Indiana Department of Natural Resources sent this bulletin at 05/26/2021 07:20 AM EDT
Weekly Review for May 26, 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
Cicadas are the big insect in the news right now. However, I am not seeing as many as I thought I would in my region. There are pockets of cicadas in the Bloomington area, but on May 21 I was only able to find a few crawling around in Brown County and on May 23 I was not able to find any adults in Summit Woods on the southwest side of Bloomington. Cicadas seemed to be more abundant in 2004. I have not seen a single adult in my new subdivision because the soil was disturbed after 2004. Hopefully I will find a few more spots I can take my son to so he can hear the noise.
I am starting to see more pest problems this week. Aphids are becoming abundant on many ornamentals such as Spirea, Aronia, bee balm and Asiatic lilies. I also found woolly birch aphids on river birch. Look for leaf cupping, sooty mold and whitish aphids on the undersides of leaves. Large populations can be unsightly to customers, but this pest typically does not cause serious injury to river birch. I also found oyster shell scale on ‘Jane’ magnolia. Look for small, grayish elongated scales that look like oysters. Japanese maple scale can look similar but is usually whiter in appearance. Control of oyster shell scale can be aimed at the crawler stages and is typically active in June. When I encounter this pest it typically heavily infests one or two trees at a time. It may take some time to clean up infested trees, but large populations can cause branch dieback and tree death. I am also starting to see redheaded flea beetle activity at a few locations. Look for holes in the new growth of susceptible host. Itea, red twig dogwoods and Hydrangea paniculata seem to be their favorite. Sometimes if you lucky you can find the adults that hop when disturbed.
During this week I found ambrosia beetle activity on Kwanzan cherry in Lawrence County. Look for frass toothpick-like structures coming out of infested hosts. There are several species that can make these types of damage. These pests will go after both healthy and stressed hosts. Ambrosia beetles look similar to bark beetles in size and are typically 1-2 mm long, but they will bore deeper into the wood compared to bark beetles, which exist just underneath the bark. Residual and/or systemic insecticides such as permethrin, bifenthrin and systems such as imidacloprid may provide protection from this boring insect. If you see this on sassafras, please contact the DNR immediately because there is a new exotic species of ambrosia beetle called Xyleborus glabratus which is moving a fungus that causes red bay mortality in avocado, sassafras, and spicebush. This disease was recently found in Kentucky and we are looking for it in Indiana. If you see wilting sassafras or evidence of ambrosia beetles in sassafras please contact the DNR.
I am also starting to see more disease issues. I haven’t seen any fire blight yet, but I have observed numerous leaf spots diseases during the last week. Leaf spots are beginning to develop on oakleaf hydrangea. These leaf spots can be caused a result of fungal or bacterial infections. Leaf spot on oakleaf hydrangeas are very common, but I never have seen serious leaf drop caused by infection of leaf spot disease on this plant. I also observed leaf spot on iris which was thought to possibly be Didymelina leaf spot. As always, laboratory diagnosis is needed to confirm the causal agent of the disease.
Powdery mildew was also found on numerous hosts this week. It seemed to be particularly heavy on drift rose, and I even found several infections on Spirea to the point that the leaves were developing a reddish color. Susceptible cultivars of Phlox paniculata are also becoming infected with powdery mildew. Botrytis was found on gerbera daisies in garden centers. Botrytis is typically a cool, wet, weather disease but can continue to be a problem if plants are inadequately spaced and overhead watered daily. Look for grayish fuzzy growth, especially on bottom leaves. Close examination of this growth will reveal grapelike clusters of spores and this can typically be viewed with a hand lens. In some cases, severe infections will move from leaves to the crown of the plant and result in plant death. I also found symptoms of Nectria canker on lilac. Look for dieback and orange sporulation on infected areas. This is typically a secondary pathogen that often can infect plant tissue that was damage from adverse environmental conditions such as freeze injury or drought.
Last but not least, there are cultural issues. Plants are flying off the trucks and getting stacked into the garden center. Things are often very crowded in the spring and we need to get the plants off the trucks ASAP so we can go back to assisting customers and clients. However, don’t forget to make sure your plants have adequate spacing. It may be time to go back and evaluate spacing in your garden center. Some plants will tolerate this while others will develop disease issues from reduced air circulation. Pay particular attention to Alberta spruce. If they are placed too close to each other, you will get yellowing and branch dieback. This may also be a good place for spruce spider mites to get started.
I have not come across many insect or diseases problems during my nursery dealer checks and greenhouse inspections. The insects I have come across include thrips on various annuals such as gerbera daisy, ostesperum, calla lilies, zinnia, cleome, peppers, and tomatoes. Spider mites were found on tomatoes and spikes. Diseases that I found were Botrytis blight on New Guinea impatiens and begonia. I also found Septoria leaf spot on oakfleaf hydrangea and red twig dogwood.
I came across one group of gerbera daisy that showed virus symptoms and sent some pictures into Purdue Plant and Pest Diagnostic Lab. They confirmed it was a virus and most likely a tospovirus. I wanted to send a plant to the lab for a confirmation on the type of virus but the owner had already disposed of the suspect plants.
As I drive around, I have noticed that the sycamore trees are really struggling and the disease culprit is most likely sycamore anthracnose.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
This week I saw an elm tree in the landscape in Hendricks County absolutely covered in European elm scale. The trunk, branches, and leaves were sticky with honeydew and the trunk was blackened from sooty mold. Periodical cicadas have appeared in my yard in Marion County the last few days. I have seen the exuvia (shed exoskeletons) for a couple weeks now here and there, but it has really ramped up the last few days. I saw about 50 adult cicadas in my yard this morning. The division has been getting a lot of calls about cicadas, including people from other states wanting to travel to Indiana to see them and wondering the best time and place to go to see them is. We also get asked about “albino cicadas” occasionally. The whiteish cicadas people are seeing are actually freshly emerged adults whose exoskeletons have not hardened after molting. They will darken to the regular pigmentation soon after.
Most of my dealer inspections in the last week have revolved around trace forwards, but I am still occasionally seeing plants for sale that are prohibited by 312 IAC 18-3-25, the Indiana Terrestrial Plant Rule. Indiana licensees and their suppliers should both be aware the rule is in full effect. A complete list of plants can be found on our website.
The periodical cicadas Brood X have definitely made an appearance in Perry County. There are several reports of emergence in Perry County and of people seeing and hearing cicadas in the trees. It’s starting to get loud down here!
I have seen a couple of abiotic (non-disease) disorders over the past few weeks. The first is sunscald on bromeliads from greenhouse temperatures getting too hot and plants too dry. The second is a purple physiological spotting that can occur on gaura during cooler growing temperatures.
More honey supers need to go onto hives. If the honey supers have drawn comb, I would suggest having three or four supers on hives right now. If there is only foundation, put two supers on and watch closely to see what the bees do. And do not forget to put honey supers on some of your captured swarms.
I am seeing lots of nectar being stored in the brood boxes. Beekeepers may need to switch out some of the frames of nectar for a new foundation for the bees to draw it out and let the queen lay eggs on it. If the frames are capped honey, extract and stick the frame back in. That will help with giving the queen room to lay.
Checkerboarding frames can be done easily now. I go by warm night temperatures, not day temperatures. Once nights are in the mid to high 50’s we can easily break apart the brood area. Checkerboarding is where you stick a frame of foundation between two frames of drawn comb. It is usually done in the brood boxes. The bees are usually quick to draw it out and allow the queen lay in it. You can checkerboard the honey boxes, but the bees can be slower on drawing out the comb. They already have comb to fill up with nectar, so they will not draw the foundation until they need the room.
Foundation type matters when putting on honey supers. Use all plastic foundations in a honey super. If you mix plastic and wax foundation, bees tend to draw out the wax foundation before drawing out the plastic. Always make sure that the plastic is coated with wax. Bees draw off the wax that is on the plastic.
Why use a plastic foundation? When extracting honey, the plastic is strong enough to withstand spinning. If the wax foundation is not wired correctly, spinning it too hard can pull the comb out of the frame. The comb literally blows apart, separates from the frame, and falls in chunks down to the bottom of the extractor. You also just ruined drawn comb that took the bees a lot of energy to produce.
