Indiana Department of Natural Resources sent this bulletin at 07/09/2019 08:25 AM EDT
Weekly Review for July 9, 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.
It has been a crazy year so far, but I was finally able to begin inspecting nurseries in Wells and Allen counties this past week. I found tar spot beginning to develop on Norway maple and red maple. On the Norway’s many of the spots I observed were just yellow but I did find one tree that was beginning to get the black speckling within the yellow spot. Apple scab was pretty heavy on susceptible varieties of apple and crabapple and it was also showing up lightly on resistant varieties.
Septoria leaf spot was heavy on ‘Ivory Halo’ dogwood and there was moderate powdery mildew developing on a few varieties of Phlox as well as ‘Cherokee Princess’ dogwood. Cedar quince rust was affecting the stems and fruit of serviceberry and various leaf spots were found on Hydrangea, horse chestnut and black eyed Susan.
I observed moderate to heavy oystershell scale on ‘Autumn Blaze’ maple, red maple and sweet gum. Several branches were beginning to die back on several trees due to their feeding. Potato leafhopper was injuring many varieties of red maple as well as ‘Autumn Blaze’ maple. Spidermites are becoming more active now that it’s gotten warmer and drier. I found light infestations on honeylocust, as well as red maples.
Most varieties of red maple had light infestatons with the exception of ‘Brandywine’ which were moderate. Red headed flea beetle was causing light to moderate damage on a variety of plants including numerous varieties of Hydrangea. Other pest problems I observed included maple bladder gall on ‘Autumn Blaze’ maple; Japanese beetle on chokecherry, willow and Hibiscus; birch aphids on river birch; plant bug on honeylocust and moderate to heavy leaf galls on ‘Gro-Low’ sumac.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
I do not have a great deal to report this week because I was on vacation. Japanese beetle are active in my region, but so far I have only seen light damage from this pest. During the past week I found aphids on swamp milkweed. I also found milkweed bug on swamp milkweed. Look for orange and black bugs feeding on stems. They tend to be shy and will hide from you when disturbed. Milkweed bug looks very similar to boxelder bug except the color pattern is reversed and there is more orange visible compared to boxelder bug. Boxelder bug will feed primarily on boxelder. Damage from milkweed bugs and aphids on milkweed is usually not very serious.
I also found a common lilac that was severely infested with clearwing borers. There are two clearwing borers that can infest lilac: The ash/lilac borer which have adults that emerge in early summer and the banded ash clearwing borer which has adults that emerge in late summer or early fall. Look for round exit holes and branch dieback. If you get lucky you may be able to find brown pupal skins near the exit holes, though they are often blown off of infested plants. Control can be difficult. Protect healthy stems with a residual insecticide and prune out infested canes during winter months. If the plants are healthy enough, new growth and new stems may emerge the following year, but realize that the plant is still under stress and susceptible to additional borer infestations.
My vacation was in southeast Maine. I was mostly along the coast south of Portland and I was surprised to find some plants growing in landscapes that I did not think would make it that far north. Japanese umbrella pine (Sciadopitys verticillata) was doing quite well in that area. I was also surprised to see Kousa dogwoods that were well over 25 feet tall. The specimens I observed in the Kennebunk, ME area were nearly as large as the prized specimens that are at Longwood Gardens in Kennett Square, PA.
Mountain laurel and Leucothoe also were performing quite well in landscapes Japanese maples also appeared to be doing quite well. The winter temperatures in Kennebunk are about the same as Indiana, however winters there are much wetter with very large snowfalls. Large snowfalls are likely providing some protection from winter temperatures. Lupines were blooming along road sides and I also found some type of iris growing along the rocky cost north of Portland.
The weather has not been good for the plants this year. Between the cold winter we had and the cool, rainy spring and early summer I have noticed a lot of environment stress and damage. I have also noticed quite a bit of fungal leaf spots, Apple scab, powdery mildew on Lilac, Coral Bells, Garden Phlox, Roses, etc. I have noticed Four-Lined Plant bug on Hydrangeas and Weigela, Potato Leafhopper on Red Maples, Oak slug Sawfly Damage on Swamp White Oak, slug damage on hostas, and Azalea Lacebug on Azalea. I have seen Japanese Beetles flying around but I didn't see any feeding where I was inspecting.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
First off, a correction on my last Weekly Review entry. I previously posted a picture that I thought was woolly aphids, but it turns out they were actually planthoppers. I read a timely article by Joe Boggs in the Buckeye Yard and Garden onLine blog (BYGL) about plant hoppers last week with great pictures and descriptions explaining the differences. My coworker Ken also caught the error, thank you to him as well.
Last week, I only had time for a few short inspections. I continue to see tiny bagworms, especially on white pine and arborvitae. I also have been seeing white pines with wilted tops and shepherd crooks indicative of white pine weevil. I cut one of the terminals open and found tons of larvae and chip cocoons.
I have included a couple of photos of a rust disease on ‘White’ Rose-of-sharon. One photo shows the underside of the leaves with erupted rust pustules and the other photo shows the discoloration symptoms visible on the upper surface of the leaves.
This past week, I saw my first real accumulations of Japanese beetles near Indianapolis. They were feasting on elms, crab apples and weeping cherries. Strangely at my house, where I have endured nearly complete defoliation of my apples almost every year for the last 4-5 years, I only have a handful of beetles. I saw my first wilting of a leader on a Norway spruce by white pine weevil. To confirm weevil damage peel back some of the bark just below the wilting to expose the damage by the weevil larvae. In this case I could not find the larvae but the frass is a telltale sign that they were there.
I find that spruce wilt slower than the white pines and they also don’t produce a pronounced shepherds crook like the white pine. It’s always a good idea to take a second look at a tree even if you think you know what the problem is. From afar bag worm injury can be mistaken for Japanese beetle damage, especially after you have looked at tree after tree with hundreds of beetles on them. I found oyster shell scale at one location last year on newly transplanted whips. At the time the scale was limited to a few trees and only causing some very light tip dieback. The trees were not treated last year as I had recommended. This year it was hard to find a tree without some scale on it and a good 10-20% of the trees were showing extensive dieback on branches and some were already dead.
So, I included a rather normal looking photo of an oak canopy. If you look hard, you might see some branch tip dieback. There were a few shot holes here and there. And if you really hunted, you might find a few Gypsy Moth caterpillars. One year ago, there wasn’t a leaf on those trees! This year is turning out to be tough on GM. The cold winter did a decent job desiccating the egg masses. Meanwhile, the rain has promoted fungal and viral disease further limiting the populations. Adult flight seems to be delayed this year as well, so you will probably see our GM traps out longer than normal this year.
I have a few Christmas tree farms and I’ve noticed heavy numbers of cones on Fraser fir, among others. These cones should be removed early in the season for two reasons. First, they take a lot of energy away from the growth of the tree. Second, when the cones fade in the fall, unsightly gaps in the foliage can develop. In many trees, heavy cone or seed production is a result of heat, drought or other stress on the trees in late summer of fall when buds are developing on the new growth.
In the nurseries, I am still starting to see light populations of maple mite popping up here and there along with potato hopper damage. The two-marked treehopper on redbuds is always a cool find when I can catch them. There seemed to be an abundance this year, but they cause little damage.
Diseases are becoming more easily found. Tar spots and powdery mildews are the two most common I am finding. I am still seeing a fair amount of sycamore and maple anthracnose damage out there, though the trees are well on their way to recovering from those early season problems.
