Massive production and preformulation of Metarhizium spp. for llanera locust biological control

Abstract

With the purpose to standardize the conditions to obtain a biopesticide prototype useful to the control of the llanera locust Rhammatocerus schistocercoides were established the conditions for Metarhizium spp. massive production, consisting of two methods for fungus inoculation of a substrate based in steril humid rice contained in high-density polyethylene bags which were incubated for 15 days at 25°C after inoculation. One method consisted of the utilization of a liquid preinoculum grown for two days and the other method consisted in the direct inoculation of the rice. In both cases, a suspension of 10⁶ spores/ml of the fungus was used as inoculum. The highest level of sporulation was obtained with the Last method and was expressed as 30 x 10⁸ u.f.c./g for M. anisopliae and 70 x 10'³ u.f.c./g for M. flavoviridae. Spores were separated from the substrate and obtained biomass was dried for 24 hours at 25°C. Subsecuently the compatibility between spores and different individual excipients was determined and an adherent, vegetal oil, and two solar filters (CBUVO1 and CBUVO2 ) were selected in order to obtain a product in powder. This product consisted of spores pelletized with chemical sunscreens and was designed to be reconstituted in an oil in water emulsion (0/ W) consisting of sunflower oil, Tween 80, Span 80, and water. In order to determine the effect of UV radiation against the product bare spores and pelletized spores were exposed to ultraviolet radiation under laboratory conditions at a laboratory radiation of 253,7 nm and under field conditions solar direct exposition at Puerto López, Meta. we demonstrated in both cases that excipients used to pelletize spores protected effectively the fungus against ultraviolet radiation adverse effects. Moreover, these excipients did not affect the biocontrol activity of Metarhizium spp. against llanera locust under laboratory conditions.