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It's that time of year when landscapers and homeowners bring in oak leaves and leaves from other hardwoods such as maple and elm with scorched edges, to be tested for bacterial leaf scorch. Currently, there is a $20 charge per sample for bacterial leaf scorch (BLS) testing. For BLS testing, at least 20 leaves are required and the test may take up to two weeks to run. Check payable to University of Delaware.
Due to similarity of symptoms to other environmental and cultural disorders, a confirmation diagnosis is based on detection of bacteria in plant tissue. A laboratory test necessary to detect presence of causal bacteria relies on sampling approximately 15-20 petioles of leaves. Attached leaves provide the best specimens, for leaves collected in September. A positive detection of bacteria along with dieback indicates the tree in question will survive only a few years. Severely affected trees should be removed to reduce spread to nearby trees. The bacteria that cause BLS are not harmful to humans or animals.
Checks payable to University of Delaware, $20 per sample. Please indicate on the form that BLS testing is requested.  Delaware Cooperative Extension office staff may receive plant samples in the County Offices.
NFG August 2019

A new fact sheet from UD Cooperative Extension highlights information on bacterial leaf scorch (BLS) of oak and other trees.  BLS has been problematic in oaks in the red oak group for almost ten years, and has led to the decline and death of many oaks in Delaware.