Esquemas de tratamentos químicos para o controlo das principais pragas do tomate de época fresca em Chókwé

Abstract

The general objective of this work was to test different chemical treatment schemes for the control of the main tomato pests (red spider mite and American caterpillar) in the Chokwé irrigation system. Disease control was preventive with a fungicide. The experiment was carried out at the INIA agricultural station in Chókwé, between March and August 2003, using a randomized complete block design with subdivided plots. The three treatment schemes used were: (i) calendar application and, (ii) pest monitoring and application according to a pre-defined low level of population density and (iii) pest monitoring and application according to a high level of predefined population density. The pesticides used were abarenctin, an insecticide with acaricidal action for the control of red mite and American caterpillar and Mancozeb, a fake for the preventive control of diseases. The varieties used were Rio Fuego, Cal J, UG32B, these are open pollinated and fortune a hybrid. Analysis of variance showed that there were no significant differences in yield between the three treatment regimens. However, the tested varieties showed significant differences in yield when compared to each other. The Fortune variety had the best yields with 115.6 ton/ha, while Rio Fungo had the lowest yields with 67.1 ton/ha. There were significant differences between the average number of applications, and the treatment by calendar resulted in the highest number of applications. The test results also show that infestation levels and pest density were low over time and did not significantly influence yield. The treatment schemes based on pest monitoring and application according to infestation levels had a greater financial return, this being 6,481,133 Mts/ha for the lowest level and 8,007,600 Mts/ha for the highest level . The calendar application method resulted in the lowest return, which was 1,695,198.00 Mts/ha. The study suggests that biweekly treatment of the mite and the American caterpillar in the fresh season is not advisable, and that the NED should be calculated and considered when making a decision on when to carry out chemical treatments.