Indiana Department of Natural Resources sent this bulletin at 06/09/2020 11:54 AM EDT
Weekly Review for June 9, 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.
It has definitely been a slow start this year, but with the weather warming up, things are beginning to move. I’ve seen aphids feeding on Spirea as well as some damaged caused by balsam twig aphid. Damaged from the late freeze is still very visible in a lot of areas, but it seems for the most part that plants are beginning to recover. Bullet oak gall on swamp white oak trees is always a little unsightly, but fortunately it doesn’t cause any real harm, at least on older trees. There are several species of cynipid wasp that cause bullet oak galls on twigs. Old galls can easily be determined by finding the exit hole. The larva are well protected inside the hard galls unless someone breaks into their guarded home.
Moving into the second week of June, frost damage is still the biggest issue I’m seeing. The milder winter and early spring seemed to give a lot of different species a jump start on the season, but the last freeze we had took a toll. Green Giant arborvitae seemed to take a really hard hit. It’ll be interesting to see if/when they are able to grow out of it. I also saw some spittlebug causing damage on various species of goldenrod.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
Some parts of my region have had decent rainfall during the last week. However, other parts, like my yard, have not had a drop. The high temperatures and low relative humidity levels this weekend really took a toll on new transplants. I know I say this every week, but I am not sure where the aphids and mites are this year. I have seen very little damage from those pests. Bagworm should be emerging soon. Catalpa trees are beginning to bloom, but I have not seen any active bagworm so far this year. I found low levels of oak bullet gall on white oak in Lawrence County. It appeared to be last year’s damage. Some areas in Sullivan County have serious problems with galls on oaks. Typically they are not a problem, but heavy infestation can cause dieback. There really are not any good controls available to control the Cynipid wasps that cause the galls. I also found oystershell scale on red maple. This pest is occasionally found in the nursery industry. Heavy infestation can kill branches.
Cedar apple rust and apple scab are continuing to be a problem on many susceptible cultivars of crabapple and edible apple. I have included another picture this week for your viewing pleasure. I had a garden center contact me stating that they had rust on their roses. I said that I had never seen that before. However, last week I found rust on roses in Putnam County. Never say never. This is the first time this has been found in Indiana. Samples have been sent to Purdue University for identification. Apparently there are 10 different rusts that can infect roses. We do not often see the problem here in Indiana. This is a new one for me, and I will keep you posted on what I learn.
I am continuing to find needlecast problems on Eastern white pine and Japanese red pine during the last week. This year I have had Diplodia, Dothistroma pini, Lecanosticta acicola, and Ploioderma all confirmed on Eastern white pine. Infections have been found primarily in forested areas, but there have been a few infected trees found in nurseries as well. Lophodermium was another needlecast was confirmed on Japanese red pine during the last week in a garden center. Needlecast diseases cause previous year’s growth to turn yellow and brown and fall off, often leaving only new candles remaining. Look for small brown fruiting bodies occurring on the needles. In some cases, you may not see fruiting bodies if the relative humidity levels are too low. Field identification is not really feasible to identify the exact species of needlecast. One interesting thing about needlecasts is that the damage you are seeing this year is a result of infection that occurred last year. New growth must be protected with fungicides to prevent new infection.
I am also finding some cultural problems in the nurseries at this time. Numerous trees such as Norway spruce, white pine, oaks, deciduous holly and Itea have symptoms of iron deficiency. Look for interveinal chlorosis on the leaves. This is an indication of a micronutrient deficiency, and it typically is iron when this symptom is observed. I am also seeing herbicide injury in some nurseries. Be careful when spraying around trees. Make sure individuals spraying in your fields have adequate training. You may not see the damage from misapplied herbicides right away, but it can affect the plants’ growth for multiple years. Herbicide injury can cause leaf yellowing, stunting and bark splitting, depending on the type of product applied.
