Patogenicidade de fungos do gênero Isaria (Persoon) sobre Coptotermes gestroi (Wasmann) (Isoptera : Rhinotermitidae) e aspectos imunológicos

Abstract

The termite Coptotermes gestroi (Wasmann) is an urban and agricultural pest that has been established in many areas of the world. The use of entomopathogenic fungi is an option to minimize the economic loss caused by this termite. It is known, however, that physiological disorders caused by a pathogen trigger defence reactions of the insects, such as humoral and cellular responses (hemocytes). Thus, this research had as objectives: 1. to verify the pathogenicity of Isaria farinosa and I. fumosorosea to the termite C. gestroi and 2. to qualify and quantify the hemocytes in workers of this insect challenged by the pathogenic and virulent isolates. All fungi isolates tested, in the concentration of 107 conidia mL-1, were pathogenic and virulent causing more than 60% mortality, with an average survival of 2.0 to 3.9 days. However, the isolate URM-4995 of I. farinosa was one of the most virulent, being selected for the LC50 determination, estimated at 6.7 x 105 conidia mL-1, and to study the cellular immune response.The total average of hemocytes found in the hemolymph of workers termites treated with that isolate, in the concentration of 107 conidia mL-1, was not different from the hemocytes average recorded for the control, within 12, 24, 36 and 48 hours intervals. Regarding the cell types, the analysis in light microscopy revealed that the most frequent cells were plasmatocytes. The differential counts in infected and uninfected insects, did not differ significantly within the timeintervals assessed, there was only a change in function of time for plasmatocytes and prohemocytes. Thus, the results of total and differential counts show that I. farinosa in the concentration 107 conidia mL-1, did not affect quantitatively and qualitatively in the number of hemocytes of C. gestroi and that this pathogen appears as a promising candidate for controllingthis insect.