Analise do efeito da radiação de microondas sobre Anagasta Kuhniella Zeller (1879) (Lepidoptera: Pyralidae) e seus dois agentes de controle biologico, Bracon hebertor (Say, 1836) (Hymenoptera: Braconidae) e Bacillus thuringiensis var. kurstaki (H:3a3b)

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

The application of Integrated Pest Management (IPM) means the utilization of efficient control methods which are ecologically safe and economicaly viable. Therefore, it is extremaly important to gather more information about the possible interactions between the different control agents, aimimg to optimize such a method. Microwaves (300 a 300.000 MHz), as well as Bacillus thuringiensis and the ectoparasitoid Bracon hebetor (Say, 1836) are being studied individually by some institutions, as promissing control agents of some stored product pests. The present work was developed to study and evaluate the relations among the parasite Bracon hebetor, his natural host, Anagasta kühniella Zeller (1879), the entomopathogen Bacillus thuringiensis varo kurstaki (H- 3a:3b) and microwaves radiation. The mother culture of the pyralid and braconid species were initiated from live material collected from flour mills in Campinas municipality, state of São Paulo. The cultures were maintained and experiments were realized under controlled laboratory condítions of 25 :t 2° C, 60 :t 10 % R.H. and 12 hours of photoperiod. To evaluate the tolerance of B. thuringiensis to microwave radiation samples of the commercial product Dipel (Abbot) were utilized. This product contains 16,000 IUI mg and formulated as a wettable powder. The radiation treatments were undertaken utilizing the maximum potency of a domestic Panasonic microwave oven (NN 7954 BH/K, 2450 MHz). The mortality rate among the different developmental stages of the two insect species was observed to be positively related with the radiation exposure time. Among the Anagasta kühniella developmental stages, while the last instar larvae showed to be more sensitive to radiation (median letal exposure time, LET 50 = 15,63 s), the egg stage showed to be more resistant (LETso= 121,67 s). The third instar larvae, as well the adult stage, revealed a moderate sensitivity (LETso= 19,34 s and 22,61 s, respectively). Within the egg stage of Anagasta kühniella the full grow embryo showed to be more sensitive than newly deposited eggs. The impact of the direct exposition to microwaves on the full grow Anagasta kühniella larvae (LET so= 15,63 s) did not differ when compared with those larvae imbeded in their natural diet, whole wheat flour (LETso = 16,28 s). The sequence and intensity of the external symptoms, showed to be directly related to the duration time in which larvae of Anagasta kühniella were exposed to the microwave radiation. Letargy and locomotion desfunctions were the initial alterations. Dehydration and body wall darkening , reaching dark brown, were observed before death. The radiation also showed to be harmful to the adult stage of the same pyralidae species, reducing longevity as well as reproductive capacity. Bracon hebetor adults showed to be more resistant to radiation (LETso ::: 106,57 s) when compared to Anagasta kühniella adults (LETso = 22,61 s) and larvae (LET50 = 15,63 s). Samples of Bacillus thuringiensis var kurstaki were exposed to different times of microwaves radiation (2450 MHz) and were ofered to third instar larvae of Anagasta kühniella in three different concentrations (0.02 %, 0.2% and 2.6%). This electromagnetic wave did not present any interference in the patogenicity of the entomopathogen in the extrem concentrations (0.02 and 2.6%). However, in the 0.2% concentration, next to LCso of the larvae, the patogenicity of Bacillus thuringiensis was altered by the time of exposure to the radiation. Finally, radiation by microwaves could be considered as a promissing method, efficient and compatible with biological control ones, to participate in IPM programs of the Mediterranean Flour Moth, Anagasta kühniella

ASSUNTO(S)

bacillus thuringiensis bacillus thuringiensis - efeito da radiação controle biologico

ACESSO AO ARTIGO

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