OCCURRENCE OF COLLETOTRICHUM-GLOEOSPORIOIDES ON POKEWEED AND SICKLEPOD STEMS IN GEORGIA AND PATHOGENICITY ON BLACK LOCUST

Pokeweed (Phytolacca americana) and sickle pod (Cassia obtusifolia), w eeds occurring in a black locust (Robinia pseudoacacia) progeny test p lantation in Greene County, Georgia, USA, were evaluated as possible r eservoirs of inoculum of Colletotrichum gloeosporioides. C. gloeospori oides was recovered from 80% of pokeweed stems and 90% of sicklepod st ems assayed in December 1994, from 100% of pokeweed stems collected in December 1994 but assayed in January 1995, and from 47% of pokeweed s tems assayed in July 1995. Three weeks after inoculation with C. gloeo sporioides, plus 15 days after detached stems were treated with the he rbicide glufosinate to accelerate tissue senescence, acervuli were pro duced on 26 of 28 pokeweed stems. Acervuli covered an average of 28% o f the surface area of 2-cm stem sections. An isolate of C. gloeosporio ides obtained from pokeweed was as virulent on black locust as an isol ate from black locust. C. gloeosporioides which infects black locust m ay form latent infections in pokeweed that may have epidemiological si gnificance.