Indiana Department of Natural Resources sent this bulletin at 05/18/2022 08:10 AM EDT
Weekly Review for May 18, 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.
Sometimes it pays to stop and smell the flowers, or in this case the invasives. I noticed a patch of Japanese knotweed growing alongside the road in Hancock County. While I stopped to take a few photos, the farmer happened to be driving by and asked me about it. After a brief discussion, he assured me that he was going to release Armageddon on it! I will check back later to see what progress was made.
I managed to get to a number of my conifer growers this week. I found a small population of hemlock elongate scale as well as a fairly healthy population of pine needle scale. Left unchecked, scale can be a real problem. In the case of pine needle scale treatment timing has been off in the past and it has spread significantly. The hemlock elongate scale was rather difficult to find but has had more timely controls applied over the years. I also found a number of Canaan fir trees at multiple locations infested with balsam twig aphid. Fortunately, they do not cause much long-term damage and I have heard some people even like the look of the twisted needles on Christmas trees.
Lastly, I was asked to look at some hives. Upon inspection I found the hive already swarmed and had multiple queen cells which were ripe. As we were going through frames, I found one queen cell which had been partially opened and still had the virgin queen in the cell. We were able to observe late stage uncapped brood (probably day eight from egg laying) which tells us that the hive swarmed sometime less than eight days ago. I also moved three swarms (one prime swarm and two cast swarms) to a new location. The prime swarm was issued on May 1 and as of moving it on May 14 had approximately three frames of brood already laid up. The cast swarms issued on May 9 but both of those had eggs present when they were moved.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
Last week I did some inspections at box store dealers and the biggest issue I saw was drought stress. With the hot weather suddenly upon us, a lot of places just were not able to keep up on their watering. I also found a peony with suspected tobacco rattle virus and an aphid infestation on a whole rack of knockout roses that had just come in on a vendor truck.
The unpredictability of Indiana’s spring weather can be hard on our plants, especially those sitting in pots over concrete or asphalt while waiting for their new homes. Remember a good watering regime is critical to keeping plants healthy. While out doing inspections, drought stress was the number one issue I saw. The second was probable tobacco rattle virus (TRV). Symptoms vary depending on species, but TRV infects many herbaceous species. TRV can spread mechanically when tools used for pruning or dividing become infected, by nematodes carrying the virus feeding on plant roots, or it can be found in seeds from infected plants. The only control for TRV is to remove infected plants and dispose of them. To limit the mechanical spread of this and other pathogens remember to sanitize tools between cuts (or at least between plants).
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
I am starting to see an increase in pest activity in my region. During the past week I observed aphids on Spirea and Penstemon in the landscape. I have not yet observed thrips activity, but I did see thrips feeding on daylilies. No bagworm hatch yet and no leafhopper activity, but I think it will be very soon that we see these pests. However, the long-range forecast is predicting quite a cool down towards this weekend and this may delay some things. Two spotted spider mites were found on knockout roses at a garden center. It is a bit early to find this pest in the landscape. This infestation was likely sent to the garden center at a low level and the warm temperatures last week allowed the pest population to rapidly increase. Look for stippling and yellowing on the topsides of leaves and mite colonies on the undersides of leaves.
There can be multiple generations of this pest each year, so early intervention is essential to prevent serious plant injury. Columbine leafminer was found this week. This pest occurs early in the growing season and seems to be difficult to control. It never seems to kill plants but makes the appearance undesirable for sale. One interesting find I had this week was pear blister mite on an edible cultivar. I do not often see this pest. This is an Eriophyid mite that begins to feed on leaves during leaf expansion. Look for slightly raised blisters on leaves. Large infestation levels can cause significant leaf injury.
During the past week I have found a few disease issues. I am beginning to see leaf spot on susceptible varieties of Iris. One leaf spot that is known to occur on iris is Didymellina leaf spot, but lab diagnosis is necessary to truly determine which species of fungi is actually causing the symptoms. I also observed symptoms of tobacco rattle virus on ‘Sarah Bernhardt’ peony. Look for yellow mottling on the leaf surface of infected peonies. A laboratory test is needed to determine the exact virus which is causing the symptom, but I have had tobacco rattle virus confirmed on this cultivar multiple times.
Kallie and I have started a trace forward on a couple of loads of hemlock brought into Indiana from out of state with confirmed hemlock wooly adelgid. It is important to get a handle on this insect because of its devastating effects on hemlock stands and the ease it spreads by hitchhiking from one tree to another in bird feathers. This situation also demonstrates the importance of checking over all nursery stock shipments for pests and diseases upon arrival. To add insult to injury, some of these hemlocks also had moderate infestations of hemlock elongate scale.
