Indiana Department of Natural Resources sent this bulletin at 05/25/2022 09:51 AM EDT
Weekly Review for May 25, 2022
This informal report by the Division of Entomology & Plant Pathology is a commentary on insects, diseases, and curiosities division staff encounter on a week-to-week basis. Comments and questions about this report are welcome and can be sent to your respective Inspector.
Eric Bitner (Nursery Inspector & Compliance Officer) - EBitner@dnr.IN.gov
Spotted lanternfly (SLF) nymphs have started hatching! We found first instar SLF nymphs that had just hatched from their egg masses in Switzerland County on May 10. The DNR plans to continue treatments to reduce the population and limit spread of SLF throughout the known infestation area. In addition, DNR has a trapping program set up for the 2022 season to determine the presence or absence of SLF in Indiana. Trapping will occur in Switzerland County as well as near major highways and railyards across the state where the risk of SLF hitchhikers is high.
Please assist the DNR in our effort to locate and control this pest by reporting any potential sightings to 1-866-NO EXOTIC. (1-866-663-9684)
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
We have had some hot weather during the last few weeks and quite a bit of rain in some parts of my region over the last week. I am continuing to see two-spotted spider mites on roses at some locations. Aphid problems are increasing on some plant material, but overall they have not been that bad yet. Pine spittlebug was observed on Scotch pine in Monroe County. Look for white, spit-like masses on infested trees. While this insect is usually more of a nuisance, large population levels can provide a secondary point for infection of pathogens.
Large infestations of this pest are rare. I found a leaf gall on the underside of a basswood leaves in Vermillion County. This is something I do not often encounter. Most leaf galls do not cause serious plant injury. The cause of leaf galls can be from insect feeding such as aphids, phylloxera and eriophyid mite species. The causal agent in this case was thought to be an Eriophyid mite called Eriophyes tiliae. There are also leaf galls, such as the azalea leaf gall, that occur from fungal infections.
Now on to what is not looking good in my backyard. The other day I was working in my garden and I noticed that the southwest side of my Ilex verticillata sparkleberry was not leafing out and had an abundance of dieback. At first, I thought the problem may have been associated with fluctuating winter temperatures and cold injury. However, this plant is a cultivar with native parentage and I thought that would be quite unusual. After looking closer I found oyster shell scale. It must have been a mid to late summer infestation that I did not see with the leaves on and the berries in the fall. They are definitely hard to see, especially with my old eyes. I do not often see this pest infest this plant. Keep an eye out for it - the color of the insect often blends with the bark and can make it difficult to detect. Close examination can reveal crawlers. Scales with small, circular holes in their covers have been parasitized. I missed it on this one and paid the price. I have included some pictures for your viewing pleasure.
I am beginning to encounter a few more disease issues as the weather becomes warmer. Symptoms of anthracnose were found on the red maple tree in my front yard. Look for dark irregular patches on the leaves. High levels of infection can cause leaves to have a tattered appearance and may result in some leaf drop. Sometimes anthracnose can look similar to tar spot, but tar spot is typically a late season disease while anthracnose usually occurs after a period of cool, wet weather. I am also starting to see low level infections of apple scab on susceptible varieties of crabapples and edible apples. This disease can be difficult to control unless multiple fungicide applications are conducted. It is best to plant resistant varieties whenever possible. Powdery mildew continues to be a problem on knock out roses at many locations. During the past week I observed powdery mildew infections that were severe enough to start stunting the new growth on infected plants. I have not observed downy mildew on knock out roses this year.
Scale was on the menu again this week. I was forwarded some photos by a homeowner who was worried about the presence of lichen on their maple trees. Fortunately, I was able to tell them the lichen was no concern, but I did notice that they had a heavy infestation of Japanese maple scale (JMS). I instructed them to wrap some electrical tape around the trees inside out so that they could monitor for crawler activity and was forwarded the following picture with numerous crawlers stuck on the tape. JMS can be extremely hard to control because it has an extended emergence period and can have overlapping generations which can require multiple control applications. Another issue with JMS (and other hard scales) is that they feed on plant cells which bypass the vascular tissue of the plants. Often times this is why the use of some systemics does not provide adequate control of these insects. In addition to my homeowner call, I was hanging a box-tree moth trap at a nursery in a hawthorn located in the landscaping adjacent to the boxwoods. Upon hanging the trap, I noticed another heavy infestation of JMS. This was not the first time I have seen nursery pests established in landscaping over the years. I have seen a correlation where established landscape pests are a problem in the production crops of a number of nurseries. The other scale I saw this week was fletcher scale in taxus. Fortunately, I have never seen fletcher scale get to the point where it is causing problems, even in heavy infestations.
At a large greenhouse I also ran into what appeared to be a good example of nutrient deficiency in butterfly bush. I couldn’t really explain why this was restricted to so few plants as this location uses one ton bulk potting mix and the number of plants effected wasn’t in my estimation enough to use an entire pallet of substrate.
In the southeast part of the state where I am at, the black locust blooms are starting to fade but the tulip poplar is going strong. My false indigo bush (Amorpha fruticosa) has just started blooming and button bush is not far behind. Some perennials like amsonia and baptisia are also blooming although they are minimal nectar producers, if at all. Hyssop, milkweed, and mountain mint, which are all major nectar producers, are still a little ways from blooming.
I conducted inspections in Allen County this past week. One greenhouse mentioned to me that they were having problems with canna Richard Wallace. They said the foliage was not supposed to have yellow stripes and the plants were stunted, and the problem was affecting the entire lot. I took a couple of plants and shipped them to PPDL and they came back positive for a potyvirus. The exact type of potyvirus is not currently known, however we are having additional tests run to determine which one it is. In addition to the cannas, I found light instances of Botrytis scattered throughout the greenhouse on begonia, geranium, and New Guinea impatiens. Two spotted spider mites were also found on dianthus and tropical hibiscus. While looking at trees around my property I found a couple of calico scale on a small pecan tree. I scraped them off and there were numerous eggs underneath them.
While doing nursery dealer inspections, the number one issue I’m seeing is plants not being properly watered. The second is tobacco rattle virus (TRV) on peonies. I have found it on a number of varieties at different locations. I know several other inspectors are seeing it as well. TRV is spread when nematodes feed on the roots of infected plants and then infect new plants as they continue to move and feed. It is also transmitted when tools used for pruning or dividing plants become contaminated, or via seed from infected plants. Good sanitation and disposal of infected material is important for control of the virus. It can infect many different species and symptoms vary depending on what species is infected.
I’ve started to see a bit of eastern tent caterpillar popping up here and there. Spider mites seem to be primarily coming in on imported tropical plants. I’m getting quite a few calls from nurseries and homeowners about the odd issue here and there, but no consistent problems yet.
We completed the Btk portion of the spongy moth treatments on May 23. Mating disruption treatments will start late June. Visit our webpage or follow us on Twitter for more information.
