district between June and December 2012. Spray regimes evaluated for the management of thrips on French beans were: (i) Thunder(Imidacloprid 100g/L + Betacyfluthrin 45g/L) plus biological (Metarhizium anisopliae ICIPE 69) pesticides (ii) Thunder (Imidacloprid 100g/L + Betacyfluthrin 45g/L) plus botanical (Azadirachtin 0.15%) pesticides (iii) Conventional(Imidacloprid 100g/L + Betacyfluthrin 45g/L, Deltamethrin) pesticides (iv) Botanical (Azadirachtin 0.15%) plus biological (Metarhizium anisopliae ICIPE 69) pesticides (v) Biological(Metarhizium anisopliae ICIPE 69) pesticides. Plots with no chemicals application were included as control in a randomized complete block design with four replicates. Data was collected on population of adult and larvae thrips, pod yield, and price per kg of marketable pods. Benefit-cost analysis for each spray regime was calculated. Results indicated that most of the farmers in the study area considered French beans farming as an important source of income, and up to 50% of the farmers had been in French beans production for a period of three years and more. Less than half of the farmers had access to agricultural extension services from the government and exporters field staff, the rest relied XVI on fellow farmers and relatives for information on French beans production. Sorting and grading were the major post-harvest activities practiced at farm level, rejects from sorting and grading were mainly used as livestock feed while local consumption of French beans was minimal. Over 70% of the farmers interviewed had good knowledge of insect pests and diseases. However, their knowledge of other pest management strategies was inadequate and was entirely dependent on synthetic pesticides. White fly was the major insect pest while rust was the major disease as identified by most of the farmers. The main marketing channels used by farmers were brokers and exporters. Less than 30% of the farmers were involved in implementation of GLOBALG.A.P with 3.1% of the farmers certified. Thrips species identified were Megalurothrips sjostedti (Trybom), Frankliniella schultzei (Trybom), and Frankliniella occidentalis (Pergande). Among the three species, Megalurothrips sjostedti (Trybom) was the most abundant whereas Frankliniella occidentalis (Pergande) had the least population. The adults were the most encountered form compared with the larvae that had a lower infestation. Chemical plus biological was the most cost effective spray regime causing more than 69% thrips reduction, and 50% increase in yields, while botanical plus biological was the least effective spray regime causing less than 20% thrips reduction, and 30% increase in yields compared to the negative control. The findings showed that farmer’s pest management practices were incompatible with good agricultural practices and export market standards andthat integrating chemical, biological and botanical pesticides can effectively reduce thrips infestation. Thereis need for farmers to be sensitized on the use of alternative pest control methods and requirements of the export market standards.