Anthracnose of sweet basil (Ocimum basilicum) caused by Colletotrichum sp. This disease affects both leaves and stems. Image courtesy of Dr. Gordon Holcomb, Louisiana State University. Fusarium wilt of sweet basil, caused by Fusarium oxysporum f. sp. basilici, was first reported in Louisiana in 1994. Symptoms include chlorosis, wilt, leaf drop, vascular discoloration and plant death. Although typically a soil-borne pathogen, F. oxysporum f. sp. basilici may also be transmitted through infected seed. Image courtesy of Dr. Gordon Holcomb, Louisiana State University. Bacterial leaf spot of basil casued by Pseudomonas cichorii. Gray to black, water-soaked, necrotic spots commonly develop along the leaf margins. Image courtesy of Dr. Gordon Holcomb, Louisiana State University.

Black spot of basil caused by Colletotrichum sp. Image courtesy of Dr. Gordon Holcomb, Louisiana State University. Tomato spotted wilt virus (TSWV), which is transmitted by thrips, was first observed on basil in 1998. Symptoms may include ring spots (as seen here), leaf distortion and severe mosaic. Image courtesy of Dr. Gordon Holcomb, Louisiana State University.