Indiana Department of Natural Resources sent this bulletin at 05/19/2020 09:05 AM EDT
Weekly Review for May 19, 2020
This informal report by the Division of Entomology and Plant Pathology is designed to update the Nursery and Greenhouse industry of insect and disease pests the Division has been encountering on a week to week basis and as a way to give a “heads up” of things to be on the lookout for. Comments and questions about this report are welcome and can be sent to your respective Inspector.
My old friend columbine leafminer is back. Of course, so is the volunteer columbine it has been feeding on for the last decade or so. I looked for the larva in the leaf, but I didn’t find them. Seems a bit early for the first generation to have pupated already given our cold temperatures, but this is a weird year. This leafminer can have three generations per year, but despite that kind of feeding damage, these plants come back year after year.
I didn’t get a chance to do many inspections last week. The main thing I was seeing was frost damage. At my house, I got to see cedar-apple rust in all of its glory. I have a rather large cedar tree and crabapple tree close to each other, so each year I get to see the cedar-apple rust galls on the Cedar put out their bright orange tendril-looking telial horns.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
I am finally starting to see a few pests become active in nurseries and landscape environments. However, most of the insect problems I am seeing are on greenhouse-grown plant material. During the past week I observed aphids on field-grown apple trees in Monroe County. There was leaf curl occurring at the tips, and when I opened up the leaves there was a small colony of black aphids. Wow, I finally found something that was not a plant disease. I have not seen any aphids on Spirea or any woolly birch aphids so far this year.
Two-spotted spider mite was found on Jasmine growing under greenhouse conditions. Look for stippling, leaf yellowing and webbing. Early stages of mite infestation often require a hand lens for detection. Adult two spotted spider mites are cream-colored, with two distinct black spots. Look for small colonies of mites on the undersides of leaves near the mid rib. Mite eggs are perfectly round with a pale yellow color or sometimes red depending on the species of mite. When mite eggs hatch, they look like the eggs, with just a few small legs protruding from the eggs. Dead mites will appear as white shed skins, and nonviable eggs will have a shrunken appearance and lack the perfectly round shape.
Cedar apple rust was found on Eastern red cedar this week. However, I have not seen any infection on apples so far this year. I also have not seen any apple scab on crabapples. In Vigo County, I observed a leaf spot infection on garden phlox. There are several leaf spot diseases that can infect phlox. Two of them listed in the literature include Cercospora and Septoria. Laboratory diagnosis is necessary to determine the exact causal agent. The plants in this case were being grown tightly together with little air circulation. Remember to maintain good air circulation around plants. When things are busy early in spring, plants are often potted and stored close together. It is easy to forget to spread those plants out when they grow larger. I have not seen any fire blight or Psuedomonas blight on susceptible host so far this year. I was thinking we may see some of these problems occurring with the recent freeze damage and wet conditions. It looks like a wet week, with warmer temperatures. Perhaps we will see a few more problems develop.
Things are definitely moving pretty slowly here in Central Indiana. I’m not seeing a lot of pest problems yet, but the second cold snap has done a number on a lot of different species. The tulip tree in my front yard was particularly hard hit by the last wave of cold. It was damaged earlier this year by a lightning strike, so it is under a lot of stress. The main thing I can do to keep it healthy is ensure it has a good supply of water when it needs it and prune out and dead material. Whether it survives long term, only time will tell.
