Indiana Department of Natural Resources sent this bulletin at 07/16/2019 12:33 PM EDT
Weekly Review for July 16, 2019
This informal report by the Division of Entomology and Plant Pathology is designed to update the Nursery and Greenhouse industry of insect and disease pests the Division has been encountering on a week to week basis and as a way to give a “heads up” of things to be on the lookout for. 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
Soils are really starting to dry up in some parts of my region. I have seen some significant damage from Japanese beetles during the last week. Damage has been seen on numerous hosts including linden, apple, Kwanzan cherry and even some light damage on dawn redwoods. Every year, bagworm seems to be the most economically important pest in my region.
During the last week, I encountered severe bagworm infestations at one of my nurseries. I have also seen serious bagworm infestation in many landscapes. Host included arborvitae, spruce, white pine, hemlock, Hinoki cypress, Japanese maples, beech, bald cypress. They were all over the place at one location last week. Interestingly, they had excellent control last year and there were not many old bags on plants, but they had an abundance of reintroduction this year. Fall webworm was found on edible apples, but I am not seeing wide spread issues with fall webworm.
Look for webbing at the ends of branches, I also found some type of unknown species of leafminer on Ligularia this week. Interestingly, I have not seen a great deal of leafminer on columbine this year. Cypress twig gall midge was found on bald cypress this week. Look for small, white, cone-like structures on foliage. This pest does not cause severe injury to trees but heavy infestations may negatively affect the appearance of trees. Chemical control is usually not necessary. If heavy infestations occur, it is a good idea to rake up and destroy infected leaf debris in the fall.
Now onto the diseases I encountered. The previous wet weather we had in the past and now the high temperatures are allowing for development of many diseases. Shot hole fungus was found on Yoshino cherry and weeping cherry. Last year, I saw nearly complete defoliation on Yoshino cherry in Monroe County, but so far infection levels do not seem as bad as last year. Look for small leaf spots, and small shot size holes in leaves. I am also seeing a lot of powdery mildew. Host include common lilac, magnolia and dogwood. Look for the white powdery growth on leaves.
Plant resistant varieties when possible. Severe cases of powdery mildew can reduce growth. I am also seeing symptoms of spot anthracnose on flowering dogwood. Look for small pinhead sized spots on leaves. Typically, this occurs early in the year compared to Cercaspora or Septoria leaf spots. Laboratory diagnosis is need to 100% identify this disease, especially at this time of year when multiple species of leaf spot disease could be active on the same tree. I am seeing symptoms of Septoria leaf spot on numerous cultivars of red twig dogwood. This disease is extremely difficult to control on red twig dogwood and they seem to get it every year. Early fungicide applications during leaf expansion may help, but the disease pressure is often so high in hot humid weather that every plant seems to get some level of infection form this pathogen.
Symptoms of Cercapsora leaf spot were also found on black gum. Look for small, pin point, purple leaf spots on leaves. There are many species of Cercapsora leaf spot. Over the years, I have had species of Cercaspora confirmed on red bud, honey locust, sweet gum and golden vicary privet. Cercaspora leaf spot tends to be just a cosmetic issue for most plants. However, last year I had a species of Cercaspora that was causing severe defoliation on yellowwood trees and the necrotic areas on the leaves were very large. Finally, needle cast issues continue to be a problem on spruce, pine and even on Douglas fir. During the last week, I found Swiss needle cast on Douglas fir. Damage from this fungal disease causes development of black fruiting structures on the under sides of needles and premature needle drop on the previous season’s growth.
There was a lot of insect activity last week in Wayne County - from happy little pollinators to ravenous yellow necked caterpillars. Yellow necked caterpillars typically feed in large groups so it doesn’t take long for them to do noticeable defoliation. When you see them huddled together on just a small tree or two, control is as easy as dropping them into a bucket of soapy water.
I didn’t find a lot of things this week but here are some of the highlights.
Daylily leaf miner was pretty wide spread at one of my larger daylily growers. There was quite a bit of it but it wasn’t causing any significant issues for the wellbeing of the plants.
I found a very fat and content catalpa sphinx moth caterpillar. Finding these guys is usually quite easy due to the large amounts of defoliation they can cause. This year, I have found them several times but it's only ever a couple of caterpillars at a time.
I also found my first bald cypress twig galls of the season. There are two generations of this a year. I believe this is the first generation as there are no older galls hanging from this tree. I plan on revisiting this site if I have time to get a photo of the second generation and older galls.
Some of the pest and disease issues that I’ve noted over this last week have been: botrytis blight on peony, cedar apple rust on apple, Japanese beetle on grape and crabapple, “shot hole disease” on weeping Snowfountain cherry, leafminer damage on magnolia and leafminer damage on azalea. I have included a photo of the leafminer damage on azalea.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
Last week, I started seeing a lot of this type of feeding damage on plants on my property including redbud, ash, and buckeye trees. I’ve observed several species of plant hoppers on these trees.
This week, I am at the Cultivate 2019 conference in Columbus, Ohio. I’ve attended some great talks about biopesticides, boxwood blight, SANC certification for nurseries, and new and emerging diseases of ornamentals. I highly recommend this conference for anyone in the nursery and landscape industries - in addition to the wonderful presentations there is a ton of neat stuff at the trade show. It is in Columbus every year.
I attended the Purdue Turf and Landscape Field Day on Tuesday. This event has developed into a well-rounded event covering a lot of timely topics in the industry.
This year, I have had the opportunity to work on storm damage and urban trees. What has really hit home to me is the number of cases where a hazard tree situation could have been corrected with a pair of pruners when the tree was planted or even still in the nursery. Now that I am looking for them, I am stunned by the number of trees I find in nurseries with codominant stems and other characteristics that can lead to future tree failure. Purdue’s Lindsey Purcell has been doing a lot of work on hazard analysis, tree evaluation, and corrective pruning as of late. Check out his articles in the Purdue Landscape Report.
Discolored foliage and stunted growth patterns are still pretty easy to spot in nurseries that suffered flooding injury. Japanese beetles hit hard in a several of my nurseries in Cass, Miami, and Carroll counties. I haven’t seen damage like this in a number of years. I was talking to Dr. Sadof at Purdue at the Field Day about this and he thinks the hard winter from a couple years back was bad enough to kill a lot of the Japanese beetles as well as the diseases and predators that were keeping them in check. The beneficials have lagged behind as the Japanese beetle population recovers, but should come back into balance in a couple years.
I found what looked to be flatheaded apple tree borer damage on Redbud. This pest has a very wide host range and its damage can be confused with winter cracking or mower/trimmer injury. Considerable damage at the root flare resulted in one entire stem dying back. I also saw some significant dieback on maples from oystershell scale.
Beekeepers have been taking off honey the last two weeks. Some are getting a good harvest, others are okay. If they were lucky they were able to get some black locus honey. With all the rain when black locus was blooming it was hard for the bees to get out and get it. The sweet clover did well in many areas of the state. It is just starting in northern Indiana. Sweet clover is done in southern Indiana. I do see bees on Dutch clover in the middle section of the state. With these high temps and dry weather the Dutch clover will shrivel up and stop blooming. The summer dearth should be starting soon. No nectar until the fall flow. The bees will still find pollen, but nectar becomes scarce.
Some beekeepers put honey supers back on so the bees have room away from the brood area. The bees may put more honey it in, but it is mostly to help with overcrowding. In hot weather you may see bees gathering on the outside on the front of the hive. I tell beekeepers to stick a couple of honey supers on top of hive to get bees back in the hive at night. They will stay up there away from the brood.
A few hives still have foundation to be drawn out. Those beekeepers need to feed sugar water to the bees. Keep feeding the bees here in July and they should continue to draw out comb. If you stop feeding now, that foundation will be chewed up and not drawn out. Foundation does nothing for winter bees.
Mid-July is the time when beekeepers should start thinking about what needs to be done to get the hives ready for winter. Get the bees to finish drawing out comb in the equivalent of two deeps. Make sure the queen is laying in both brood boxes. Check for varroa mites and order Varroa mite treatments for August or September application. Also find frames that should be replaced next year and move them to frame position 1 or 10 to make them easier to remove later.
Some beekeepers will do late splits and raise queens in July and August. They take off the honey from a strong hives, split them, and get the bees to make queens. July and August has less rainy days that make it great for queen mating. If you try this, I recommend that you have plenty of drawn comb to give to the splits. Bees do not like to draw out foundation in July and August. It takes a lot of nectar/honey to drawn comb. You would have to feed sugar water and hope they drawn it out.
I am getting in hives at 7 or 8 in the morning to beat the heat. Beekeepers can get in hives as soon as the sun hits the hive. When it hits 90 degrees you start to sweat as soon as the bee jacket and veil goes on. Have plenty of water or Gatorade with you. Bee safe in the heat!
