Management of Fruitworms in Tomato.

Tomato is one of the major vegetable crops cultivated in Ethiopia. Tomato production is mainly confined to central Ethiopia. Fruitworms: African bollworm (Helicoverpa armigera) and potato tubermoth (Phthorimaea operculella) among others, are the ones responsible for both yield and quality reduction. Severe damage by these pests could render the produce unmarketable. In the light of the importance of these insect pests in the production of the crop, development of an integrated method of pest control was thought timely and appropriate. A series of experiments consisting of varietal screening and determination of critical perod of insecticidal sprays against fruitworms of tomato, Phthorimaea operculella and Helicoverpa armigera were conducted in 1991/92 at the IAR Melkassa Research Center. Four sets of varieties each consisting of 33, 23, 19 and 22 varieties were screened. Using number of damaged fruit and number of fruitworm larvae per 100 fruit as selection criteria, the varieties 'Pusa Early Dwarf, 'Pusa Early Dwarf', 'Pusa Ruby', and 'Seedathing' from the first set; 'RV-41, 'Red Pear', and 'RV-44' from the second set; 'L-97', 'CL-1131-0-0-38-4, and 'CL-5915-553-D4-3-0' from the third set; and 'CL-5915-553-D4-3-0', 'CL-5915-93-D4-1-0', and 'UC204 A' from the fourth set were found to be more resistant. Critical period of insecticidal spray was studied in a factorial RCBD with splitplots using the standard insecticide cypermethrin and the microbial insecticide Bacillus thuringiensis as main plot treatments, and application of these chemicals at different growth stages of tomato as subplot treatments. Cypermethrin gave significantly better control than Bacillus thuringiensis: an average of 19 percent damaged fruit as compared to 27 percent. Realizing the importance of these pests in the production of tomato one should give priority to those varieties which show certain degree of resistance to fruitworms attack. Although both species occur simultaneously during most stages of the crop, application of Cypermethrin at 75 g.a.i./ha once at early flowering and once at early fruiting stage of the crop would result in minimal damage from these pests.