Appropriate selection of organic hybrid sweet corn varieties can positively influence both the effectiveness of the insect biological control agent Beauveria bassiana and fungal disease resistance

Use of microorganisms to manage insect pests is a strategy compatible with organic production, but variability in their effectiveness limits the adoption by growers. Prior reports indicated that increased resistance to a fungal plant pathogen in dent maize inbreds was associated with reduced efficacy of the commercialized fungal biocontrol agent Beauveria bassiana in killing maize caterpillar pests, but this aspect has not been investigated with sweet corn. Several varieties of sweet corn certified for organic production, along with sweet corn inbreds that have been used in breeding commercial sweet corn hybrids, were evaluated for their influence on the efficacy of two commercial strains of Beauveria bassiana. As occurred in prior dent corn studies, significant differences were noted in mortality levels on day 2 for European corn borers (ranging from as much as 14.9 to 58.6%) and fall armyworms (ranging from as much as 12.1 to 46.0%) depending on the sweet corn hybrids and inbreds. Higher rates of leaf colonization by B. bassiana were associated with larger lesion sizes caused by the maize pathogen Fusarium graminearum for both hybrids and inbreds. However, greater efficacy of B. bassiana in killing insects was associated with smaller lesion sizes caused by F. graminearum for some organic production sweet corn hybrids. This information indicates it is possible to develop sweet corn varieties that are both resistant to fungal pathogens and compatible with use of B. bassiana and suggests this aspect can be further improved to promote more effective organic production of sweet corn.