Plant and Insect Diagnostic Clinic Update - July 13, 2011

The following are highlights and updates about samples and questions recently received in the Plant & Insect Diagnostic Clinic:


Diseases


We are still getting quite a bit of samples and consults about conifers with needle browning and needle drop (many of them due to environmental stress). We also had a spruce and white pine injured by herbicide, most likely due to Imprelis (see this New York Times Article). On the fruit and veggie side, we’ve received strawberry samples with leaf spot and leaf scorch and some cherries with leaf spots and gummosis. We are also beginning to see Septoria leaf spot on tomatoes and bacterial wilt on cukes and muskmelons.


It is the time of year when oak wilt symptoms would begin to show on oak leaves.  Symptoms are the browning of leaves on an entire branch. To test for oak wilt we need several branches about 1/2 inch in diameter.  Please see our pamphlet on Oak Wilt for more information.


Verticillium wilt is a very different wilt disease whose symptoms would also be appearing now.  Symtoms consist of wilting or browning leaves on a branch.  Verticillium wilt affects many species of trees and plants including maple, ash, lilac.  For more information please see our pamphlet Verticillium Wilt of Woody Plants.


Insects


Iowans have been out and about in the woods collecting ticks.  In Iowa we have three common tick species, the lone star tick, the American dog tick, and the Black-legged tick (aka the deer tick).  The black-legged tick is the only species known to carry lyme disease in Iowa. Other species rarely carry disease, but it is always important ot let your doctor know if you become ill and had a tick attacked for 24-36 hours.  Ticks take a long time to become attached and feed.  To reduce the chances of any disease transmission it is important to check yourself for ticks after returning from outside and to remove them promptly by pulling them out with a pair of tweezers.  Do not use alcohol or other substances on the tick.  Agitating the tick could potentially lead to a greater chance of disease transmission.  For more information on ticks please see Ticks and Tick-borne diseases in Iowa.


Bagworm activity has been reported in southern Iowa and in Clive (Polk County).  Reporters indicated the silken bags made from bits of plant debris as the caterpillar is feeding on the foliage are already one-half to five-eights inch long.  Now is the time to check and treat if bagworms are found.  See the April, 2010, Horticulture &Home Pest Newsletter for more information and control options.


The annual cicadas are buzzing in the trees in late afternoon, and the cicada killer wasps are right behind and right on schedule.  See our website for more information on how to treat these large, frightening, but non-aggressive digger wasps.  Treat the ones you can't ignore!


Have you seen honey bee swarms?  If so, you know it's quite a spectacle, but the prudent thing to do is watch from a safe distance and wait for them to move on, which usually takes only a day or two.  Kill the swarm with soapy water spray only if you must.  A neighberhood beekeeper may take the swarm, though not all beekeepers are interested in having and hiving wild bees, so don't "bee" offended if your offer is turned down!

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