Indiana Department of Natural Resources sent this bulletin at 05/21/2019 07:34 AM EDT
Weekly Review for May 21, 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.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
I still have not seen many mite infestations in the field. Mostly, two spotted spider mite populations in greenhouse and garden center situations. I also have not seen any leafhopper activity on maples yet. During the past week, I found some aphids on Vanhoutte Spirea, but overall it has been a light year for aphids. Generally, aphids do not cause a problem and populations will decrease in numbers as new growth become less succulent over time. I continue to see numerous disease issues in garden centers. Botrytis is still a problem on many annuals. However, the warmer, drier weather will help ease issue associated with botrytis. I found a serious infection of apple scab on Pink Lady apple. It was very early to find such a large level of apple scab infection. However, the plants originated from an out of state nursery and were packed tightly together in the garden center.
The reduced air circulation from crowding likely exacerbated the apple scab infection level. Give your plants plenty of air circulation. I also found symptoms of shot hole fungus on Yoshino Cherry. Apparently, both bacterial and fungal infections can result in the shot hole appearance. Last year, I had about 75% defoliation on the Yoshino Cherry in my back yard and I also observed defoliation on Yoshino cherries at nurseries with shot hole leaf symptoms. This year my tree is growing fine with no current symptoms. I will keep you posted when symptoms begin to develop again. I also observed what appeared to be early stages of Septoria leaf spot on yellow twig dogwood. Yellow twig and red twig dogwood often get large amounts of Septoria leaf spot. It never seems to kill the plants, but they can look pretty bad in late summer which can affect there marketability.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
Last week, I continued with dealer inspections in my territory. One of the most interesting things I saw was suspected bacterial blight on rose of Sharon. This is very similar to a picture Angela took in her territory at a different store a couple weeks before, and mine was from a different supplier. I sent it to the Purdue Plant and Pest Diagnostic Lab for confirmation but I believe that bacterial blight will be the diagnosis. Later, I visited a different store when I was off duty and took a “quick look” in their garden center (couldn’t resist!) and saw the same issue on Rose of Sharon there.
I also continue to accidentally stick my hands into populations of aphids on an almost daily basis, such as these spirea aphids which I saw all over the spirea plants at each of a chain of dealers I visited on the same day. Lastly, I found some Persian lilacs with severe leaf spots in an unusual pattern, which is likely spray damage but I also sent to the lab for confirmation.
This week I’m sharing some photos of lab analysis confirmed Downy Mildew on Red Double Knockout Rose and ‘Baby Cakes’ Blackberry and also photos of bacterial blight on ‘Minerva’ and ‘Lavendar Chiffon’ Althea.
