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

Authors: Dowd, Patrick; Johnson, Eric

Submitted to: Organic Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2024
Publication Date: 1/22/2024
Citation: Dowd, P.F., Johnson, E.T. 2024. 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. Organic Agriculture. https://doi.org/10.1007/s13165-024-00453-w.
DOI: https://doi.org/10.1007/s13165-024-00453-w

Interpretive Summary: Organic production of sweet corn is desirable for health and environmental reasons, but the choice of materials needed to control insect pests is limited. Use of beneficial microbes to manage insect pests is compatible with organic farming but variability in their effectiveness limits their acceptance by growers. Understanding the reasons behind this variability could facilitate development of strategies to increase the acceptance rate. Different sweet corn hybrids used in organic production, and sweet corn inbreds used to develop commercial hybrids were treated with two commercial strains of the pest insect fungal disease. The sweet corn variety significantly affected the ability of the fungal disease to kill insect pests. Although past studies with dent corn inbreds indicated those inbreds with higher disease resistance interfered with the efficacy of the insect fungal disease, when one sweet corn hybrid was treated with the insect fungal disease in the present study, there was both highly effective kill of insect pests and high resistance to the sweet corn disease that was used for comparisons. This information indicates it is possible to develop sweet corn hybrids that are resistant to fungal pathogens and compatible with the use of beneficial microbes to manage insect pests. These findings provide the incentive for further development of such sweet corn hybrids for organic production that benefit both producers and consumers by enhancing safety to the consumer and the environment.

Technical Abstract: 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. Although nearly all insects died after 4 days, much greater damage was noted with those leaves that had low mortality on day 2. 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.