This article was published originally on 8/9/2013
The following are highlights and updates about samples and questions recently received in the Plant & Insect Diagnostic Clinic. Visit the PIDC’s Facebook page to ask questions and for updates and more pictures.
Now is the time cicada killer wasps scare and annoy the good citizens of Iowa. Treat the burrows in your landscape at night only if absolutely necessary (such as when the mail carrier refuses to come to your house!). Our Clinic website has a short summary. For those who want more, see Prof. Chuck Holliday's fascinating page.
Strawberry Root Weevils continue to appear indoors. This common accidental invader is shiny black, light bulb-shaped and slightly longer than 3/16 inch. They are a temporary nuisance. Sweep up and discard. More on the Clinic website.
Earwigs are scavengers found in any damp, sheltered location, including under mulch and litter on the ground and under the loose bark of dead trees. Earwigs do not attack and feed on trees and are incapable of tunneling into or feeding on wood. However, earwigs are commonly found inside hollow trees and in tree wounds were there is moisture. They are taking advantage of an existing condition and not the cause of any tree injury or decline.
We are getting several red and bur oak trees that tested positive for oak wilt and a maple sample tested positive for Verticillium wilt. We are also starting to see bur oak blight symptoms, including the characteristic petiole necrosis (see picture below). We are still seeing a lot of apple scab on apple and crabapple and also rust. We’ve also had a hosta with what appears to be hosta petiole rot.
Bur oak blight (BOB) petiole necrosis. Photo credit: D. McNew