Indiana Department of Natural Resources sent this bulletin at 06/02/2021 10:05 AM EDT
Weekly Review for June 2, 2021
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.
I conducted some inspections in Noble County this past week. Aphids were probably the most common problem I saw. The new growth on roses, viburnum, spirea, and spruce all had aphids feeding on them to some degree. Roses and spirea by far had the worst infestations. I found crown rust on fernleaf buckthorn at one nursery. This disease is primarily found on oats, barley, rye and other grasses, but also uses buckthorn as an alternate host. Fireblight was present on Callery pear. The classic shepherd’s hook shaped dieback was affecting several trees. I found a heavy infestation of pine bark adelgid on weeping white pine. The trunks of the trees looked like they were covered in snow. There was also a quite a few lady beetle larvae feeding on them. The hatch of periodical cicadas is just beginning in Northeast Indiana. I saw my first one in Fort Wayne last Wednesday. I also got a report that they are quite active at Salamonie State Forest.
Perry County continues to have lots of reports of Brood X periodical cicadas, along with other reports of adults in tree canopies in many far southwest Indiana counties. I included a photo of a Brood X adult (notice the red eyes) and a photo of the ground emergence holes.
I have also included a photo of possible virus symptoms on Schipka cherry laurel. You can see in the photo that several leaves have chlorotic ringspot areas. Samples were sent to the Purdue Plant and Pest Diagnostic Lab (PPDL) and were tested for a couple of viruses that infect Prunus. Tests were negative. PPDL indicated that other diagnostic labs have seen similar symptoms on cherry laurel, have tested for additional viruses, and were not able to identify a virus. So the cause of this possible virus remains unknown at this time.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
One of the nurseries I inspect in Tippecanoe County called me out this week for a problem on Canaan firs. Many of the trees had bronzing on the needles and branches which was visible from a distance with the naked eye. When we looked closely with a hand lens we found the cause to be a bad mite infestation. I also saw my first tiny bagworms of the year today on white pine trees. At my house in Marion County it seemed like we had a break from the Brood X cicadas this past weekend with the colder temperatures, but on my drive home today I heard them out and singing. At least where I live, we still haven’t seen them in spectacular numbers.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
I am finally starting to hear some cicadas on the southwest side of Bloomington. However, there are still many areas that do not have cicada activity and I have not observed any in my yard to date. They are hit or miss in my region. Even bigger news is that bagworm has hatched in Greene County. This is by far one of the most destructive pests with a huge economic impact on the nursery industry. Treat them early and monitor for new sites that you missed or that blow into your nursery from storms. Look for small larvae starting to cause subtle browning on needle tips at this time of year.
There are some early season pests in which you may not observe damage until after the pest activity has subsided. During the last week I observed quite a bit of damage from spruce spider mite (Oligonuychus ununguis) especially on dwarf Alberta spruce in landscape environments. Look for browning needles, webbing and eggs at this time of year. Most of the adult activity has stopped for now as this is a cool season mite that feeds during the month of May. However, damage may not show up until tissue desiccates with warm weather. If there are an abundance of eggs observed, it may be a good time to apply an ovicide to prevent possible fall outbreaks that can occur. There is another type of cool season spider mite called the southern red mite (Oligonychus ilicis). This species prefers hollies and azaleas. I do not often see this in the landscape in my region but occasionally encounter it in the nursery industry. Look for plants to have older leaves that have a faded or grayish appearance. White shed skins and red eggs can often be found on the undersides of leaves. Damage from boxwood psyllid was found causing leaf cupping in certain areas. This is an early season pest that typically feeds in April. It is a bit late to treat for it now, but you may want to note areas where you find the infestation in case you want to treat next year. It does not kill the plant but alters the appearance.
I have also observed leaf galls caused by Eriophyid mites on both maple and fragrant sumac. These often appear as a small red bump on the leaves and do not cause serious injury to plants. Control is really not necessary unless you have a client that finds the damage objectional. I also saw leaf galls on hickory this week as well. I am not sure if this gall was caused by an aphid, psyllid or a mite. Remember a leaf gall is the plant’s reaction to the presence of a pest or pathogen. Galls can be caused by fungi, bacteria, mite or insect feeding. Finally, I have seen low amounts of leaf miner activity on daylilies. Interestingly I have not observed much thrips activity yet this year.
I did not observe many disease issues during the last week. Powdery mildew was observed on a susceptible host, but no noticeable cases of fire blight. My region has been very dry and has missed most of the rain. We only received 0.34 inches at my house last week. Anthracnose on sycamore and maples is quite common in my region as well. Sycamore anthracnose will delay leaf emergence. Anthracnose on maples will cause blackening leaves and sometime cause leaf drop if there is a large amount of infection.
It has been a slow spring for insect activity in East Central Indiana. This cooler weather has given spruce spider mite some good growing conditions. I’ve noticed some stippling at various locations. It’s important to remember that spruce and other evergreen trees and shrubs do not recover from the loss of chlorophyll due to mite feeding so control is important. Hot dry weather will decrease populations, but they are still there reproducing. There can be six generations or more per year.
Despite the relatively cool weather, Agapostemon virescens, the bicolored striped-sweat bee, has been busy building and expanding its nest.
In my neighborhood, maple petiole borer damage, maple bladder gall, and maple anthracnose are very noticeable. These issues have two things in common. First, by the time you see it, it is too late to treat. Second, they look serious, but really don’t have that great of impact on the overall health of the tree. Sycamore anthracnose is slightly more serious. This year the defoliation is heavier than I have ever seen, but the sycamores have already started leafing back out. With adequate moisture, in a couple weeks you will not be able to tell how hard they got hit.
In nursery inspections, I have seen the start of aphid populations on oaks, maples, and birch. Pine bark adelgid is out. I have seen a couple adult rose chafers. And I found oak pocket vein gall and aphids together on shingle oak.
