BIOLOGY IMPACT OF THE APPLICATION OF INSECTICIDE ENDOSULFAN IN A MELON AGROECOSYSTEM. LOS SANTOS, PANAMA, 1996-1997.

Abstract

The aphids are insects of great importance in the melon cultivation, mainly during the dry season and one of the most used insecticide for its control is the endosulfan. In melon agroecosystem, many natural enemies of the aphids exist that can be affected by the application of this insecticide. It was established trials with the objectives to determine the impact of the application of the endosulfan on the natural enemies of Aphis gossypii and the presence of the insecticide residues, as much in vegetal weaves as in the soil. Four treatments were evaluated disposed in a design of Completely Randomized Block. the treatments were the following: endosulfan + fenitrothion applied alternatingly; endosulfan, fenitrothion and the producer practices. Fenitrothion was included as reference, since it is one of the insecticides that exert an effective control of the aphids. The experimental unit consisted of two ruts of 11.0 m of length by 3.0 m of wide. In order to determine the effects of the endosulfan were realized weekly samplings of the insects; and were taken samples from leaves and ground, two hours after the first and 10 days after the last application. The sample of the fruits was taken during the first harvest. A. gossypii appeared to the 16 days after sowing (dds) and the populations were being increased in the measurement that advanced the dry season. Chrysoperla carnea and Cycloneda sanguinea appeared at the 21 dds. For the incidence of aphids (% of colonized leaves), the statistical analysis for each sampling showing highly, significant difference in all the dates, being the best treatment the practice producer. Similarly, it happened when the intensity of attack was analyzed (number of colonies by leaf, in percentage). The results in the case of C. carnea and C. sanguinea, although its incidence was low, indicated that when insecticide was applied the populations diminished. With the producer practice only in one of the samplings (6 of March) the presence of C. carnea was determined, being demonstrated the negative effect of the application of insecticides. There was no significant difference for the variable yield; however, the best yields were obtained with endosulfan + fenitrothion alternated (12.583 kg/ha) and with technology of the producer (12.217 kg/ha). The residues in the fruit, the leaves and in the soil, were below the allowed levels, being demonstrated that the endosulfan is disturbed easily in a relatively short period.