Estudos bio-ecologicos de Bracon vulgaris ashmead (Hymenoptera: braconidae), ectoparasito de anthonomus grandis Boheman, 1843 (Coleoptera: curculionidae)

AUTOR(ES)
DATA DE PUBLICAÇÃO

1994

RESUMO

The objetive of this work was to investigate ecological aspects and comparative biology of Brcron vulgaris Ashmead (Hymenoptera: Braconidae), an ectoparasite of both Anthonomus grandis BOHEMAN, 1843 (Coleoptera: Curculionidae), the boll wevil and Pectinophora gossypiella SAUNDERS, 1843 (Lepidoptera: Gelechiidae), the pink bollwonn, which are considered as key pests of cotton in Brazil and several other countries. These investigations were carried out under field and laboratory conditions. Field observations were conducted during 1991-1992 in two untreated plots and one subjected to integrated pest management program, in wich the diversity of existing natural enemies were preserved at maximum level. Reproductive structures (cotton squares, flowers and cotton bolls) either attached to plants or fallen on floor, were surveyed weekly. These structures were examined for the presence of eggs, larvae, pupae or adults of the parasite. Observations were carried out during the whole cotton season at different phenological stages of the plant. Damages caused to plant structures (cotton squares, flowers and cotton bolls) and the rate of parasitism were also evaluated during the investigations. Plant structures were examined using sterioscopic microscope in the laboratory. In case of parasitized larvae of A. grandis and/or P. gossypiella were transfered to a glass jar covered with a piece of nylon cloth and incubated at 27°C up to the emergence of adults. After emergence, the adults were transfered to rearing cage of 50x50x50 cm and covered with a fine transparent cloth; food a l00% honey solution was provided. For host adaptability to B. vulgaris, five hosts species were used: A. grandis, Anagasta kühniella, ZELLER 1879 (Lepidoptern: Pyralidae), Spodoptera fiugiperda J.E. SMITH, 1797 (Lepidoptem: Noctuidae), Anticasia gemmatdis HÜBNER, 1818 (Lepidoptem: Noctuidae) and Alabama argilacea HÜBNER, 1818 (Lepidoptem: Noctuidae). The host larvae were placed in dried petioles of Ricinus communis previously soaked in cottons square extract and sealed at both ends with cotton and were offered to female parasites in Petri dishes for 24 hours. After this hour, the Petri dishes were removed and the larvae inside the petioles were examined. The parasitized larvae were then reincubated and were assessed every 24 hours intetval up to adult emergence. The same procedures was used to evaluated P. gossypiella as a host in a separate treatment. The atractivity of parasites to diferent plant extracts (cotton squares, cotton bolls and leaves) were deternined using the identical method as host adaptability. Only water was used for control treatment. The results indicated that the parasite population fluctuated with the host population with tendency to increase in parasitism from the middle to the end of the crop cycle. The highest rate parasitism was observed in A. grandis larvae on plant reproductive structures still maintained on plants. The highest rates of parasitism were observed in A. grandis under field conditions were: 28,7% at Santo Antonio de Posse; 85% at Cosmópolis and 67,57% at Casa Branca. lhe rate parnsitism recorded for P. gossypiella larvae was much smaller than A. grandis at field conditions, though at laboratory conditions the rate of parasitism was always high, sometimes reaching 100%. Host preference studies indicated preference for A. grandis and A. kühniella by the female parasite. These two hosts also showed the best suitability to the parasite development. In relation to plant extracts, cotton squares attracted most parasite females followed by cotton bolls and leaves extracts. B. vulgais proved to have a high potencial to control the populations of A. grandis on cotton plants and showed to be a very promissing agent for the Integrated Pest Management Program against cotton boll worn and pink bollworm

ASSUNTO(S)

coleoptero inseto himenoptero ecologia animal

ACESSO AO ARTIGO

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