Indiana Department of Natural Resources sent this bulletin at 08/30/2023 07:21 AM EDT
Weekly Review for August 30, 2023
This informal report by the Division of Entomology & Plant Pathology is a commentary on insects, diseases, and curiosities division staff encounter on a week-to-week basis. Comments and questions about this report are welcome and can be sent to your respective Inspector.
This is the last regular issue of the Weekly Review for the 2023 season! Thank you to everyone for your interest in what we do and for your questions and comments. We will use this email list to send out news and updates sporadically through the winter and be back with you weekly around April 2024.
Vince Burkle (Assistant Division Director & Nursery Inspector) - VBurkle@dnr.IN.gov
I've noted a few walnut petiole galls in the last couple of weeks and even had a homeowner contact me concerned it was the reason she was losing branches. While this particular gall may cause some leaf deformation, it doesn’t harm the vascular flow and isn’t the cause for other damage on the tree. The galls are caused by an eriophyid mite. In large numbers, it could cause a lot of deformation, but there’s no evidence that deformation causes significant harm to the tree.
I also was able to catch a nice population of two-spotted tree hopper (Enchenopa binotata), also called two-marked tree hopper. While feeding does cause honeydew (and can lead to sooty mold), these sap feeders don’t usually warrant treatment since damage is very minimal.
What I have been seeing in the last couple of weeks that causes a lot of damage is verticillium wilt. I’ve only seen it in maples so far, but it’s been a few years since I’ve seen much of it at all. Purdue Extension has a great handout with information about susceptible and resistant woody plants.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
At an inspection this week I came across a few rows of serviceberry bushes where many of the plants had fireblight. They had the classic “shepherd’s crooks” on the tips of some branches, the tips had darkened and died back, and leaves had fallen off. Fireblight is a bacterial disease that can be spread through contaminated pruners, wind, rain, and insects. Diseased branches can be pruned out during the dormant season. Some sources I read said to prune 4 inches below the diseased tissue and some said up to 10 inches. Pruning tools should be disinfested between cuts to prevent further spreading the bacterium.
While on a recent inspection, I found a very interesting yet beautiful growth on branch tip of a white oak. After some time, our group of inspectors settled on the likely identification being oak rosette gall. This gall is caused by the tiny wasp, Andricus quercusfrondosus. The gall-making culprit is a wasp larva that induces the plant to grow a dense cluster of small leaves for protection as it stays in the leafy gall throughout winter and exits in spring.
