Entomology & Plant Pathology Weekly Review, June 27
Indiana Department of Natural Resources sent this bulletin at 06/27/2024 10:22 AM EDT
Weekly Review for June 27, 2024
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.
Will Drews (Nursery Inspector & Compliance Officer) - WDrews@dnr.IN.gov
I’ve been noticing a lot of issues with roses (Rosa spp.) in my area. Besides spider mites (which most of my colleagues have mentioned as being bad this year, and I’ve noticed them being pretty pervasive here, too), I’ve also spotted a lot of rose sawfly damage and some viral issues. There are three different species of rose sawflies that impact roses and can cause some significant damage to the plants. The two species I’ve noticed in the area are roseslug sawfly (Endelomyia aethiops) and bristly roseslug sawfly (Cladius pectinicornis).
All rose sawflies eat either partially through the leaves (“windowpaning”) or eat entirely through the leaves, creating small holes. Large populations can cause significant damage to an individual plant. However, not all rose sawflies have the same pest lifecycle. The roseslug sawfly only has one generation per year, so its damage is mostly cosmetic and should not adversely affect the health of the plant. On the other hand, the bristly roseslug sawfly can have multiple generations per year, if the weather conditions are right. So, their damage can accumulate throughout the year, becoming more noticeable and potentially adversely affecting the health of the plant. Rose sawflies can be treated using manual or chemical control options, if desired.
The other major issue I’ve spotted in roses is viral, most likely a rose mosaic virus. There are several specific viruses that cause rose mosaic virus. Some of the symptoms of these viruses include ringspots, yellow line patterning, and mottling. These symptoms can appear only on a portion of a plant and can be irregular. Unfortunately, once a plant is infected, there is no cure. Affected plants should be removed and destroyed. One positive note is that the viruses are not transmitted easily (like through pruning or via an insect vector). The main transmission pathway appears to be through the vegetative propagation of roses, either using infected buds, scions, or rootstock in budding and grafting.
There is a lot of debate about what bees work, with some beekeepers having a wide range of suggestions to plant and others to avoid. At a recent bee meeting where I gave a presentation on nutrition, the conversation focused on what to plant, and it was the typical “ask 10 beekeepers one question and you will get 11 responses.” And, as is in most beekeeping related things, the answer is complicated, but we do know that bees will work a wide variety of floral sources but may ignore some that they might normally work if something more attractive is in bloom. It may be that there is a more attractive flower, but it could also be that there may be similar cultivars that are more or less attractive. When cultivars are released, the sole selection characteristic is aesthetics. But we really have no idea what that aesthetic selection has done to nutritional content or production. Below are a couple of variations I have observed while doing inspections lately.
Photos 7–9 – Veronica Snow candles (white), Veronica blue (purple), and Veronica Pink candles. With three of these varieties lined up, Snow candles and the blue were getting quite a bit of activity, while the pink had very little. Interestingly all three had lots of bumblebee activity, and I couldn’t really discern any difference in their activity.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
In the last week or so I’ve noticed sudden and substantial feeding damage on sunflower plants in my home garden. I never found anything feeding on them during the day, so I went out after dark and found hundreds of what I believe to be Asiatic garden beetles chowing down. This is the first year I’ve found this beetle here. I’ve found them feeding on celosia, zinnia, bachelor button, bee balm, English daisy, Thai basil, cosmo, toothache plant, and several other species, but the largest concentration of beetles and heaviest damage by far has been on my row of sunflowers. Coincidentally, I happened to read an article about this pest the day before I found them for the first time in my own garden. Check out this article about Purdue researchers fighting Asiatic garden beetles on Indiana mint farms.
