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On-line version ISSN 1678-4936
J. Venom. Anim. Toxins vol. 2 n. 1 Botucatu 1996
BIOINSECTICIDE ACTION OF THE VENOM OF AFRICANIZED BEES Apis mellifera LINNAEUS 1758 (HYMENOPTERA: APIDAE): I -THE MOST SUSCEPTIBLE AGE OF Diatraea saccharalis FABRICIUS 1794 (LEPELETIER: PYRALIDAE) EGGS TO THE VENOM ACTION.
1Department of Biology, FIRP, São José do Rio Preto, São Paulo, Brazil, 2 Department of Ecology, Institute of Biosciences of Rio Claro, State of São Paulo, Brazil, 3 Department of Biology, Institute de Biosciences of Rio Claro, State of São Paulo, 4 Center for the Study of Social Insects - CEIS - UNESP, State of São Paulo, Brazil, 5 Center for the Study of Venoms and Venomous Animals - CEVAP - UNESP, State of São Paulo, Brazil, 6 Environmental Study Center - CEA - UNESP, State of São Paulo, Brazil.
ABSTRACT. The present paper aimed at testing the action of non-lyophilized venom of Africanized bees Apis mellifera through topical applications on Diatraea saccharalis egg masses. The CL50, DL50 and the most susceptible age of eggs to the venom topic application were also determined. Three-day-old eggs were the most susceptible to the venom action with CL50 equal to 8.6 mg/ml and DL50 equal to 0.173 mg/mass. The venom loses its action after being stored for 15 days.
KEY WORDS: Venom, Africanized bee, Apis mellifera, eggs, sugar-cane borer, Diatraea saccharalis.
Apis mellifera Linnaeus 1758 (Hymenoptera: Apidae) venom has been studied for its chemical features as well as its action on mammals although little is known about its action on insects (11). Piek (10) suggested that the toxins of Apis mellifera venom are of great interest of research with regard to the development of new models of biological insecticides. Different studies about the injected use of Apis mellifera venom and its products in lepidoptera and diptera larvae have been undertaken (9,11,12).
Diatraea saccharalis infestation causes direct and indirect damages to sugar cane plants. Diatraea saccharalis larvae open galleries in the sugar cane plant causing weight loss, germination faults, tipping besides allowing the penetration of the fungus Colletotrichum falcatum which causes the red rot. The fungus is responsible for the inversion of sucrose and an increase of impurities in the broth reducing the sugar and alcohol yield (7). After testing different chemical controls, Degaspari et al. (5) concluded that these were not appropriate for the control of Diatraea saccharalis eggs.
The aim of the present paper was to test the action of crude, non-lyophilized venom of Africanized bees Apis mellifera on eggs of Diatraea saccharalis and try to determine the periods of venom highest susceptibility.
MATERIAL AND METHODS
The eggs of Diatraea saccharalis were supplied by the entomology laboratory of the São João Sugar Mill of Araras, São Paulo, Brazil. The venom was obtained from Apis mellifera hives at the apiary of the Institute of Biosciences of Rio Claro, São Paulo State University, Brazil, using an electrical extractor. The non-lyophilized fresh venom was diluted in bidistilled and deionized water. Serial dilutions starting from 25.0 mg/ml of crude, non-lyophilized venom were topically applied to one, three and five-day-old egg masses of Diatraea saccharalis. Bidistilled and deionized water was topically applied to the control group. For each concentration, 15 egg masses containing approximately 28 eggs each were used and 20 µl of venom was topically applied to each mass. Then, the masses were individually conditioned in disposable Petri dishes (6.0 x 2.0 cm) and maintained in a B.O.D. incubator at 30.0 ± 0.5ºC, URA 70.0 ± 10.0% and photophase 14/10. According to Melo (8), these parameters promote embryonic development. The non-viable eggs were counted under stereoscopic microscope for 15 days, for the determination of the mortality percentage.
The corrected mortality percentage was obtained using the Abbott formula (1). The probit method was applied using the mean values to determine the CL50, DL50 and confidence intervals, according to methodology by Bliss (3,4) and Finney (6).
RESULTS AND DISCUSSION
The CL50 and DL50 values for one, three and five-day-old eggs of D. saccharalis topically treated with the crude, non-lyophilized venom of A. mellifera were 21.08, 8.67 and 31.27mg/ml for CL50 and 0.42, 0.17 and 0.63 mg/mass for DL50, respectively (Table 1). When this venom was stored for 15 days, it lost the ovicide action due to a fast degradation of its toxins in wet conditions (not shown results).
TABLE 1. Values of CL50 (mg/ml), DL50 (mg/mass) and 95% confidence intervals of for the fresh non-lyophilized venom of Africanized Apis mellifera topically applied to one, three and five-day-old eggs of Diatraea saccharalis.
The most susceptible age toward the venom was three days, probably because the embryos (caterpillars) are still in the process of development. At this stage, the venom possibly alters the physiology and behavior of the embryos. The venom in one-day-old eggs presented a DL50 value higher than that of three-day-old eggs. This was problably due to the resistance of the egg membrane, since the presence of an adhesive substance on the surface of one-day-old eggs promotes an strong attachment of the eggs to the substrate, preventing the diffusion of the venom toxins within these eggs (3). Five day-old-eggs were not much affected since the caterpillars they contain were already formed near hatching and the venom was able to penetrate into their cuticle.
The corrected mortality percentage of one, three and five-day-old eggs were 59.40, 80.91 and 46.09%, respectively (Table 2). Eggs one and three days aged were also susceptible to the action of the pathogen Metarhizium anisopliae, with a corrected mortality percentage that ranged between 79 and 100%; this pathogen have been used regularly in the biological control of D. saccharalis (2). In spite the ovicide action of honeybee venom is not very effective for one-day-old eggs, its effectivity is similar to that observed for the use of the pathogen to make non-viable the three-day-old eggs. This a promising result that makes the honeybee venom an interesting model for the development of a new class of ovicide drug towarded to the control of D. saccharalis and others insect pests with the same biological characteristics in the future.
TABLE 2. Corrected mortality percentage (Abbott) for eggs of Diatraea saccharalis, topically treated with fresh non-lyophilized venom of Africanized Apis mellifera (concentration of 25mg/ml); non-stored and stored (15 days).
The authors are grateful to Mrs. Maria Aparecida Piva, biologist at São João Sugar Mill at Araras, São Paulo, Brazil, for supplying the eggs of D. saccharalis. The present paper was undertaken with the aid of CNPq, CEIS and CEVAP.
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