There have been no new reports of late blight in New Jersey this past week. Late blight was reported in Northeast OH, Western NY and Lancaster, PA this past week. The extremely hot, dry weather this week throughout NJ has most likely reduced the immediate threat of late blight, but growers should remain cautious because the pathogen could reappear anytime weather conditions favor its development (There is a threat of rainfall everyday this coming week).
The most recent samples from tomato and potato from Salem County sent to Cornell for identification show that P. infestans was positively identified on one of the four samples submitted. The sample was identified as US-23 which is mefenoxam sensitive. The sample from Mercer County earlier in the season was also indentified as US-23 and also mefenoxam sensitive. The 3 other samples from Salem County were identified as potential Phytophthora’s, but what species they are still needs to be determined. A new sample from processing tomato was sent to the Plant Diagnostic Lab at Rutgers this past week. Symptoms appearing on processing tomatoes include infections that appear to take place mostly in the crotch of branches that later extend into the stem as an very irregular black lesion that sometimes griddles the branch resulting in the wilting and death of affected branches. The diagnostic lab also tentatively identified this as a Phytophthora using an ELISA test. More work is currently being done to determine the species. If you suspect Late blight on your farm please contact your county agent.
