Effects of dietary palm oil on nutritional indices of Diatraea saccharalis (Lepidoptera: Crambidae) for Cotesia flavipes (Hymenoptera: Braconidae) production

Abstract

Cotesia flavipes parasitizes Diatraea saccharalis, a pest that causes major losses to sugarcane production. The mass production of C. flavipes and its subsequent release onto sugarcane is one form of biological control of D. saccharalis. An essential factor for successfully fighting this pest is the development of host diets that can increase the efficiency of C. flavipes production. Palm oil contains saturated fatty acids, unsaturated fatty acids, and polyunsaturated linoleic acid. However, little is known about the effects of palm oil on C. flavipes production in the laboratory. Different concentrations of palm oil were added to the D. saccharalis diet and its nutritional indices were analyzed. Subsequently, the production and sex ratio of C. flavipes were determined. Our results indicated that the addition of higher palm oil concentrations to an artificial diet generated a high relative consumption rate (RCR) in D. saccharalis, and consequently a high relative metabolic rate (RMR), which resulted in a lower production of the parasitoid. In contrast, the lowest palm oil concentration in the artificial diet generated a low RMR and resulted in high-efficiency conversion of ingested food (ECI), enabling D. saccharalis to yield more C. flavipes. This suggests that palm oil influences the quantity of D. saccharalis ingested, which determines the number of C. flavipes that will be generated. In this study, supplementation of a D. saccharalis diet with 0.25% palm oil increased the production of C. flavipes. Therefore, this level of palm oil supplementation can aid in the production of C. flavipes on a laboratory-scale. Further research, including increasing the number of parasitoids, must be performed to mass-produce the augmentative releases of C. flavipes to manage D. saccharalis.