Yield loss in trellised tomato affected by insecticidal sprays and plant spacing

Crop life analysis was used to investigate the effect of two management methods: within-row plant spacing and insecticidal sprays on yield losses and pest damage on staked tomato plants. The mean tomato fruit yield was 21.4 t.ha(-1) but the cumulative fruit loss was 76.9%. The correlation coefficients indicate that the cumulative losses were more influenced by the fluctuation of fruit losses (r = 0.61) (P<0.05) than by other production factors. Fruit losses were mainly due to infestation by the lepidopteran pests Helicoverpa tea (r = 0.68) (P<0.05), Neoleucinodes elegantalis (r = 0.63) (P<0.05), and Tuta absoluta (r = 0.57) (P<0.05), and the pathogen Alternaria solani (r = 0.60) (P<0.05). Untreated tomatoes yielded less fruit, mainly due to a greater infestation of;r: absoluta, with the highest yield on tomatoes treated with the insecticide cartap. The insecticide abamectin mixed with mineral oil provided the best control of N. elegantalis, while abamectin and cartap sprays provided efficient control of H. tea and N. elegantalis in plants at the closer plant spacing (1 x 0.33 cm) regardless of mineral oil use. (C) 1998 Elsevier Science Ltd. All rights reserved.