Indiana Department of Natural Resources sent this bulletin at 04/29/2020 10:03 AM EDT
Weekly Review for April 29, 2020
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.
Welcome to the first regular issue of the Weekly Review for 2020. Please feel free to pass this report around. Subscription information and past issues can be found here.
First, the Covid-19 situation has altered our operations as much as they have altered yours. Our division is still operating. We are doing our best to handle necessary site visits in a safe and effective manner. In the meantime, please don’t hesitate to call or email your inspector if you have any questions or concerns.
Second, we would like to remind everyone that the Terrestrial Plant Rule (312 IAC 18-3-25) went into effect April 18, 2020. This rule prohibits the sale, trade, or distribution of 44 species of plants. The rule and a full list of species regulated can be found online. And yes, we are enforcing it.
The biggest thing I have noticed in nurseries is inadequate frost protection. We have had freezing temperatures several nights over the last week or so. I’m seeing damage primarily on boxwoods from Oklahoma. This damage is going to make scouting for Boxwood Blight more difficult this season. I’ve also seen damage to the tips of some fruit trees and other shrubs. Thrips are starting to become a problem in a few greenhouses I have visited as well.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
The pest season is off to a slow start this year. I still have not seen any eastern tent caterpillar activity in my area. Not sure if the numbers are low this year or if they are just running that late. I have had an abundance of freeze damage in my area to many ornamentals. On my property I received severe freeze damage on my Acer palmatum var. dissectum ‘Crimson Queen’. I am not sure if this Japanese maple will come out of it. The Blood Good Japanese maples seem to be okay because the buds were tight enough that they did not get severe freeze injury. Interesting my Tamukeyama cutleaf Japanese maple also avoided freeze injury for the same reason. Other plants on my property that received severe freeze injury included, Astilbe, toad lily, big leaf hydrangeas, Hostas, Miscanthus sinensis, Bleeding hearts, Japanese forest grass (Hakonechloa) and Green Mountain Boxwood. My Green Velvet boxwoods were not damage because their buds were still tight.
Boxwood leaf miner is actively feeding on the inside of boxwood leaves at this time. Look for a bumpy appearance on the undersides of leaves. The insect is actually a midge that will infest the new growth of boxwoods during leaf expansion. Typically early May, but it may be a bit later this year. In severe cases, like the one in my back yard, blotch mines will coalesce to cause necrotic regions. Treatment should be aimed at preventing adults from laying eggs and preventing the development of larvae from developing in leaf tissue. It is too late this year. Larvae are beginning to pupate and have caused most of their damage already. Damage usually occurs in spring and fall. Right now you can look for the bumps on the undersides of leaves and the formation of small clear areas in the centers of those bumps called pupal windows. If you split infested leaves open you will see an orange larvae or pupae on the inside of the leaf. If the pupal window are clear, this will indicate that adult emergence is coming soon. Yellow sticky cards can be used to detect orange, flying adults which often swarm around boxwood plants in spring.
I am not seeing many insect pests during inspection at garden centers right now. However, I am starting to see some disease issues. During the last few weeks I have seen black spot on roses. I have also seen powdery mildew on roses and columbine. It is really too early to see these problems in our landscape environments and it is highly likely that these problems were shipped to Indiana. Powdery mildew was found on columbine. Rose mosaic virus (A complex of viruses) was found on Queen Elizabeth and Mr. Lincoln roses this week. I am also seeing viral symptoms again this year one weeping Yoshino Cherry. This problem has been found in other states that have confirmed the virus as American Plum Line Pattern Virus. We repeatedly see this issue being shipped into the state year after year from the same source. I am also seeing some dieback on Vinca minor. This plant often has low levels of dieback that can be caused by several fungi. Two that I can remember off the top of my head are Phomopsis and Rhizoctonia. Low level infections can be removed and controlled by pruning. Laboratory diagnosis is required to determine the exact causal agent. Both species have the same symptoms in the field. During an inspection I came across some dead white pine trees. Further investigation revealed the presence of a canker infecting the trees at ground level. There were only 3 trees affected so they were destroyed. I have seen cankers on larger white pines, but never on seedlings this young.
Finally, I love my Yoshino Cherry in my backyard. However, during the previous two growing seasons, I have had early season, complete defoliation of the tree in my yard due to shot hole fungus infecting the leaves. Interestingly, I already found evidence of this on Yoshino Cherry trees shipped from Oklahoma. Look for leaf spots that cause small round spots where the tissue later falls out of the center looking like a small hole. Early instar caterpillars can also cause this type of damage. It will be interesting to see if we encounter severe defoliation again this year. I planted my Yoshino cherry for both the flowers and shade, but late summer shade has been nonexistent due to early season defoliation.
Freeze injury in southern tier counties below U.S. Hwy 50 occurred the week of April 20. The damage may not be noticeable to all trees since they were just leafing out and leaf size was under 1”, if that. So some green tip buds may have turned black and now are re-leafing. Some newly formed maple seed (samaras) were also turned black. Thus, this may not be much damage and is likely only in frost pockets.
Only received two reports of Eastern Tent Caterpillars. The one from Angela in Perry County and the other from Monroe County. My limited travels prevents me from seeing any tents. With the size of caterpillar Angela reported in Perry County, they may complete feeding before black cherry can get their leaves out.
Been getting out and doing some apiary inspections on the warmer, sunny days. Hives that wintered over are building up fast. Beekeepers need to get honey supers on. Some hives may need two honey supers. Nectar is coming in and the bees need room to put the nectar somewhere other than the brood area.
Packaged bees have come in already. I was telling beekeepers if it is going to get real low temps like last week, you could wrap hives started with packaged bees. Tar paper or foam board wrapping will keep the warmth in. So far I have no reports of hives lost due to the cold temps. I looked at two hives started with packages on Wednesday. Both were strong and building up fast.
A beekeeper in Milan, Indiana reported that they collected a swarm. Hives I have inspected in central Indiana are strong, but I have not seen queen cells started yet. When you see queen cells start, you can split the hive and put the queen cells in the queenless split. That should help prevent the old queen from swarming. You can split before there are queen cells if you purchase a new queen. I like to find the old queen and move her with the new split and put the new queen in the original hive. Sometimes you cannot find the queen so make sure the frames you move do not have the old queen on it and make up your new hive.
Friday, April 24 I checked some hives that had sure signs of pesticide drift kill. The nearest field that had been worked was 1 ½ miles southwest of the apiary. The wind on Wednesday was out of the southwest. Lots of dead bees in front of the hive. Killing foraging bees at this time of the year puts hives back at least 2 to 3 weeks on build up. The brood was ok. The bees in the hive look well. Another beekeeper called Thursday night with a bee kill also. This is his second time of getting a bee kill in 3 years. Both are on DriftWatch.
For pesticide drift kills, beekeepers need to contact the Indiana State Chemist Office to investigate. They will be able to do the testing of the bees, take swab samples from the hive and see what pesticides are found. Once the beekeeper gets the report back he can try to find the farmer nearby and talk to him about his bee kill. The Investigations Office can be reached at 765-494-1582 (Map of Investigators).
Corn planting causes the biggest pesticide drift we get at this time of the year. When planting corn, some of the neonicotinoid on the seeds can be rubbed off and end up in the dust cloud behind the planter. If the wind is strong enough it can drift several miles.
