Indiana Department of Natural Resources sent this bulletin at 05/22/2018 12:56 PM EDT
Weekly Review for May 22, 2018
Indiana Department of Natural Resources Division of Entomology & Plant Pathology Phone: (317) 232-4120 Our Website Inspector Territories
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.
Links can be found at the bottom of the page to manage your subscription to this list. Comments and questions about this report are welcome and can be sent to Eric Biddinger or to your respective
Inspector.
The second Bt application for Gypsy Moth should be applied this week, weather permitting. Mating disruption treatment blocks in Marshall County are scheduled for some time around June 22.
One of the more interesting critters I find this time of year is Columbine Sawfly. And they are doing a number on the columbine in my yard! It is amazing how fast they can defoliate the plants.
This past week I found elongate hemlock scale on some stressed Canadian hemlock. This is an introduced pest that can be difficult to control. I’ve only seen it one other time in the past 12 years.
I also found some maple mite on Sun Valley and Red Sunset maple. This is the first time I’ve seen this pest this year.
I’m still seeming lots of aphids feeding on the new growth of a variety of plants. I also had to stop sale some blue rug junipers due to lack of watering.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
During the past week I have seen several locations with damage from ambrosia beetles. Most likely granulate ambrosia beetle (Xylosandrus crassiusculus). Look for tooth pick like frass tubes coming out of the trunks of infested trees. Frass tubes are easily broken off by wind and rain and in some cases you may only see sawdust. There are other species of ambrosia beetles that can cause similar damage. This pest becomes active as leaves start to expand in the spring. Infested trees can also develop multiple spots of gummosis on the trunks instead of frass tubes, but frass tubes are more common. Granulate ambrosia beetles begin to fly during leaf expansion and peak flight usually occurs in late April or early May. Adults are active throughout the grower season and a second smaller flight peak occurs in September. Most damage is seen in the spring, but damage can occur at any time of year. Granulate ambrosia beetle will infest nearly any deciduous trees. It has been reported to be an aggressive pest going after healthy host trees. However, most cases I have encountered in Indiana are occurring on hosts that are stressed. Some of the hosts I have observed infested with granulate ambrosia beetle include, red bud, Japanese snowbell, Japanese Weeping cherry, honey locust, mimosa, crabapple, tulip poplar, peach and dogwood. Healthy, uninfested trees adjacent to infested hosts should be protected with a residual insecticide. Infested trees can be left as a trap tree for a brief period and then destroyed once heavily infested. However, in most cases I recommend just destroying infested trees and protecting health trees with insecticide applications.
I still have not seen any woolly birch aphids. However aphids continue to be problematic on Spirea. Maple mites were found in Lawrence County last week. Look for stippling type damage and small, dark mites on the underside of leaves. I also found maple petiole borer causing damage to the new growth on red maples. This never seems to be a severe pest issue, but can cause some stunting of growth and I only occasionally see this pest in my region. Pine spittle bug was found on white pine in Lawrence County. Tulip tree scale was found in low numbers on saucer magnolia in Greene County, but I have not seen any large scale infestation so far this year. NO BAGWORM HATCH YET!
I has been fairly dry this spring so I have not seen a great deal of disease issues during my inspections. I saw the first symptoms of apple scab on crabapples in southern Lawrence County last week. Control of apple scab requires multiple, properly time fungicide applications on susceptible hosts. The best way to control scab is to utilize resistant cultivars. I also found what appeared to be a needlecast infection on Canaan fir. The inner needles on these trees were browning and dropping off. Closer inspection revealed black fruiting bodies on the under sides of the needles. Samples were sent to the Purdue Plant and Pest Diagnostic lab for confirmation. This is the first time I have seen this type of symptom on Abies (Fir).
Ren
Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
Last week I was inspecting dealers in Boone and Marion counties.
While at a dealer in Marion county, I found fruit trees infested with ambrosia beetles. These trees had paper labels wrapped around the base of the trunks, and when I lifted the paper wrappers, sawdust (frass) spilled out. Upon closer inspection I found frass “toothpicks” and exit holes on the trunks of many of these trees. Hosts included peach, cherry, and apple trees, and at least ¼ of all fruit trees we saw showed symptoms.
At a dealer in Boone county, I found butterfly bush with an uncharacteristic mottling pattern on the leaves. I suspected some type of virus and sent a sample off to the lab. The samples were negative for cucumber mosaic virus, tobacco mosaic virus, and potyvirus, and we are awaiting further testing.
At the same dealer, I also found a palm tree with a heavy infestation of scale insects.
Over the last week I’ve seen a lot of Aphids on Dipladenia and Hibiscus; Whiteflies on Squash and melons; Thrips on ‘Giant Crimson’ Mandevilla, ‘Julia Child’ Rose, ‘Kardinal’ Rose and ‘Grand Champion’ Red Rose; Two spotted spidermite on Mandevilla, and Botrytis Blight on Geraniums. I also saw virus symptoms on Mr. Lincoln Rose and included a couple of photos. Many virus infected plants will exhibit patterns of chlorotic wavy lines or mosaic patterns on the leaves. One positive find that I had this week was Green lacewing eggs on Dwarf Alberta Spruce. I’ve included a photo of that with a red circle around two of the eggs. I think I counted 6 total in the photo. Green lacewing eggs are white and are laid on a thin white stalk. Can you see the stalk that attaches the egg to the needle? This design actually helps against predators getting the eggs. Lacewings are considered beneficial insects because their larvae eat aphids, thrips, mealybugs, and other soft bodied insects that are considered pests.
First I need to print a retraction for the report I put out three weeks ago. I had indicated that I found Obscure scale on weeping cherry but as a coworker pointed out to me after the fact it looked to them like San Jose scale. My experience with San Jose is limited and the ones I have seen in the past have been much smaller than these. Never mind the fact that cherry isn’t a host for Obscure scale but it just goes to show you don’t jump to conclusions without thinking things all the way through.
Something I also saw two weeks ago was a couple of rust diseases on red cedar and I thought it would be good to show the symptoms which appear on the cedar end of the diseases instead of the apple, hawthorn, quince, sand erviceberry end which we are so used to seeing.
This past week I issued a number of stop sales for ambrosia beetles at a number of locations. The primary material that was being infected was sweet cherries, apples and peaches. I suspect the material was infected at the nursery of production and shipped into the state. I suspect it was infected prior to shipment because there was a wide range of host materials at each location but it was only the fruit trees mentioned that were infected and it was all from the same producer. One location I visited had a ninebark that was infected with fireblight and you could see where it had been spreading to other stock close by presumably through watering. I also found aphids on rhododendrons, sweet potato vine, penta, beards tongue and some others. I also found Gilardia smut on blanket flower and fletcher scale on hicks yew.
