Indiana Department of Natural Resources sent this bulletin at 05/06/2020 09:58 AM EDT
Weekly Review for May 6, 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.
Things have been a bit slow up here in the northwest part of the state but I did get to do a couple of greenhouse inspections. Overall, things were pretty clean. I found some Botrytis on the typical suspects such as Begonia, New Guinea Impatients, Geranium but none of it was very bad. I found Alternia Leaf Spot on just a couple of New Guinea Impatients. Thrips were on Gerber Daisy, Verbena, Scaevola, Calla Lilies and Peppers. I only saw spider mites on Spikes. And the only aphids I found was a population that was doing quite well on Cyperus papyrus.
Wilting foliage was noticed on red buckeye in Allen County. After closer inspection buckeye petiole borer Zeiraphera claypolean was found.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
The pest season is slowly starting in my region. I finally saw one small infestation of tent caterpillar in northern Lawrence County this past week. I also observed some aphids on greenhouse grown mums but I have not seen any aphids in the landscape. Parts of my region received heavy rainfall during the weekend. I found botrytis on Dragon Wing begonia, but I am not seeing a great deal of botrytis this year. However, the cool wet weather this week may change that. I found symptoms of downy mildew on Arapaho blackberry plants. Samples are being sent to the lab for confirmation. The damage appears as multiple purple lesions on leaves that sometimes develop a tan center.
Last year when I saw this I thought it was some type of anthracnose or phytotoxicity, but based on my experience from last year I believe it to be downy mildew again. I have not seen downy mildew on knockout roses this year. However, I am seeing a lot of black spot already on roses that are being shipped from Texas. I also found symptoms of needle cast on Canaan fir and white pine at a nursery in Lawrence County. Samples are being sent in for lab confirmation. In the past, Rhizosphaera needle cast was confirmed on Canaan fir at this location. Look for browning of inner needles with small black fruiting bodies on the undersides of the needles. Firs can also get browning of needles from previous spruce spider mite feeding injury and abiotic factors. I am also seeing some nutrient deficiencies on greenhouse grown annuals brought outdoors.
I observed plants that had interveinal chlorosis, which indicates a micronutrient deficiency, usually iron. Next week I will show you so more plants that are not doing so well in my backyard. Some of the problems I have not figured out yet. Looks like my dwarf conifer collection is getting smaller this year. No pun intended.
