Indiana Department of Natural Resources sent this bulletin at 07/30/2019 08:39 AM EDT
Weekly Review for July 30, 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.
I didn’t find anything unusual during inspections last week. Tar spot was found on silver and ‘Autumn Blaze’ maple. Powdery mildew was light on privet and plane tree, and moderate on Magnolia. Black knot was heavy on ‘Canada Red’ cherry and apple scab was moderate on many varieties of crabapple. Yellownecked caterpillar was present on bur oak. Smaller trees can be completely defoliated by this pest, but larger trees typically have defoliation on single branches. Redbud leaf folder caterpillar was found on several redbuds at one nursery in Allen County.
These caterpillars fold over a leaf and stich it together which protects them from pedators while they feed. Japanese beetle is still causeing damage on a variety of trees and shrubs and I saw a few apple trees that were severely damaged. Several river birch trees at one nursery had heavy leaf galls caused by Eriophyid mites. Red headed flea beetle was causing damage on ‘Lime Light’ and ‘Sweet Summer’ Hydrangea and spidermites were present on serviceberry, oak and maple. I also assisted on an inspection in southern Indiana and we found a molting wheel bug.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
I do not have much new to report this week. During the last week I observed severe cedar-quince rust infections on Washington hawthorns. Look for large stem galls with orange spores emerging from infected tissue. This symptoms of this disease look terrible, but it never seems to kill infected trees. Hawthorns are frequently infected by rust every year.
I also observed nutrient deficiency on red maples. Interveinal chlorosis on plants is an indicator of a micronutrient deficiency. On red maple is frequently manganese deficiency, but could also be an iron deficiency. In order to 100 percent identify nutrient issues both soil tests and leaf tissue analysis should be conducted. Nutrient deficiencies can be correctly by making the nutrients more available by adjusting soil pH or by adding nutrients to the soil to make them more available for your plants. Water quality of irrigation water can also affect nutrient uptake. It is a good idea to know the quality of the water that is being put on your plants. Especially when summer time temperatures increase the need for irrigation in containerized plant material.
Over the last 10 years, I have watched numerous blue spruce trees decline in my region. Rhizosphaera needle cast has been confirmed on many samples. Two other fungi have been found on blue spruce in my region. Stigmina lautii and Setomelanomma holmii (SNEED, Sudden Needle Drop) have also been confirmed on blue spruce in my region. For years, Serbian spruce, White spruce and Norway spruce seemed to be immune to this problem. However, in the last 3 years this seems to be changing. I have a Serbian spruce that has confirmed for the presence of both Rhizosphaera and Stigmina. This tree is slowly declining in my yard. I have also found Rhizosphaera on white spruce and Canaan fir in my region in the past 3 years. One of our inspectors has also found low levels of needle cast disease on Norway spruce but I am not yet seeing wide spread decline. This year, with asstiance from Purdue University, we were able to confirm a needle cast fungi, Dothistroma pini, on white pines in Monroe County. This is the first time we have found needle cast on white pine in Indiana. I have not observed this issue in the nursery industry. It has been primarily in forest areas and plantations located in Bartholomew, Brown, Owen, Morgan and Monroe counties.
Recently, I noticed a large Norway spruce declining in my area. From a distance this tree was thinning and appeared that it may have a type of needle cast disease. However, upon closer inspection I could not find any symptoms of needle cast or spruce spider mite injury. All of the inner needles on the tree had already dropped off and I was not able to get any decent samples. I will continue to monitor this tree for symptom development. It could be something abiotic causing the decline. Other states have reported needle cast disease on Norway Spruce, but I have not seen it as a wide spread problem yet. However, I am concerned that this may be changing. I hope I am wrong.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
A couple weeks ago I saw a whole crop of dwarf inkberry holly with pretty bad stem-girdling roots. While some species of plants may be more predisposed to girdling roots every individual plant had this issue leading me to believe it was caused by poor planting practices such as leaving plants in too small of pots for too long, or wrapping the roots when planting to make them fit in the pot. Over time, this issue can prevent the flow of nutrients and water up and down the trunk and weaken the structural integrity of the plant. Eventually, the plant may die as a result of stem-girdling roots, so these roots should be cut prior to planting to allow the trunk to grow.
I was on vacation in northern Minnesota last week where I got some serious hands-on time with heavy spotted wing drosophila in raspberries. It doesn’t take long for this critter to turn fruit into mush! I also had the much more pleasant experience of sitting under a real, living ash tree. But you can bet I was looking for signs of EAB.
Red headed flea beetle has really made its mark in certain places. Some weigela have been totally hammered with more moderate damage occurring on a wide range of other species including sedum, viburnum, forsythia, and sweetspire, among others.
Some of the leaf diseases have progressed nicely with this bout of heat we have had. Apple scab is hitting its peak and the tar spot on my silver maple seemed to come out of nowhere.
One interesting find during an inspection this week was a group of forsythia that looked like the growing tips had fire blight. Now with forsythia being in the olive family and fire blight only affecting the rose family, this can’t be. We have a couple guesses as to what might be going on, but a sample is going to PPDL for verification.
