EFEITO DA INTERAÇÃO ENTRE AgMNPV E EpapGV, EM LARVAS DE Anticarsia gemmatalis.

M.E. BIEDMA; R. SALVADOR ; L. FERRELLI; V. ROMANOWSKI AND A. SCIOCCO-CAP

Recife, Brasil

Simposio; 9° SICONBIOL SIMPÓSIO DE CONTROLE BIOLÓGICO; 2005

Sociedad Entomológica de Brasil

The bean shoot borer (Epinotia aporema Wals) and the velvetbean caterpillar (Anticarsia gemmatalis Hübner) are serious pests of legume crops, in Argentina. In the main soybean area, both species are present simultaneously. Currently, they are controlled by the application of broad spectrum chemical insecticides.  Argentinean isolates of EpapGV (E. aporema Granulovirus) and AgMNPV (A. gemmatalis Nucleopolyhedrovirus) were characterized, and are being evaluated as biopesticides for management of their homologous hosts. With the aim to increase the potential use of these viruses, we have tested their interaction and the possible improvement of virulence due to the addition of boric acid in viral mixtures. The bioassays were conducted on third instars of A. gemmatalis, using the synchronous per oral technique. The LD50 value of AgMNPV was estimated at 168 OBs/larvae. Based on this result, two doses of AgMNPV were selected (300 and 50 OBs/larva) to be tested alone, in mixture with EpapGV (6000 OBs/larva), and in combination with 0.1% boric acid. Mortality was recorded daily, and viral identity in dead larvae was determined by PCR reaction using specific primers. An apparently synergistic action was observed in the viral mixtures, in which a decrease of the LT50 was also verified (i.e., 6.3 days with a dose of 300 AgMNPV OBs/larva vs. 5.4 days with 300 AgMNPV/6000 EpapGV OBs/larva). Similar results were obtained with the combination of AgMNPV- 0,1% boric acid. On the other hand, the addition of this component to the mixed viral suspension did not caused any additional increase in virulence. However, the incorporation of boric acid in this treatment significantly affected the rate of larval growth. These results suggest that EpapGV increases the virulence of AgMNPV, and the use of formulations that include both viruses, might be a valuable tool for pest management in areas with temperate climates, where E. aporema presents high incidence on legume crops and AgMNPV has a slow speed of action. Since synergistic factors (enhancins) were described in certain baculoviruses, further biological and biochemical studies will be needed in order to determine the existence of a putative enhancin in the genome of EpapGV.