Evaluation of Entomopathogenic Fungi and Entomophagous Nematodes for the Control of White Grub (Coleoptera: Scarabaeidae) in Broccoli Fields in Guatemala
Albaro Orellana Polanco, Humberto Carranza Bazini (Guatemala); Stephen Weller (US)
From July to November 1997 two test sites were established in Chimaltenango and Jalapa with the objective of determining which isolates and/or commercial products based in enthomopathogenic fungi and entomophagous nematodes are effective biocontrols of white grubs (Phyllophaga sp. and Anomala sp.) in broccoli. In a completely randomized experimental design with three replications, three isolates of the fungus Metarhizium anisopliae, one of Beauveria bassiana, and one each of the nematodes Steinernema and Diplogasteritus were evaluated. The chemical control was Imidacloprid and a zero control check plot was also included. The variables measured were plant populations affected by white grub at 15, 30, 45 and 60 days after transplant (dat), commercial and reject yield (kg/ha). An individual site analysis of variance test was done, as well as a combined site ANOVA and the Duncan multiple mean comparison test.
The objective of this study was to determine which isolates and/or commercial products based in enthomopathogenic fungi and entomophagous nematodes are effective biocontrols of whte grus in broccoli in Guatemala.
The individual ANOVA indicated that no statistical differences existed between treatments at Jalapa, but there were differences at Chimaltenango. In Jalapa, damage at the last reading (60 dat) varied from 22% in the chemical control Imidacloprid to 79% in the zero check. In Chimaltenango Imidacloprid treated plants had the least amount of damage at 15, 30, 45 and 60 dat (2% of damaged plants at 60 dat). The combined ANOVA indicated significant differences exist at the sites and in treatments. Damage observed at Jalapa was worse than at Chimaltenango, reaching a maximum of 66% and 21% respectively, at 60 dat. In conclusion, Imidacloprid was superior to the fungi isolates and nematodes. In the commercial yields of both sites (Jalapa and Chimaltenango) significant differences were found. The highest yield was obtained with the chemical treatment (Imidacloprid) with 11,717 and 14,387 kg/ha at Jalapa and Chimaltenango, respectively.