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.
As is typical of most springs, this has been a good year for larder beetles. An entomologist would say these scavengers are harmless but annoying. A homeowner would say they are disgusting. Larder beetle control is difficult because the beetles and larvae originate inside attics and wall voids where they feed on dead animals such as insects, squirrels and birds. See the photo below on more information on the Clinic website.
Leafcurl ash aphid disfigures the terminal leaflets of ash foliage but does not cause significant harm to otherwise healthy trees. Prune off deformed leaflets you can safely reach and ignore the rest! More.
What could pass for "egg-like spheres" on silver maple leaves are actually leaf deformations called maple bladder galls. See the photo below. Leaf galls are not damaging to otherwise healthy trees though premature leafdrop may occur. Galls cannot be cured after they have formed and prevention is not practical. Maple bladder galls appear on newly-emerging leaves throughout early summer. New galls are red and eventually turn black.
Several recent samples have been vegetable seedlings grown in the greenhouse or in high tunnels with nutritional problems. Diseases have not been an issue - yet - but plants grown in suboptimal conditions can be weakened and may become prone to diseases.
Recent wet spring weather is causing several diseases to pop up. In apples and pears we have received several samples of apple scab and fire blight. Fire blight is a problem in susceptible varieties of pears and apples. This is a difficult disease to manage. The most important tactic is to plant resistant varieties. When plating new trees, check the list of fruit tree cultivars with resistance to fire blight recommended in Iowa State University Extension & Outreach Bulletin PM453, "Fruit Cultivars for Iowa."
We continue to observe powdery mildew in herbaceous perennials and turf. Powdery mildew is a common fungal disease found on a wide range of plants, causing cosmetic damage but would not result in plant death. Avoid shady areas and increase the air flow throughout the canopy to help reduce the incidence of powdery mildew. The powdery mildew pathogen will overwinter in associated plant debris. Consider removing and destroying symptomatic plant parts this summer and in the fall remove plant debris. Both measures can help reduce the amount of the pathogen present for the next year. See more about garden sanitation in the Horticulture & Home Pest Newsletter from April 24, 2015. Select and plant resistant or tolerant varieties when available. See Purdue University bulletin ID-414-W, Disease-Resistant Annuals and Perennials in the Landscape.
Turf diseases are very common under rainy conditions. Avoid adding unnecessary irrigation to lawns as excessive moisture is already exacerbating turf diseases this season.
Oak samples remain common. Most of the samples are showing symptoms of oak tatters. See article elsewhere in this issue.
Maple bladder galls are deformations of emerging leaf tissue caused by the presence of a tiny mite.