Indiana Department of Natural Resources sent this bulletin at 06/08/2022 08:05 AM EDT
Weekly Review for June 8, 2022
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.
A couple of weeks ago one of my nurseries had a received a lot of canna Richard Wallace with streaking on the foliage. Samples were sent to PPDL and the plants tested positive for a potyvirus, but further testing was needed to determine the exact one. The results of the testing have come in and revealed they were infected with canna yellow streak virus. Potyviruses can be spread by aphids, however I think the more likely cause in this case was through division of infected rhizomes at the nursery of origin since the entire lot was affected.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
Not many new pest problems this week. I am continuing to see an abundance of damage from the red headed flea beetle. However, I am also seeing other species of flea beetles beginning to feed on eggplants, which they are highly susceptible to. Flea beetles become active on eggplants around Memorial Day weekend in southern Indiana. Look for small holes in the leaves. Severe infestations can lead to skeletonization, shot hole damage and leaf drop. This is why eggplants can be quite a challenge to grow.
I frequently conduct log inspections for overseas export as part of my regular duty. Last week I found ambrosia beetle frass tubes being produced on oak logs. You may observe this on live trees as well. There are several species of ambrosia beetles that can make these frass tubes. Ambrosia beetles have the potential to be a serious pest on many trees and will feed on almost anything deciduous. I also found signs of Armillaria root rot (shoestring root rot). This pathogen is more likely to be found on older trees. In autumn this fungus will produce the honey brown mushroom at the base of infected trees. If the bark is removed from dead or declining trees you may see a white growth or an abundance of black, string like structures. These are called rhizomorphs and are actually the mycelium of the fungus.
Powdery mildew continues to be a problem on many hosts. During the last week I found multiple locations where bloom truck hydrangea was heavily infected with it. The plants were growing under shade cloth with reduced air circulation. Several years ago, there was a hydrangea series called city line. I frequently found powdery mildew infections on these plants as well. Rust was found infecting mallow plants at many locations. Look for leaf yellowing with orange fruiting bodies on the undersides of leaves. The cases I found this week were causing significant leaf drop on plants that were heavily infected. I am still waiting to find my first fire blight infection.
Now onto the cultural problems I am seeing. Many garden centers do not put enough water on pot bound plants. Drought injury and stress was found at many garden centers during the last week. Although the weather has not been excessively hot, we have had some very dry conditions with low relative humidity levels. This weekend, the relative humidity at my house was 22%. This makes it feel great in the shade, but pots will dry out quickly with these conditions. During inspections I also found trees that were still tied up after shipping. Things get a little crazy in spring but remember to untie plants as this become especially important during hot weather conditions.
Much of what I write about seems to be gloom and doom. However, I do love plants. Recently at a garden center I found cones on a Japanese umbrella pine (Sciadopitys vertcillata). I do not often see cones on this plant so it was a chance to share something interesting to you other than plants that have pest and disease issues.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
Last week, the division received tons of calls about poison hemlock. Driving around in my district, it’s easy to see why – poison hemlock is flowering now and this is probably when most people are likely to notice it. It seems to be everywhere along farm fields, railroad tracks, and any unmowed transportation rights of way. I’ve also noticed it in yards in my Marion County neighborhood. I am including some pictures I took last week of poison hemlock flowers, stems, and leaves. For a really in-depth write up on identification and management of this plant, I’m always a fan of OSU entomologist Joe Boggs’ blog entries for BYGL.
Photo 9-12 - Poison hemlock identification photos
At inspections last week I found a bad case of boxwood leaf miner on some green velvet boxwoods, four-lined plant bug damage on perennial geraniums, possible virus on delphinium (awaiting lab confirmation), and hollyhocks with both sawfly feeding damage and rust.
I have not had many new finds while inspecting nursery stock in the last couple weeks. I’ve seen more scale, including more lecanium, Japanese maple, and fletcher. I have noticed a bit of an uptick in the amount of powdery mildew which isn’t all that surprising considering the cooler/wetter weather we have had.
I will go ahead and throw out another reminder to any plant retailers that wintercreeper and barberry are both on the Terrestrial Invasive Plant Rule. I am still getting reports of the occasional plant being sold. If anyone would like to report a species being sold in violation of the terrestrial plant rule you can find the inspector covering your area at the following link.
I had a couple bee calls last week. The first was from an individual that thought they had American Foul Brood which was a false alarm. The second call was for European foul brood which was not a false alarm. We examined several hives in a 30+ hive apiary which had the distinctive sour smell and exhibited infected larvae. EFB is a bacterial disease which infects the gut after being fed bee bread containing bacteria and kills the larvae and possibly pupa. Besides the odor symptoms typically include spotty brood pattern, contorted larvae (not a C shape in the bottom of the cell), larvae with a yellow tint, off color royal jelly and slumped puddles of goo or scale in the bottom of the cell which are the decomposing remnants of infected larvae. If the colony is weak the nurse bees cannot keep up with removing the dead larvae / pupa. In this case a brood break by requeening or other means can help the colony catch up on housekeeping. Requeening may also be able to introduce more hygienic genetics in a new queen which will help with the infection. You can also treat with Oxytetracycline or Tylosin but you will need a prescription (Rx) or a veterinary feed directive (VFD) from a livestock veterinarian in order to obtain the antibiotics and they must be used in accordance with the vet’s direction.
I have included a couple of photos this week. The first is powdery mildew on moonswirl tickseed (Coreopsis grandiflora). The other photo is of concrete mites, also known as pavement mites or sidewalk mites. These mites belong to the genus Balaustium in the family Erythraeidae.They get their name because they tend to aggregate in sunny areas on patios, sidewalks, walls, and concrete areas. These mites are bright red and fast moving. They are predaceous and eat other mites and small insects. They also supplement their meat diet with pollen, as shown in the photo.
Being the editor, I have the advantage of reading everyone else’s articles before writing my own! For the sake of brevity, I too have found powdery mildew, Japanese maple scale, wilting plants from a lack of watering, and far too many barberry and wintercreeper from the Terrestrial Plant Rule.
