A preliminar survey on the biological control of South American tomato pinworm with the parasitoid Trichogramma pretiosum in greenhouse models

Greenhouse tomato cropping is economically advantageous for the producers. However, the hot and dry environment inside the greenhouse is conducive to tomato pinworm Tau absoluta (Meyrick) population growth and as a consequence it is difficult to control the pest. Nowadays, the pest is controlled mainly by insecticides. The biological control using the parasitoid Trichogramma pretiosum Riley is pointed out as one of those alternative methods and was evaluated in greenhouse. Experiments were carried Out in stacked plants of tomato cv. Larissa, in three greenhouse roof models: arc.. chapel and convective, with 288 plants in a 160m(2) area in each type of greenhouse. All treatments were associated with weekly sprays of Bacillus thurigiensis and weekly release of the parasitoid: 1) convective greenhouse: one single release of 200 cm(2) of parasitized eggs, once a week; 2) arc roof greenhouse: release of 200 cm(2) of parasitized eggs twice a week, 100 cm(2) in each release; 3) chapel greenhouse model 400 cm(2) of parasitized eggs release twice a week, 200 cm(2) in each release. Once a week, 50 leaflets were collected in each greenhouse. The number of eggs/leaf was determined in the laboratory and then the eggs were kept individually in a chamber in order to determine the number of emerged larvae or the number of parasitized eggs. Tomato production and damage to the fruits were determined weekly in 50 tomato plants randomly chosen in each treatment. The technical and economic efficiency of production system were analyzed in the different greenhouse models. The main results were: a) different conditions of temperature and humidity affected parasitoid performance, b) biological control technique provided tomato production for twelve weeks in all greenhouse tested c) the tomato produced in convective roof greenhouse model provided better income as shown in the economic analysis.