Indiana Department of Natural Resources sent this bulletin at 05/27/2020 08:59 AM EDT
Weekly Review for May 27, 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.
Btk applications for Gypsy Moth were completed Tuesday morning in Huntington and Westville. Mating disruption treatments are scheduled for mid-June for sites in Huntington and Marshall counties. See our Gypsy Moth website for more information.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
The weather is finally warming up and I am starting to see a few more pests. Aphids were found on Spirea this week. I also found heavy infestations of aphids in a greenhouse. I really do not recommend spraying for aphids unless you are getting a high amount of leaf curl, honey dew or sooty mold. Most of the time predators and parasitic wasps suppress populations. Lady beetles are excellent predators, but parasitic wasps, which are often difficult to see, do a great job at controlling aphids. Look for brown, mummified aphids on the underside of leaves. During an inspection at a garden center I encountered active red-headed flea beetles feeding on Little Lime Hydrangea. The plants were shipped from Texas. This seemed a bit early to see activity from this pest, but the larva feed in the soil, and this pest can easily be shipped on nursery stock. Look for damage on Itea, Hydrangea paniculata, red twig dogwood and beautyberry. I typically do not see damage in my region until late June. I am continuing to see two spotted spider mite infestation in greenhouse environments. However, I have not seen any maple mites, spruce spider mites or southern red mite infestation so far this year.
The abundant rainfall and cool conditions has allowed the development of many plant diseases. I am finally starting to see the development of cedar apple rust on apples. Look for small orange spots on the leaves of susceptible varieties of apples. I have not seen any anthracnose on dogwoods, but I am starting to see some symptoms of Septoria leaf spot starting on red twig dogwoods. This leaf spot is very common on red twig dogwoods and often very difficult to control unless you have a diligent fungicide programs. During a greenhouse inspection I found cankers on the base of basil plants that were causing wilting and plant death. Interestingly, the same problem at the same greenhouse was found last year. It was only one variety that was being affected, but I was not sure which variety it was. I also found Zinnias wilting and declining.
Close examination revealed a white fungal mate growing on the surface of the media. This possibly could have been the fungus Fusarium causing damage to the Zinnias. The plants were of decent size but growing close together. Interestingly, I have not seen a lot of Botrytis this year despite having cool, wet weather. I am starting to see leaf spot develop on bearded iris. This could be Didymelina leaf spot. This fungus can also infect Belamcanda (Blackberry Lilly). However, I see this less frequently. Look for elliptical leaf spots forming on the leaves. Wet spring conditions often promote the leaf spot. High levels of infection can cause quite a bit of damage to foliage. The weather has really warmed up. I hope to have some more interesting finds this week that I can share with you next week. Also, I am sure something else in my yard will die due to the waterlogged heavy clay soils. I need it to rain 0.75 inches per week, every week instead of 5 inches in 3 hours and then nothing for 5 weeks!
It’s been a slow start to the season. The most common thing I’m finding is cold damage from the late freeze. Most of it is recovering and pushing out new leaves by now. Pest-wise, I’m seeing the usual suspects with the appearance of aphids on golden Alexander’s and cranberry bush viburnum. Spider mites have shown up in several locations on roses. I also found one particular rhododendron with an unknown defect that looked like viral damage but turned out not to be. At the moment it’s still up in the air as to the cause. One of the highlights while doing a new grower inspection was finding a cutleaf walnut, which was a first for me.
The weather has warmed up, and insects are on the move. If you get bee swarms in your yard or neighborhood, we have a list at that can connect you with individuals who can help remove the problem.
Rose slug sawfly is hitting the roses in my backyard pretty hard. Not a difficult pest to deal with and they shouldn’t harm the health of the plants, but the leaves can become quite unsightly and the damage will be there for the rest of the year.
I did get out for a nursery inspection where I found some of the heaviest thrips damage I’ve ever seen. While I found thrips on sedges and grasses, it was the Sweet Black-eyed Susan that was just demolished. Interestingly, the plants on the outside edges where I often see drought issues were the plants most effected. Other pests I encountered included aphids on sedge and powdery mildew on bleeding heart. Finally, I found a little bit of rust on buckeye, which was a new one for me.
