Evaluation of oil and water formulations of the fungus Beauveria bassiana (Balsamo) Vuillemin in the field

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, CENICAFE, 1400 m.s.n.m.), spraying of the fungus: Bb in water (10 ml of oil for agricultural use, in 20 It of water) and Bb in tersol oil (10% of oil formulation of the fungus in water, plus the emulsifier agent: 500 ml/ 100 It of formulation) was carried out. The sun and shadow plots (12 for each condi­tion) were randomly selected six to the water preparation, and six to the oil formu­lation of the fungus. Plots of 50 trees with the borders were selected, for a total nurn­ber of 30 branches and 120 coffee berries per branch (experimental unit). The sprayings were made with a low volume "Ulvafan", with a nozzle with a flux of 70ccimin. The spraying volume per branch was 17,5 ml, with a dose of 4,02 x 10⁹ conidia. The spraying was directed to the upper and lower side of the branch. The viability of the fungus Bb on the selected ber­ries was evaluated at different times (0, 2, 4, 5, 24, 48, and 336 h) of exposure of the preparations to the climatic 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 of 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 viability of the treatments was 45,97%. Recovery of the fungus B. bassiana in the evaluated times was registered for all the 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 potential to control the coffee berry borer Hypo­thenemus hampei.