A guide to IPM in French beans production with emphasis on Kenya

Abstract

French beans (Phaseolus vulgaris L.) are a major export vegetable commodity in many horticultural crop producing countries. such as Kenya. Most of the crop is grown by smallholders and virtually all is exported to Europe. Estimates indicate that up to 50,000 smallholder families are involved in French bean production In Kenya. Recent data show that almost 100,000 people earn an income from French bean production and another 500,000 derive income directly from export of this crop. French beans can be harvested 45 days after planting and are immediately paid for upon delivery. They thus constitute a crop that provides for the daily needs of many smallholder families. However, recent export figures show a slight decline. This can be attributed to a variety of factors: In addition to meteorological and macroeconomic factors, difficulties in protecting the crop against insect pests and diseases have contributed to a large extent to the decline in the sector. French beans are attacked by a number of different pests. The most important pests and diseases are bean flies, bean flower thrips, aphids, pod borers, bean rust, red spider mites and various root diseases. The severity of infestation of different pests varies depending on the location and season. Farmers have relle(l in the past on controlling the various pests by application of foliar pesticides, especially insecticides. Pesticide applications are frequent, between 4-12 times in a crop cycle. This high application 'frequency is particularly worrisome, considering the short growing cycle of the crop (a crop may take only 12 weeks in the field). Furthermore, harvesting is done daily or every other day. As a result, farmers observe extremely short pre~harvest intervals of a few days or even one day only. The introduction of the maximum residue levels for export vegetables by the European Union (EU) is a potential complication for the export industry because of the difficulties of ensuring compliance by a large number of smallholder growers with safe plant protection measures. By July 2001, European Union (EU) countries will have zero tolerance levels for pesticides in fresh agricultural produce. Growers will have to ensure that vegetable beans are produced with a minimum number of pesticide applications and that pre~harvest intervals are strictly observed. It Is within this context that the GTZ-IPM Horticulture Project initiated work on developing an integrated pest management (IPM) system for French beans. This project was later incorporated into the Horticultural Crop Pests Sub-Division of the International Centre of Insect Physiology and Ecology (ICIPE). This IPM system Is based on the concept of avoiding the application of foliar pesticides for as long as possible, the idea being to give natural control agents a chance to keep pest populations at low levels. The second major principle is avoiding the application of any pesticide after the onset of pod formation , because none of the common commercially available pesticides registered for use has a waiting period of only two days or less. This manual describes and outlines the biology of the main French bean pests and diseases and the damage they cause. A summary of the available control options is provided. The manual also recommends IPM options, including the IPM concept developed for Kenya by the GTZ- and ICIPE-IPM Horticulture Project.