DETECTION STRATEGIES FOR ADULTS OF THE GUAVA WEEVIL CONOTRACHELUS SPP.

Abstract

The guava weevil (Conotrachelus dimidiatus) is one of the most important pests of the guava crop and can cause severe fruit losses if it is not controlled. In general, guava producers use from three to ten pesticide treatments, starting with the beginning of the raining season and regardless whether the guava weevil is present or not. Currently, only the limb jarring method is used to detect the presence of guava weevil adults. However, this method, although very effective, is laborious and unpractical. The objective of the present study was to search for alternative strategies to monitor guava weevil adults. Different kinds of traps were evaluated, including traps with and without grandisoic acid (aggregation pheromone of C. nenuphar males); mesh traps placed around the guava trunk, and the limb jarring method. To obtain possible alarm pheromones, guava weevil adults were collected for extraction by different water: alcohol mixtures. The solutions were concentrated by dynamic aeration and the compounds analyzed in a gas chromatograph. The potential of the volatile products to attract guava weevil males and females was evaluated using Tedders traps. The results showed that both traps captured adults; however, the optimum number of traps still needs to be evaluated. The use of grandisoic acid did not increase captures, whereas the limb jarring method had more and constant captures. Alarm volatile graphs of concentration 20:80 showed three initial peaks and others that appear later at 10.83 to 13.26 min, which are more defined. Volatile differences between healthy and damaged fruits were present among the fastest eluting compounds (2.225, 2.54 and 2.09 min.). Under dynamic aeration two pronounced peaks were observed (7.06 and 9.34 min.) and in-between these two peaks could be some possible sexual pheromones. Finally, traps with male adults captured more guava weevil than those with females. Thus, guava weevil males responded better, a phenomenon which has also been reported for C. nenuphar.