IRREGULAR LEAF SPOT

Irregular (or funky) leaf spot

[Unknown causal agent]

Irregular (or funky) leaf spot is a problem of unknown cause. Symptoms appear early in the growing season on lower leaves. Lesions look like early leaf spot, but spores are never observed. Lesions are scattered over the leaf surface. Some defoliation may occur, but yield losses have not been demonstrated. Fungicides do not control irregular leaf spot. Apparent failures in leaf spot control within 45 days of planting are probably due to irregular leaf spot or phytotoxicity. Confirm the presence of early leaf spot before making unplanned fungicide applications early in the season (prior to R3). Contact your county agent for a positive diagnosis.

Phytotoxicity (chemical toxicity) caused by systemic insecticides applied at planting can be confused with leaf spots. Spots caused by phytotoxicity usually are found around the margins of the lower-most leaflets and generally are found before mid-June. Herbicides can also cause spots by burning areas contacted by spray droplets. Affected areas lack fungal structures and spores. Phytotoxicity symptoms tend to be distributed regularly (such as at the ends of rows) or uniformly over the field. Learn to distinguish between symptoms associated with chemical damage and foliar diseases. Avoid practices that lead to plant injury.

Publication Copyright Information:

© North Carolina State University & Virginia Tech University. 2010.  Prepared by Barbara Shew, Bridget Lassiter, and Gail Wilkerson [Departments of Plant Pathology and Crop Science, North Carolina State University, Raleigh, NC] and Pat Phipps [Tidewater Research Station, Virginia Polytechnic Institute and State University, Suffolk VA]. Additional pictures provided by Joyce Hollowell, Brian Royals, Damon Smith, and Brenda Watson.

Text taken from the 2010 NC Peanut Information Guide, (AG 331), North Carolina Cooperative Extension Service, and the 2010 Virginia Peanut Production Guide, (432-101), Communications and Marketing, VPI. 

This publication was made possible through a Crops at Risk (CAR) grant administered by the United States Department of Agriculture (USDA).