Field evaluation of oil formulations of the fungus Beauveria bassiana (Bals.) Vuill

Abstract

In an attempt to evaluate the viability of the fungus Beauveria bassiana (Bb-9205) on the coffee ecosystem, under sunlight and artificial shadow (Naranjal Central Station, Cenicafé, 1,400 masl), spraying of the fungus Bb in water (10 ml of oil for agricultural) use, in 20 1 of water) and Bb in Tersol oil (10% of oil formulation of the fungus in water, plus the emulsifier agent: 500 m1/1001 of formulation) was carried out. The sun and shadow plots (12 for each condition) were randomly se­lected, six for the water preparation, and six for the oil formulation of the fungus. Plots of 50 trees with the borders were selected, for a total number of 30 branches and 120 coffee berries per branch (experimental unit). The sprayings were made with a low volume "Ulvafan" sprayer, with a nozzle with a flux of 70 c/min. The spraying volume per branch was 17.5 ml, with a dose of 4.02 x 10⁹ conidia/ branch. The spraying was directed to the up­per and lower side of the branches. The vi­ability of the fungus Bb, on the selected ber­ries, was evaluated at different times (0, 2, 4, 5, 24, 48, and 336 hours) of exposure of the preparations to the luminosity factors. The es­timation was made by the method of culture of successive dilutions of the initial sample (120 berries in 30 ml of 10% glycerol) on the surface of a selective medium for the isolate of B. bassiana. The treatments were evalu­ated under simple classification design with a factorial arrange 2x2 (two luminosity con­ditions, sun and artificial shadow, and two preparations on the fungus, oil, and water). In order to measure the response of the treat­ments, the variable relative ratio of reduction 01 the viability of the fungus Bb-9205 in each treatment was evaluated, and the selected treatment was that with the lower relative ra­tio, which had the lower reduction of the vi­ability throughout time. The analysis of the results did not show any difference between treatments under sun and shadow, neither the interaction preparation-luminosity condition. The mean value of the relative ratio of reduc­tion of the viability of the treatments was 45.97%. Recovery of the fungus B. bassiana in the evaluated times was registered for all treat­ments. The response shows the persistence of both preparations of the fungus B. bassiana (oil and water) on the coffee ecosystem, un­der sun and shadow conditions, throughout the time of evaluation and its biological po­tenti al to control the coffee berry borer Hypothenemus hampei.