Fishing spiders have been on the move the past week! They are a large noticeable type of spider and a bit intimidating especially for those who are not fans of spiders. Luckily fishing spiders are completely harmless.
With all the rain, diseases are flourishing!
The clinic has received several of oak samples. It seems this is a harsh year for oaks. We received samples that were positive for Bur oak blight
and Tubakia leaf
We also received samples of oak trees suffering iron deficiency
and oak decline. Multiple factors can contribute to oak decline including environmental stress such drought, frost, diseases and pests. For more information visit the USDA Forest Service resource on oak decline.
Elm black leaf spot and anthracnose. These two diseases are common fungal diseases of elm leaves. Anthracnose tends to be worse in years with wet spring weather. Anthracnose is caused by several fungal pathogens and is primarily a cosmetic disease. It causes leaves to look unsightly and sometimes drop. Raking and removing fallen leaves can reduce the pathogen numbers. See the photo below.
We received several apple, crabapple and pear samples with symptoms of fire blight and bacterial blast. Symptoms may include blossom blight, wilting and browning of shoot tips (shaped like a shepherd’s crook), and stem cankers. It is important to confirm the disease as other abiotic factors can cause similar symptoms. Once confirmed, manage fire blight by thoroughly pruning infected limbs (blighted shoots and cankered limbs) as soon as symptoms are detected and before extensive necrosis develops. Sterilize pruning tools between every cut with alcohol or household bleach. Read more about pruning in ISU Extension & Outreach pamphlet PM0780
, available online. Prune infected branches well below the infected area. For more information about fire blight, please visit the Plant & Insect Diagnostic Clinic website
Common samples inlcude solanaceous vegetables (potatoes and tomatoes) with herbicide injury. For more information read the article "Chemical injury in vegetables
With all the rain and moisture mushrooms
and slime molds are also thriving. Our curiosity of the week is a slime mold commonly known as "dog vomit slime mold." This is a Myxomycete (not a true fungus) that grows on mulch. For more interesting facts see the University of Wisconsin Botany website