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Abstract
INTRODUCTION
Green bean (Phaseolus vulgaris) is one of the most popular vegetable crops in Egypt which cultivates more than 60,000 Feddan for the export purposes to West Europe. Egypt is considered to be the first among the countries which grow and produce the green bean followed by Algeria. There are many names refer to the scientific name Phaseolus vulgaris such as kidney, common, snap, garden, streak and green bean. All beans are widely cultivated in temperate and semitropical regions. In temperate regions, the green immature pods are cooked and eaten as a vegetable. Immature edible pods are marketed as fresh, frozen or canned product. Green bean is a high nutritive food containing 6.2% protein, 0.2% fat and 63% carbohydrate with a moisture content of about 90%. The green bean crop is liable to be attacked by several insect pests, right from the early stage of growth through the late development to the post harvest stage. Many insects belonging to the orders, Lepidoptera, Diptera, Hemiptera, Homoptera, Thysanura and Coleoptera are known to attack green bean (Appendix 1). The most important of the field insects are leafminers.
Streak beans are the most susceptible to leafminers as host plants. The plants are liable to become infested during the seedling stage when the tender plants may be killed, or even throughout the plant, s life. Infected plants by leafminers are recognized by the presence of light colored streaks on their leaf blades, which are the mines that harbor the insect larvae and for this reason they call those plants as streak beans. Several small swellings at the sites of the leafminers pupation may be discovered along the plant stem down to the soil level or below. Infested plants lose their vigor and their foliage becomes pale and shriveled. Therefore, leafminers participate in damaging the plants and that reflected on yield sharing with the other insect-pests in that yield loss.
The leafminers of both genera Liriomyza and Phytomyza (Diptera: Agromyzidae) are cosmopolitan and economically important pests of many agricultural crops (Spencer, 1973). The damage by agromyzids results from larval feeding, although the formation of punctures in the leaves caused by the females resulted in a significant damage (Spencer, 1973 and Parrella et al., 1985).
The genus Liriomyza contains more than 300 species which are widely distributed in the New and Old Worlds but, nonetheless, most occur naturally in the temperate regions (Parrella, 1987). Approximately 23 species of Liriomyza have been reported as being economically important, and five of these are polyphagous, i.e. Liriomyza sativae (Blanchard), L. trifolii (Burgess), L. huidobrenbsis (Blanchard) , L. bryoniae (Kaltenbach) and Liriomyza strigata (Meigen) (Spencer, 1973). Plate 1 shows the difference between the adults of L. trifolii and L. sativae. It also shows the mines caused by the leafminers, the maggat and puper of the leafminer.
The broad bean leafminer, Liriomyza trifolii (Burgess) is one of the few polyphagous herbivorous agromyzide species (Spencer, 1973). This serpentine has a short developmental period, a high egg-laying capacity and rapidly develops insecticide