Stewart's Wilt - Disease Cycle

Disease Cycle

Chaetocnema pulicaria, the primary vector for Pantoea stewartii, overwinter as adults and will begin feeding on corn seedlings early in the spring season. The bacterium overwinters in the gut of the adult corn flea beetles. Warmer winter temperatures will allow for greater beetle survival and in effect, higher populations come spring. Emerging beetles in the spring transmit the bacteria into corn leaf tissue through feeding. The corn flea beetles wound the leaf and contaminate the wounds with insect frass (excrement), which additionally contains the bacteria. Once the bacteria are inside the plant, they multiply and fill the xylem and intercellular spaces of the leaf. The degree of multiplication is highly dependent on susceptibility of the cultivar. Highly susceptible plants become systemically infected and face symptoms such as stunting, wilting, and even death. In less severe cases, a plant may show leaf lesions that are long and irregularly shaped. Some genotypes are able to greatly restrict pathogenic growth. In such plants, the leaf lesions are short, insignificant may even be non-existent. In certain corn varieties, kernels can be infected later in the growing season after flowering occurs. Although corn kernels can be a source of inoculum, seed transmission is quite rare.