CLM and Canker: Dangerous Summer Duo

Ernie Neff Diseases, Pests

Citrus canker lesions in leafminer galleries. (Photo by UF/IFAS)

Chris Oswalt details the connection between citrus leafminer (CLM) and citrus canker in the May/June Central Florida citrus Extension newsletter, Citrus from the Ridge to the Valley. He also offers some management tips.

“I don’t think we can overstate the effect of leafminer damage on citrus foliage and the increased development of citrus canker lesions on damaged leaves,” the multi-county citrus Extension agent writes.

CLM doesn’t transmit citrus canker, but foliar damage caused by CLM “allows for significant increases in canker inoculum,” Oswalt states. He explains that CLM mines open citrus leaves to disease infection for extended periods. The summer rainy season is a bad time for an increase in inoculum because conditions are favorable for canker proliferation and subsequent infection, he adds.

Oswalt cites a U.S. Department of Agriculture study that showed five times more canker lesions in young trees without CLM control than in trees with CLM control. In a mature grove, blocks of grapefruit and lemons surveyed in July and August had an average of 79% of leaves with canker lesions directly associated with CLM damage.

To minimize the potential for fruit and foliage infection, pesticide applications need to be timed to significantly reduce CLM populations during the summer and early fall, Oswalt writes. “The primary window of opportunity to control CLM is 13 days after bud break of a new flush to 31 days after this bud break,” he states. “Experience shows that this is much easier to do for the spring flush but becomes increasingly difficult as seasonal flushes continue through the growing season (summer and fall).”

Oswalt is the University of Florida Institute of Food and Agricultural Sciences citrus Extension agent for Hillsborough and Polk counties.

Learn more about citrus leafminer control and citrus canker management.

Source: University of Florida Institute of Food and Agricultural Sciences

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