Indiana Department of Natural Resources sent this bulletin at 07/21/2021 07:30 AM EDT
Weekly Review for July 21, 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.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
I do not have many new pests to report over the last few weeks. So far, I have had 16.53 inches of rain at my house since June 3. This has been one of the wettest summers I have ever seen. Some of the plants in my yard that are not performing well include butterfly weed, cosmos, and Penstemon. They are not too happy with all of the rain and are getting crown rot and dieback.
Bagworms are still active and I have seen some damage on white pine in Brown County. However, I have seen very little bagworm activity in nurseries this year. So far this year, I have observed three Japanese beetle adults during inspection. Yes, that is correct, three adults. They are just not around. This is interesting because bagworm and Japanese beetles are usually some of my most abundant and damaging pests that I find during inspections, but they are at very low population levels this year.
I am continuing to see red headed flea beetle damage and some adult activity in nurseries and landscape environments. This damage looks a bit different than Japanese beetle feeding injury. It typically occurs more towards the center of the leaf and makes a swiss cheese like appearance on the leaves. Older damage may cause browning of tissues along the margins of the feeding areas. I am seeing this in both the landscape and nursery industry. I have infestation in my backyard on plants that have been in the ground for 15 years. This pest is becoming established in Indiana.
Fall webworm was found on swamp white oak. Look for tents located at the ends of branches. Customers often have concerns about this pest which really is causing minor damage. Another pest that looks serious but does not usually cause significant plant injury is the flatid planthopper. Look for wax material on the stems of infested plants. Sometimes you can find an adult that is white and hops away when disturbed. I also have observed cypress twig gall midge on bald cypress. This pest causes white galls to develop on the stems of bald cypress. It may look unsightly, but typically does not cause serious issues to the overall health of bald cypress.
Recently, I found pockets of oystershell scale causing damage on American beech. This scale species has numerous hosts and often will heavily infest a single plant in the nursery. This is a difficult scale species to control, and it will cause serious injury to plants. It is extremely small and can often go unnoticed until plant injury begins to develop. Heavy populations will cause stunting, leaf yellowing and branch dieback. I found a single magnolia scale on saucer magnolia. This pest can become abundant and cause branch dieback, sooty mold, and branch dieback on magnolias. Its life cycle is similar to the tulip tree scale. I more often find tulip tree scale on magnolias than magnolia scales, so this was a fun find for me.
Zimmerman pine moth was found on white pine in Monroe County. Look for gummosis and frass occurring at branch junctions. This pest is more commonly found on hard pines, but I have found it on white pine and even one time on Douglas fir. Large level populations can weaken trees and result in stem breakage. Chemical control should occur in April as larvae become active after overwintering in bark.
There are numerous leafspot and crown gall disease issues that are occurring in the nursery industry and landscape. Most of these problems cannot be easily identified in the field. During the past week, I found Septoria leaf spot on red twig dogwood. I also fond symptoms of Cercospora leaf spot on black gum or tupelo. This disease often appears as a small, pinpoint leaf spot. However, I have encountered cases where Cercospora has caused large necrotic lesions on leaves. Remember, what you are seeing in the field is a plant’s reaction to an infection that results in a similar set of symptoms. The same disease may express a different set of symptoms on a different host. This is especially true for certain turf grass disease. When in doubt, sent it out (to the lab). Next week I hope to share with you some problems in my back yard.
This week has been a good week for Japanese beetles. Although, I am seeing more active adults this week than last, damage has not been as bad as the last several years, at least not yet. Tar spot on maples is starting to be noticeable from a distance. I haven’t seen it at any level that would be concerning yet though.
Black knot fungus (Apiosporina morbosa) is a fairly common disease of Prunus spp. It overwinters in the galls. Galls start out as swollen areas on branches or trunks with a velvety, green color covering of fungal growth. It’s during the second year of growth that galls turn black and hard. It is at this stage where spores are released. Wet springs will precipitate the releasing of lots of spores. Wind carries spores to other trees where they easily infect wounded tree issue as well as new, green, tender growth. In some cases, the galls completely incircle branches causing all tissue beyond this point to die.
Management strategies will depend greatly on what’s infected and how badly it’s infected. Some species have better defenses again black knot than others, but removal of the inoculum will greatly reduce further infection and help protect more vulnerable trees.
This rain is starting to hinder bees and beekeepers. When it rains the bees stay in their hives. They are not getting extra honey and are eating what they have stored. Bees are also susceptible to chalkbrood or European foulbrood if the hives are in a wet area and in shade. When it rains this much beekeepers could also have trouble getting into some of their apiaries. It is always a good idea to determine if a site is flood prone and move hives to higher ground. It’s also nice to drive to an apiary and not get stuck!
Inspections are going on between rainstorms. I was in northwest Indiana for an inspection. When I got there a beekeeper’s hive had swarmed that morning. I helped her get the swarm into a hive body. We took a hive box with foundation and one drawn comb and set it on a bottom board. The bees were about five feet off the ground, so they were easy to get. The only thing is it was on a branch that went through a fence. I held the hive up under the swarm and had the beekeeper start brushing the bees into the box. Then we started to cut some of the branches and shake bees into the box. We set the hive down on the ground with the hive entrance facing a bunch of bees that fell to the ground. When we saw the bees start marching into the hive, we knew we had the queen in the box! We put the inner cover and top cover partially on so bees can fly into the hive. I like to smoke the branch that the bees swarmed onto to get rid of any queen pheromone that may be there. Within an hour the bees were in the hive. Sorry no photos - I had to hold the hive!
Be aware of YouTube beekeeping! I watched a video where someone placed a sheet on the ground with a tub or carboard box in the middle. Then they shook all the bees on the sheet then collected them into the box. Why would you use a sheet? It looked like too much work. Besides, you could kill the queen doing that.
I am starting to notice plant material that looks “tired”. That is my general term for the accumulation of seasonal cold stress, heat stress, water stress, insect feeding, and foliar diseases that pile up as the season wears on. Japanese beetles seem to be hit or miss. On maples, mites were ramping over the last week or so and potato leafhoppers seem light. I have seen a bit of fall webworm just getting started. I’m really concerned about the amount of red-headed flea beetle damage I am seeing. While the adults seem to be easily controlled, I have to wonder if eggs have already been laid to contribute to next year’s brood.
In contrast to my last curious find, this week’s is actually well-studied. The white-margined burrower bug, Sehirus cinctus, is native, has an extremely wide host range, and often feeds on lawn weeds such as henbit and purple dead-nettle. While it is occasionally found in larger numbers, it does little horticultural damage. Of interest, the adult female burrower bugs take care of their young!
