Indiana Department of Natural Resources sent this bulletin at 06/04/2020 09:12 AM EDT
Weekly Review for June 4, 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.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
The pest season is slowly coming to life. However, I have not seen spruce spider mites or maple mites so far this year. I do not know where the mites are this year. So far the only mite I have observed has been the two spotted spider mite on greenhouse grown crops. I am occasionally seeing aphids on apple and Spirea, but population levels are not large. I am starting to see leafhoppers on red maple. Look for coarse stippling damage on the leaves and small pale nymphs or larger adults on the undersides of leaves. Leafhopper feeding can causing stunting of growth on red maples, but they can be difficult to control since they are abundant.
I have been getting some phone calls about ambrosia beetle damage to trees. Ambrosia beetles are small beetles that bore into the wood of host trees. One common species is the granulate ambrosia beetle. Look for small, toothpick-like projections protruding from the trunks of trees. They primarily attack deciduous hosts. During recent inspections I found ambrosia beetle damage on mimosa trees that had serious winter injury. There are several ambrosia beetles that can make the toothpick-like frass tubes, granulate ambrosia beetle (Xylosandrus crassiusculus) being one of them. They can infest any deciduous species, but tend to go after stressed trees. Attacks on healthy hosts, however, have been reported.
Tulip tree scale was found on tulip trees in Monroe County. This soft scale has a crawler stage that occurs in late summer while most other soft scales have a crawler stage that occurs in June. Immature tulip tree scales can be found on both tulip trees and magnolias this time of year. They look black, with a small amount of orange in the center. As they mature, the amount of orange color increases on them. They can also produce a large amount of honey dew which is followed by black sooty mold growth. I am also starting to see damage from white pine weevil on Norway spruce and white pine. Look for wilting and dying leaders. At this point you will need to cut out infected leaders. Control efforts should be conducted early in spring on adults before they lay eggs. Finally, on the insect side of things, I am seeing low levels of maple petiole borer damage on red maple. Look for tip dieback on new growth with hollow centers. The damage from this pest is usually on a minor issue.
As an entomologist I am a bit disappointed. So far it seems to be more of a disease year than a pest year. However, there is plenty of time for that to change as the growing progresses. Cedar apple rust is abundant on numerous hosts. I even found a species of rust on pear trees that were shipped from Oklahoma. This is not cedar-apple rust but another species. Rusts on pear are not common, but do exist. This was a new one for me. I am starting to see apple scab, primarily on edible apple species. Not much on crabapples yet. On flowering dogwoods, I have seen spot anthracnose but no symptoms of Discula anthracnose so far this year. Spot anthracnose looks like small pinhole-size purple lesions. This disease can leave foliage looking unattractive but is not the severe threat to dogwoods that Discula is. I also found symptoms of Nectria canker on mimosa trees that had severe winter injury. This fungus often appears as orange growth on the bark of infected hosts. It is often a secondary disease. I do not often see this in the nursery industry. I saw a heavy infection of leaf spot on newly planted English Hawthorns. I often see this plant heavily infected with leaf spot to the point it gets early defoliation. In the past I have had Entomosporium confirmed on this host, but lab tests are needed for 100% identification. I am seeing symptoms of what appears to be root rot on white pine. Look for trees that have an off-green color and new candles that are wilting. In some cases, trees may not even start new growth. This is often a problem in nurseries that have heavy clay soils. There is not much that can be done other than plant white pines in a different part of the nursey. Trees with root rot often get bark beetles as a secondary problem. It is best to just remove these trees for sanitation purposes.
Winter injury is common in a lot of our landscape and nurseries right now. As things are warming up, we can see the damage that has been caused by fluctuating temperatures. Really, this damage should be more appropriately called spring freeze damage. The winter did not do a great deal of damage, but the three freezes we had this spring have outright killed some ornamentals. I am seeing quite a bit of cold injury on Chamaecyparis. Green giant arborvitae have made it through severe winters here in Bloomington, but this year I am seeing significant cold injury that occurred after these plants greened up and then got hit by multiple rounds of temperatures in the 20s. It is not just the ornamentals that got hit hard by the freezes. Until about a week ago, there were parts of the Hoosier National Forest that were still bare because of the freeze damage. Oaks, tulip poplar and even black walnut suffered significant freeze injury this spring. My fringe trees got severely damaged but are coming back out of it. One plant that surprised me was my Japanese tree lilac. This is one of the first plants to leaf out in the spring. The fully expanded leaves made it through three nights with temperatures in the 20s and did not receive any noticeable damage. This surprised me because many native plants that I thought would not get freeze injury did, but the Japanese tree lilac did not. I hope to have more goodies next week.
I saw some new, old problems this week. First up is rosy apple aphid on red delicious apple. This pest was introduced sometime around 1870. This is the most serious apple aphid and left unchecked can cause quite a bit of damage. Typically you will find curled leaves, which hide the aphid colony and also help protect the developing aphids from control measures. Left unchecked, this aphid can cause extensive shoot deformation. Rosy apple aphids feed on apple and pear in the spring and then move to broad and narrow leaf plantain during the summer and then back to the apples to overwinter. This is done through multiple generations with both winged and non-winged forms of the aphids.
Another find was some San Jose scale on apples also introduced somewhere around 1870. This is the pest that was the cause for the creation of the DNR Division of Entomology. Again, left unchecked, this pest can cause quite a bit of dieback and in this case has caused the shoot tip on this branch to begin to decline. This is a pest that can be extremely hard to find due to its small size, which makes it easily overlooked.
Finally, the most interesting find for me was right in my backyard. I was walking out to take a look at my 3-year-old volunteer ash transplant that I dug out of my field and put in my yard when I noticed one of my pussy willows starting to yellow. While I was standing at the willow looking at the foliage I caught a whiff of quite pungent fermentation. Upon further examination I found the lower stem to be riddled with holes and quite a bit of frass accumulated around the base of the shrub. This particular willow was a goner, so I decided to do a post mortem. The culprit responsible was the willow poplar borer, which was first discovered in New York in 1882. This is a weevil with an affinity for willows and, to a lesser degree, poplar and alder. This is a serious pest of willows in the wild and has been reported as a serious nursery pest but is not one that I have run across frequently.
Now that the weather has warmed up, there have been many reports of hives swarming over the last two weeks in southern and central Indiana. Northern Indiana should be getting swarms next week.
Two hives I looked at today in Martinsville had swarmed. The hives contained no eggs, mostly capped brood and lots of queen cells. When I pulled a frame out, it cracked the top of a queen cell on a frame below. We could see a queen moving in the cell. By the time we were finished looking at the frames above her, she had chewed her way out and down into the hive.
Beekeepers need to get honey supers on hives. The largest nectar flow for Indiana is in June. Strong hives that wintered over may have several honey supers on by now. I have seen bees capping honey over the last two weeks. When I see them capping honey, I like to put another honey super on to give them more room to store nectar.
A hive that swarms and is waiting for a new queen will keep collecting nectar and put it in the brood area, leaving little room for the new queen to lay eggs. Beekeepers have a few options. The first option is to replace frames that consist of all nectar or pollen with new foundation or drawn comb. Second, the beekeeper can remove a frame of honey, extract it, and put the frame back in the hive. The new queen can find that frame and start laying. Finally, uncapped nectar right now is wet. The frames can be shaken to remove the nectar and replaced to make room for the queen.
