Freqüência dos insetos na polinização e produção de algodão

Abstract

Insects frequency on cotton pollination and production. The present experiment was conducted at University Centre Moura Lacerda, Ribeirão Preto, state of São Paulo, and had the aim of studying the insects frequency and behaviour on cotton flowers ( Gossypium hirsutum L.) as well as the collection type (nectar and/or pollen) of these insects and the effectiveness of their visits on cotton production. To do so, the culture remained under observation on March, 2002, during the first five minutes in each time, from 8:00 to 17:00, with three repetitions. We also marked 50 flowers buds: 25 covered with paper bags and 25 uncovered, in order to evaluate the insects influence on fructification. The cotton flowers opened between 8:00 and 9:00 and closed between 17:00 and 18:00. The insects which were observed in the flowers were the africanized honey bee Apis mellifera scuellata (50.3%), followed by the cleoptero (brasileirinho) Diabrotica speciosa (40.8%), other hymenoptera (5.0%), other coleoptera (1.7%), lepidoptera (1.1%), and the bee Trigona spp. ( irapuá ) (1.1%). Apart form the africanized honey bee and the irapuá , all the insects collected exclusively nectar from the flowers. The africanized honey bees preferred to collect nectar (95.6%) and visited the flowers from 9:00 to 16:00, with frequency peak at 13:00. Brasileirinho visited the flowers from 8:00 to 17:00, with frequency peak at 15:00. The number of apples was not different in the treatments (covered and uncovered), however, the number of seeds was higher in the uncovered treatment (29.45 seeds/apple, on average) than in the covered one (20.65 seeds/apple, on average). The africanized honey bee was considered as an effective pollinator of this culture