Management of transplant house spread of Acidovorax avenae subsp. citrulli on cucurbits with bactericidal chemicals in irrigation water.

Bacterial fruit blotch (BFB), caused by Acidovorax avenae subsp. citrulli, is a seed-borne disease of cucurbits that spreads rapidly in the warm, humid environment of the transplant house, often resulting in high numbers of infected plants going into the field. The only control options for BFB once it gets into a transplant house are crop destruction or multiple applications of a copper-containing bactericide/fungicide. In this study, various treatments were compared with the standard foliar spray application of cupric hydroxide for BFB control under transplant house conditions. Peroxyacetic acid at 80 μg/ml and ionized copper at 1.0 and 1.5 μg/ml applied through the daily irrigation water were more effective than cupric hydroxide in reducing spread of A. avenae subsp. citrulli. Combining ionized copper or peroxyacetic acid in the irrigation water with a weekly foliar application of acibenzolar-S-methyl was most effective in reducing spread. The utilization of these transplant house treatments along with the elimination of all transplants with symptoms or near plants with symptoms should greatly reduce the chances of introducing BFB into fields on transplants.