Indiana Department of Natural Resources sent this bulletin at 05/30/2019 09:13 AM EDT
Weekly Review for May 30, 2019
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.
Despite the wet weather, we completed the Bt treatments for Gypsy Moth last week in Porter, LaPorte, and Fulton counties. The mating disruption treatments are planned for mid-June in Wabash and Fulton/Marshall Counties. As always, treatment timing is weather dependent. More information can be found at our Gypsy Moth Program page or follow us on Twitter.
This year has been full of surprises. Inspectors have been very busy investigating several pest introductions into the state this spring. In all cases, investigations are ongoing and it will be some time before we know if/how Indiana will be impacted. In the meantime, let me point you toward some good starting points to brush up on two of these diseases. If you have questions, please be sure to get in touch with your inspector.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
Last week on dealer inspections I was seeing a lot of evidence of ambrosia beetles on fruit trees at box stores. These trees were already dead or dying, and when I lifted up the paper covers on the trunks, “sawdust” would fall out. After a little searching I found the holes made by ambrosia beetles, although the paper trunk covers broke off the frass “toothpicks” you might normally see. I also found suspected rose mosaic virus on a few roses at one of my nursery dealers. At one greenhouse, all of the eggplants and many of the surrounding vegetable plants were covered in aphids. My most interesting find was a white-margined burrower bug. I wasn’t familiar with this bug but upon doing some reading I found that they are known for their unusual maternal behavior, in which the mother bug stays with the young for a few days and brings them food until they are able to survive on their own.
Kristy also helped me out with inspections last week and she found “Red Sunset” maple with heavy leaf spotting. We sent a sample to Purdue’s Plant and Pest Diagnostic Laboratory (PPDL) and it turned out to be maple anthracnose, probably Aureobasidium apocryptum. They said these diseases have been worse this year due to frequent rainfall but the trees should be fine, however, spacing out the trees and avoiding overhead irrigation will help prevent its spread. We also saw a lot of thrips scattered throughout one of the greenhouses we inspected, and Kristy was able to get some pretty cool magnified pictures using her hand-lens and phone camera, a skill I haven’t quite mastered yet.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
Last week, I attended a bark beetle workshop at Virginia Tech in Blacksburg, Virginia. This amazing group of insects can be as small as 1-2 mm, but they can be very damaging pests. I have not conducted many nursery inspection in the last week. However, I wanted to report what I am finding on my property. I finally found woolly birch aphids on river birch. Look for leaf cupping and woolly aphids located on the undersides of leaves. Their activity on my property was a bit late this year, but I am now seeing them. However, I did not see any aphids on my Spirea this season. Symptoms of spot anthracnose were found on my flowering dogwood. This fungal disease causes small, round spots on the leaves and it often occurs earlier in the season compared to Septoria leaf spot. I also found strong viral symptoms on the Oenothera on my property.
In the past, I have had tobacco rattle virus confirmed on this plant species at other locations. The plant is very aggressive and I have not seen any decline at this time, however this is the first year I have seen this symptom on my property. Tar spot has already developed on my red maple tree. This is a fungal disease that infects maple and hollies. Typically it is a late season disease associated with prolonged periods of high relative humidity levels. Look for black areas on leaves that feel slightly raised on the surface when you rub your fingers over them. This typically does not cause major issues for trees but can look bad for customers. Finally, I am seeing what appears to be iron chlorosis on my big leaf hydrangeas. I have not fertilized yet this year and they are growing next to a concrete was, so nutrient deficiencies resulting from high pH soils does not surprise me in this setting. I will keep you posted on the problems I am encountering. Something else is bound to die in my yard this year.
