Indiana Department of Natural Resources sent this bulletin at 07/06/2022 09:12 AM EDT
Weekly Review for July 6, 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.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
Well, a little rain would be nice. It is so dry in my backyard that the weeds in the lawn are wilting. The good news is that I do not have a leaf spot problem on my Yoshino cherry or serviceberry this year. Lace bugs are having a feast on my serviceberry, but so far, I actually have leaves this year. During the past week I have continued to see serious two-spotted spider mite issues on many plants. The hot weather and lower-than-normal relative humidity levels have made very favorable conditions for this pest. While conducting an inspection I found a severe infestation of them on butterfly bush being grown in a greenhouse. I was lucky enough to find predatory mites, likely Phytoseiids feeding on two-spotted spider mites; however, their population levels were so high that it warranted a rescue treatment with a miticide even if it meant killing a few beneficial mites. Some miticides are less toxic to beneficial predatory mites than others.
Red headed flea beetles were found actively feeding on Hydrangea paniculata, red twig dogwood and Itea. Look for the Swiss cheese like holes in the leaves. I got lucky last week and was able to find a few adults hanging out on the undersides of leaves, but they are not always easy to find. Aphids were found feeding on swamp milkweed. They typically do not kill plants, but large numbers will result in leaf curl, reduced growth, and the proliferation of sooty mold. Look at the newest growth and the undersides of curled leaves. Damage from columbine leafminer was also found in the last week. I typically start seeing this pest in mid-May and new damage seems to taper off in summer.
I am still encountering some disease issues during inspection. It seems to be a great year for rust. Hollyhock rust was found in Vigo County. High levels of infection can result in leaf drop and make a plant unsellable. You cannot miss it. Look for yellow haloes on the leaf surface and orange sporulation. Powdery mildew was found on columbines. I also found symptoms of Phyllosticta leaf spot on pawpaw. However, symptoms were not dramatic this year. During previous years, these spots would enlarge and coalesce to form a large amount of necrotic tissue on the leaf surface. I also observed an unusual brown discoloration on the top side of knockout rose leaves. The grower thought it may have been caused by an application of neem-based products. I have worked with various neem-based products such as oils and azadirachtin and the viscosity of these products varies greatly. Plant sensitivity varies based on the exact formulation of these products. They are a good tool, but I have personally caused injury to roses when environmental conditions were not favorable for the formulation I was using.
This past week I didn’t really get any inspections done because I was on vacation for a few days in southern Illinois and then at the Heartland Apicultural Society (HAS) Conference in Evansville. However, I did find some interesting things while I was out. The first was a series of pits under the deck at the cabin we stayed at. The pits are traps created by antlions which excavate them with steep banks and bury themselves at the bottom to wait for an unsuspecting insect to fall in, at which point they can grab the insect and devour it. If the insect isn’t caught right away, they will use their head as a shovel and try and throw dirt/sand at the prey while it tries to scramble up the wall of the pit trying to make the trapped insect fall back down. I was telling my 10-year-old about them which resulted in a less than enthusiastic response. At that point I tried explaining to him that the ant lions were like the sarlacc waiting at the bottom of the Great Pit of Carkoon in Star Wars. He proceeded to vault the porch railing and spent a good while playing Jabba the Hut throwing insect victims to the lions.
The only thing that I found which was close to a nursery problem was in the University of Southern Indiana’s landscaping while I was at the bee conference. I noticed what looked at first glance like more coneflower rosette mite in some of the landscaping, but in this case the heads had turned green or partially green. This is not caused by a mite issue but is the result of aster yellows. Aster yellows is caused by a phytoplasma (bacteria) which is transmitted by leafhoppers. Once infected the only solution is removal of infected plants.
Finally, the majority of last week was spent at the HAS conference. If you are a beekeeper, conferences, bee schools, and workshops are well worth attending. I think I always hear a beekeeper at those meetings make a statement along the lines of, “I’ve been a beekeeper for 30 [40, 50] years and I just learned X”. At HAS I listened to Randy Oliver (from Scientific Beekeeping fame) give a number of interesting talks. I also got to talk one-on-one with Oliver, Kamon Renyolds, Blake Shook, Kent Williams and a number of full-time beekeepers from here in Indiana. I would encourage anyone who keeps bees or is thinking of keeping bees to attend events like these.
A couple weeks ago I attended a queen grafting workshop put on by my club (The Beekeepers of Southeast Indiana). This past weekend I used Randy Oliver’s guidance on queen breeding for hobbyists to try my hand at grafting a few cells from my most productive queen. I am happy to report that after putting together my cell builder I was able to get three of my four grafts to take. During the process of shaking the nurse bees off my frames I noticed I still had a lot of nectar coming in. After I was done grafting, I walked around to try and figure out what was the major source of the nectar still coming in. My button bush are a little past peak bloom but still were being worked heavily. I suspect the two main sources were my hairy mountain mint which just started blooming and a very large patch of dogbane which is on my property. I also noticed I had a few bees working some of my elderberry for pollen.
This week I have been seeing Japanese beetle adults out feeding on grape leaves and on ornamental plants. Also, I have been seeing a fair amount of rust on hawthorn. Here is a good reference for common rusts seen in the landscape.
Saw my first Japanese beetle of the season this week. They seem late and low in numbers so far this year. The spring drought may have done a number on them, but we will have to wait and see. Speaking of drought, even with that spot of rain we got, it was not enough to pull back on irrigation, so continue to keep an eye out on water status, especially on newly planted material and containerized stock. One more drought related comment – be aware of spider mites. Rain does a lot to knock them off the leaves and moderate the population. Between the heat and the lack of precipitation, I’ve seen some places where the populations are starting to cause some real damage.
