Indiana Department of Natural Resources sent this bulletin at 05/10/2023 08:35 AM EDT
Weekly Review for May 10, 2023
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 have not conducted many inspections in the last week. I did have one interesting find on bonfire patio peach. During an inspection I found what I believe is white peach scale (Pseudaulacaspis pentagona). This scale insect looks very similar to white prunicola scale (Pseudaulacaspisprunicola). Look for small white scales with a fried egg appearance. Host specificity can help identify exactly which pest you have. White prunicola scale feeds on Prunus, lilac, and privet. White peach scale feeds on mulberry, peach, persimmon, red twig dogwoods, and other hosts. In this case it could be either species and it would require a specialist for identification. The life cycles of these pests are similar so the treatment approaches are also similar.
One interesting observation I have had over the last several years is that I just am not seeing much eastern tent caterpillar in my region. I am not sure why this is occurring and wondering if anyone else is noticing a similar pattern. In my backyard I found aphids feeding on Spirea vanhoutteii. Boxwood leaf miner adults are also active in my yard. Look for small, orange flies hovering around plants. Now is the time to protect plants to prevent future injury. I am also seeing rose slug feeding injury on roses in my yard. Look for etching type damage on the leaves and small green larvae feeding on the undersides of leaves. I often see the damage from these insects but find it tricky to find the actual pests.
Un-Fortunei I found some Euonymus ortune (winter creeper) this week while out doing inspections. This plant is on the terrestrial invasive plant rule 312 IAC 18-3-25. When it is found destruction is mandated.
During my travels I also found a rather large group of Prunus americana (American Plum). This small thicket forming tree is a pollinator magnet attracting just about every pollinator you can imagine. I observed honeybees, cellophane bees, carpenter bees, bumble bees, green sweat bees, mining bees, bee flies and multiple butterflies. It’s in full bloom now in southeast Indiana but it will fade over the next week or so.
I have also noticed several new populations of Japanese knotweed in Ripley, Dearborn, and Jennings counties. This is not a plant you want around. If you see it, I recommend trying to treat it ASAP. I’ve seen this run rampant in my home state of New York where it will colonize large stretches along streams. The populations I have seen here seem to be popping up in pastures, roadsides, or along right of ways which makes me think folks managing those areas are the likely introduction point. All it takes is a small fragment of the plant to colonize the new area, which can easily be transported on mowing equipment.
Finally, to the beekeepers, queen production and swarming are in full swing. Just be careful with your marking pens…
This past week has been rather uneventful in the aspect of nursery dealer inspections; however, in one garden center I noticed something of interest on two Pyrus communis Kieffer. Although these fruiting pears are considered resistant to the bacterial pathogen which causes fire blight, Erwinia amylovora; they both displayed the standard scorched leaves and blackened branch tips that create the identifiable shepherd’s crook symptom near the apex of the tree. Fire blight is considered by many experts as the most devastating bacterial disease of apples, pears, and other Rosaceous plants.
The bacterium can overwinter in blighted branches and form fire blight cankers that appear as dark sunken areas with a narrow callus ridge around the outer edge. When spring temperatures are near 65 degrees F, the bacteria will multiply rapidly. There is no cure for this disease, so prevention is the best solution for the management of the disease. Fire blight appears suddenly and spreads quickly causing significant damage in a matter of days, but it takes weeks, months or even years to get under control.
How many insects can you find on one plant? While cleaning up my roses this weekend, I found four different issues. Number one was the ubiquitous rose sawfly. Second was a single potato leafhopper nymph on the same leaf. Third was what is probably European fruit lecanium scale on the stem. And finally, while pruning dead canes I found a rose cane borer – which is a general term for several wasps, beetles, and moths that take up residence in the stems of roses. A couple of the wasps have beneficial qualities (they eat aphids). But the entire group can make a mess of rose canes causing wilting of leaves and breakage of stems. Unfortunately, I dropped this one before I could identify it.
There are a couple of things to learn here. First, my sawflies are not as far along as Ken’s. I watch the southern inspectors’ reports for hints as to when I should be looking for things in my area. Second, of the ten or so rose varieties we have, I found all these pests on Lady of Shallot. Insects have favorite cultivars just like we do, so sometimes you do not have to give up on a particular species to avoid a pest problem – just change cultivars!
