Indiana Department of Natural Resources sent this bulletin at 08/13/2019 12:33 PM EDT
Weekly Review for Aug. 13, 2019
This informal report by the Division of Entomology and Plant Pathology is designed to update the Nursery and Greenhouse industry of insect and disease pests the Division has been encountering on a week to week basis and as a way to give a “heads up” of things to be on the lookout for. Comments and questions about this report are welcome and can be sent to your respective Inspector.
A few weeks ago, I wrote about forsythia with symptoms that looked a lot like fire blight. Well, Purdue’s PPDL identified it as Phytophthora causing both stem dieback and root rot. This nursery irrigates from catch ponds and is a location where I used to find Phytophthora on Rhododendron regularly until they switched up their watering techniques. The lab is still working to ID the species. Curiously, Ken Cote was telling me about a case of “Fire Blight” on flowering pears that also turned out to be Phytophthora. Just goes to show how difficult field diagnostics can be.
At a nursery in Elkhart County, I was finding a lot of white, sticky masses on the trunks of redbuds. Two-marked treehopper egg masses match up pretty well. (A shout-out to Joe Boggs and the Buckeye Yard & Garden onLine blog!) The curious thing was I kept finding aphids sitting on the egg masses. Could this be due to the drought? While I can’t recall ever finding adult treehoppers at this nursery, with the number of redbuds scattered around the property, it doesn’t surprise me. Something to keep an eye out for the future.
Other finds this week include the heaviest cedar apple rust on crabapples I’ve ever seen, oak slug sawfly injury on red oaks, and spider mite starting to become a problem on maples, serviceberry, and some oaks. However, a bit of much needed rainfall today might help mitigate the spider mite issues.
I managed to get some nurseries inspected in LaPorte County last week. Tar spot seems to be more scattered this year but where it is present it is pretty heavy, especially on the red-leafed Norway maples. Apple scab was present on crabapples and Amelanchier. Powdery mildew was present on the usual suspects such as rose, phlox, lilac and magnolia. At one Nursery, I found a large population of Tulip Tree Scale in Tulip tree. As I pulled in, I noticed the Tulip trees were black from the honeydew! Other insects I noticed included Oak Slug Sawfly, Oak Lacebug, Oak Apple Gall and Hedgehog Gall. Some Autumn Blaze Maple and Red Sunset Maple had Maple mites.
A couple weeks ago, I attended the Hemlock Woolly Adelaida Managers Meeting. While this pest isn’t in Indiana it has caused substantial damage to the Eastern states. Keep an eye out for white “fuzz” or wool on the underside of Hemlock needles. It is most obvious in fall, winter and early spring.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
Division of Entomology and Plant Pathology has a booth at the Indiana State Fair in the DNR Building and we also have a live butterfly exhibit. Last week, when I was there, I snapped this picture of monarchs enjoying butterfly weed in our exhibit. Stop by the state fair and see us and the butterflies!
I haven’t had much time lately for inspections, so the only thing I have to report this week is pear trees with an infestation of pear leaf blister mites.
The Indiana State Fair is in full swing and runs through Sunday, Aug. 18. If you’re attending, don’t forget to stop by the Invasive Species Booth in the DNR Building. We’ve got lots of information on all the latest invaders and there’s lots to see and do around the DNR Building including the Entomology & Plant Pathology sponsored Butterfly Garden!
