Investigations in Georgia, USSR, showed the importance of the combined effect of the gut-specific nuclear polyhedrosis Birdiavirus diprionis and the parasitoids Drino inconspicua and Exenterus abruptorius in natural control of Diprion pini on pine [Pinus], with much of the mortality of over 90% among larvae brought to the laboratory apparently being due to the presence of the virus alone or to the appearance of a latent form of it triggered by other factors, notably the parasitoids; these are not themselves attacked. When, in control experiments, Gomelin [Bacillus thuringiensis] was applied at 3OX I IV spores/g and 2 g/ha with a 25% Dimilin [diflubenzuron) w.p. at 5 g/ha (a sublethal dose) against chiefly 2nd-instar larvae, mortality reached 89.5%. none