The following are highlights and updates about samples and questions recently received in the Plant and Insect Diagnostic Clinic. Visit the PIDC's Facebook page to ask questions and for updates and more pictures.
Tomato Mystery. The following interesting description reached our Clinic. Can you guess the problem? Garden tomatoes were not being productive and the plants looked stunted. Symptoms included yellow leaves (no spots) and with a shriveled look.
Beginner gardeners and even experienced ones may not be aware that black walnut trees close to a garden can affect the growth and productivity of many plants, but especially tomatoes. Walnut trees (including the roots) produce chemical compounds (juglone) that can be toxic to tomatoes and other plants and inhibit their growth. For a review of juglone toxicity to vegetables, trees, shrubs and perennials, see the Iowa State University Extension & Outreach Garden Column from July 11, 2005.
Oak Botryosphaeria Twig Blight is commonly observed this time of the year. The symptoms are clusters of brown, wilted leaves on the tips of branches and twig dieback extending only 4 to 6 inches inward from the tips. Photo below. Botryosphaeria Twig Blight should not be confused with oak wilt. To compare the symptoms of the two visit pages 10 for twig blight and page 12 for oak wilt on the resource “How To Recognize Common Diseases of Oaks in the Midwest” from the USDA Forest Service.
We have received rose samples that were suffering from cankers. Several fungal pathogens can be responsible for the symptoms on the stem. Common control measures include pruning affected tissue to reduce further infection and planting disease-free plants. More information on fungal cankers see the University of Illinois Report # 626, "Rose Cane Cankers."
Severe gall infestations may curl or deform leaves.
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