Response of Common Cocklebur (Xanthium strumarium) toAlternaria helianthi

A common sunflower isolate of Alternaria helianthi collected near Stoneville, MS, was pathogenic to cultivated sunflower and common cocklebur. Soybean, cotton, rice, grain sorghum, corn, wheat, and 22 other weed and crop species/varieties in nine botanical families showed no response or only minor symptoms. Therefore, further research is warranted to determine the potential of A. helianthi as a biocontrol agent against common cocklebur in geographic areas where sunflower is not a crop.