Indiana Department of Natural Resources sent this bulletin at 07/15/2021 07:22 AM EDT
Weekly Review for July 15, 2021
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.
The 2021 Indiana Cooperative Invasive Species Management Areas (CISMA) Conference will be held August 4-7, 2021. This year’s event, titled “Why Do We Manage Invasive Species?” will be multi-format with virtual sessions on Wednesday and Thursday followed by in-person regional field events throughout Indiana on Friday and Saturday. Registration is $25. Please visit the conference website for schedules, registration, and more information.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
Last week I found several yellow twig dogwoods with dark brown cankers on the lower portions of the stems. The stems were also wilting, and there was some defoliation. I sent one of the plants to Purdue’s Plant & Pest Diagnostic Lab where they diagnosed the fungal issue as Botryosphaeria canker and dieback. The pathologist at the lab recommended pruning out any discolored wood below the cankers but warned that if it’s not caught early enough, the canker can enter the main trunk, and the tree will eventually die. Another issue noted by the pathologist was severe root rot, which was not surprising, as the nursery has a standing-water issue in some of their hoop houses. We noticed several other species of plants with suspected root issues during the inspection as well. Root rot can stress the plant, which can exacerbate other pest and disease problems.
One other interesting find was 'Jethro Tull' Coreopsis with two unusual leaf symptoms – yellowing spreading out along the leaf veins, and dark brown or black leaf spots. The yellowing is likely caused by phytotoxicity (damage caused by pesticides or other chemical applications), and it tested negative for viruses previously found on Coreopsis. The dark leaf spots were bacterial, either Pseudomonas or Xanthomonas (awaiting final confirmation on genus from PPDL).
This week I have included a photo of oak shothole leafminer (Japanagromyza viridula) damage. This leafminer is a very small fly that utilizes oak leaf buds in the spring. The damage is caused by the ovipositor piercing the buds. As the bud breaks and the leaves expand, the holes enlarge. The damage to the leaves will often have this symmetrical pattern.
Beekeepers are taking off honey right now. The nectar flow will slow down as the spring flowers finish. With the rain we have been getting, the Dutch clover is still blooming. If we continue to get rain, the clover will continue to bloom.
With the nectar flow not as strong, it will be harder to get bees to draw comb. If you have frames that still need to be drawn out, move them between two frames of brood. Also, keep feeding them 1:1 sugar mixture. Once the hive has two deep brood chambers with fully drawn frames, then you can stop feeding.
Keep an eye on queens. If your hive swarmed, watch the new queen. She may not have been able to get out enough due to all the rainy days this spring. If she is not doing her job, replace her as soon as possible with a purchased mated queen or queen cell. Don’t let the hive make a new queen as she may have the same inferior traits as her mother. Instead, purchase a mated queen or queen cell.
This is also the time to do a varroa mite check on your hives. If you get more than 3 mites per 100 bees, you should treat. Depending on your treatment, you may need to remove honey supers. When you treat, treat all hives in that apiary at the same time. Many people think bees stay in their own hive. When you have hives in rows or close to each other, the bees may drift to another nearby hive. The guard bees will let the workers in if they have food. The guard bees are saying “Sure, come on in and we will take that honey.” This intermingling of bees can allow varroa mites to spread between hives and underscores the importance of treating every hive in the apiary to control varroa mites.
There have been several studies on how bees identify their hive. Putting a different marking on the front may help the bees identify their hive. If you have the room, putting hives in a circle facing out can help also. You just need to have enough room to do that. Many commercial beekeepers have four hives on a pallet, each one facing a different direction or two hives facing the same direction. I prefer two facing the same direction, so you don’t have to stand in front of a hive entrance when inspecting. If you block the entrance for too long the bees will go after your ankles.
