Chemical Control of Agrican Bollowrm (Heliothis armigera) (Hubner) with ultra-low-volume sprays.

Experiments consisting ofUltra-Low-Volume (ULV) formulations of endosulfan (500 and 750 g active ingredient (a.i.)/ha), icypermethrin (150 g a.i./ha), fenitrothion (960 g a i/ha) Selecron 250 VLVAIR (750 g a.i./ha) and an untreated check were conducted for two consecutive years against Heliothis armigera on haricot beans at the Awassa and Nazareth Experiment Stations of the Institute of Agricultural Research (IAR),Ethiopia. The treatments were replicated five times in a randomized complete block design on 20m by 20m plots. Of the insecticides used, single application ofcypermethringave a more consistent and significant control than the check in both seasons at both stations. A new product,ypermethrin/Profenofos 166R,substituted for fenitrothion at Nazareth in the 1980 season gave promising results to warrant further testing. Endosulfan, a recom- mended insecticide against American Bollworm in the past, was not as satisfactory as cypermethrin in the control of American Bollworm on haricot beans. Of the twelve to twenty species of grain legumes grown in Ethiopia, haricotean (Phaseolus uulgaris) is the most important as an export crop (5,7). For example, of the 25, 409 metric tonnes of pulses exported in 1978/79, haricot bean accounted for nearly 61% of the total tonnage and was a source of Bin- 11,242,000 (US S5,430,900) revenue in foreign exchange (2). Heliothis armigera, commonly known as American Bollworm (ABW) a'ong with bean fly (Ophiomyia phaseoli) (Tryon) is the most important insect pest limiting production of haricot bean grown under rainfed condition in Ethiopia. The pest causes damage mainly by boring the pods and feeding on the developing seeds. Estimates on the loss of haricot bean due to ABW damage are not available but, on cotton, the noctuid can claim at least 40% of the costs incurred in the control of all other pests combined (11). American Bollworm is notorious for its rapid development of resistance to several insecticides (1,4). It does not lend itself to control with nonchemical methods such as "closed season" that are routinely used in the control of other bollworms like pink bollworm (Pectinophora gossypiella (Saunders)). This is because of its wide host range and periodic migratory ability from the surroundings of the crop (8,9). Consequently, periodic evaluation of promising insecticides seems to be one of the most viable options for the control of this pest. Unlike the control of ABW on cotton in Ethiopia, information on its control with ULV formulations on haricot bean is not available but the pest is known to be effectively controlled with these formulations on beans (Phaseolus sp.) elsewhere (36). If found effective, ULV insecticide sprays are expected to reduce application cost and increase efficiency since they do not require water and are applied more conveniently than the conventional water based sprays. With these objectives, experiments were carried out to evaluate the effectiveness of ULV insecticides against ABW on haricot bean under Ethiopian conditions.