2012 Annual Report
1a.Objectives (from AD-416):
The objectives of this research are to test, in the laboratory and in the field, the efficacy of selected biological agents for the selective control of cacao diseases, specifically, Moniliophthora roreri and Moniliophthora perniciosa. The research will focus on endophytic Trichoderma spp. native to Ecuador that were previously identified as having biocontrol potential, but other agents such as Bacillus species may be considered. The development of biocontrol formulations with enhanced disease control efficacy in the field is of special interest. Little is known about how biocontrol formulations influence the establishment and efficacy of endophytic agents in tropical ecosystems, especially as applied to trees such as Theobroma cacao (cacao). The economic sustainability of optimized biocontrol strategies will be determined in order to demonstrate biocontrol’s merit as a “best practice” for cacao farmers.
1b.Approach (from AD-416):
Candidate endophytes (Trichoderma species) have been screened to demonstrate their ability to colonize cacao and for biocontrol efficacy against cacao pathogens. At present, isolates to be considered for further study include 15 isolates previously screened for biocontrol and endophytic efficacy in cacao by ARS, and several isolates of specific interest to INIAP scientists. Four Bacillus isolates previously collected in Ecuador and screened by collaborators for biocontrol and endophytic activity in cacao may also be considered. The capacity of different formulations to enhance biocontrol efficacy will be determined. The formulations used to date in biocontrol research in cacao have incorporated starches (as carriers), surfactants, or water alone. Lab-based research on formulations with Trichoderma isolates indicate a significant benefit to Trichoderma efficacy in response to added nutrients, humectants, and vegetable oils (corn oil). Initially, these formulations (including nutrients, humectants, and oils) will be evaluated for their abilities to enhance Trichoderma biocontrol efficacy in small scale and short term field studies. Formulation concepts will be optimized as to specific components (for example, readily available nutrient sources), concentrations, and application timing. Standard protocols will be developed for rapid evaluation of biocontrol agents, formulations, and their interactions in the field. In collaboration with cooperating institutions, large scale field trials of promising endophyte formulations with biocontrol potential will be conducted. The economic impact of biocontrol strategies for the control of disease will be determined.
The best cultural practices, integrated pest management (IPM) practices, and cacao clonal material selected for disease resistance and yield will be evaluated. The first three treatment combinations will include control (no management), best cultural practices, best cultural and IPM practices combined, and best cultural and IPM practices combined with superior cacao clonal material. The fourth treatment involves rejuvenation of cacao trees by topping and grafting. Regrowth from the top of cacao tree stumps will be grafted with selected superior hybrid national cacao clones. Twenty-five percent of the trees within the selected plots will be rejuvenated every year.
When used in invert oil formulations, corn oil greatly enhances pod colonization by Trichoderma and greatly reduces frosty pod rot of cacao. Unfortunately corn oil is expensive where cacao is grown in South and Central America. We are attempting to identify lower cost vegetable oils as replacements for corn oil. Initial field studies were carried out assessing the impact of vegetable oils (soybean oil, palm oil, and sunflower oil) on cacao pod colonization by Trichoderma when used in invert oil emulsions. Results to date suggest palm oil and sunflower oil are effective replacements for corn oil and both are of lower cost and greater availability than corn oil in cacao growing areas. Plans have been formalized for studying the impact of low volume applications of invert oil formulation carrying Trichoderma for management of cacao diseases. Low volume applications would further reduce the cost of application if effective in managing disease.