Researchers have uncovered a fascinating interplay between the defenses that help sweet corn resist fungal diseases and the effectiveness of a beneficial fungus, Beauveria bassiana, in controlling caterpillar pests. This discovery could have significant implications for organic growers who rely on sustainable pest management strategies. The findings suggest that the right combination of genes in certain sweet corn varieties can strike a balance between disease resistance and compatibility with the biocontrol agent, offering a promising path forward for optimizing crop protection.
Balancing The Scales
Entomologist Pat Dowd and Molecular Biologists Eric Johnson at the ARS National Center for Agricultural Utilization Research are leading a research team looking into how sweet corn defenses interact with the mode of action of the beneficial fungus Beauveria bassiana.
In previous work with field (dent) corn, it was observed that resistance to Fusarium disease can mitigate the activity of Beauveria as a biopesticide against Lepidopteran caterpillar pests such as the European corn borer and the fall armyworm. The researchers did find that not all Fusarium-resistant dent corn lines had lower performance as insecticides, however, suggesting the potential for an optimal genetic combination to provide both disease resistance and fungicide compatibility with Beauveria.
Solving the Sweet Corn Puzzle
The follow-up studies with sweet corn demonstrate an equally intriguing pattern. Beauveria killed 12 to 58 percent of the targeted caterpillars when applied as a biopesticide, depending on the specific sweet corn line tested. Resistance to disease, indicated by smaller necrotic spots on Fusarium-infected leaves for example, was correlated in some lines with more frequent mortality after caterpillars encountered fungus spores. On the opposite end of the scale, sweet corns that scored less well for disease resistance were associated with larger dead spots providing less good pest control.
The effectiveness of these Beauveria strains also differed, suggesting that more research is needed to turn these laboralatory differences into practical recommendations for growers.
Hitting Home for Organic Growers
These findings are especially relevant for organic growers, who have fewer chemical controls available to them than are present in conventional production systems. Solving the riddle, farmers there say, would be identifying a sweet corn variety that is not only resistant to Fusarium, but also delivers sufficiently high levels of Beauveria Sect.
Encouraging findings came, for example, from recent gene expression studies comparing sweet corn hybrids that differed in their respective combinations of resistance against Fusarium and efficacy of Beauveria conducted by the researchers. This can ultimately inform selection for sweet corn varieties that can balance these factors, allowing organic growers to benefit from natural defenses and biocontrol agents harnessed to maintain sustainable crop protection.
