Indiana Department of Natural Resources sent this bulletin at 05/09/2017 02:28 PM EDT
Weekly Review for May 9, 2017
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.
During an inspection this week in St. Joseph County, I found low levels of spruce spidermite on blue spruce and thrips and aphids on firs. I came across a few evergreens in very poor condition in an overgrown corner of the nursery. It took me a moment to realize they are Douglas fir with very heavy Swiss needle cast. This disease has hit Douglas firs so hard that you just don’t see very many in nurseries anymore. Some Eastern tent caterpillar was found on crabapples. They are getting toward the end of their larval stage in northern Indiana.
A perennial inspection in Kosciusko County turned up low levels of botrytis throughout the houses, probably due to keeping the houses buttoned up due to the low temperatures.
Finally, I had a fun homeowner call in St. Joseph County about evergreens planted along a property line. One by one, these arborvitae were disappearing starting by the river and working up the line. The branches were being removed from the site leaving only a chewed stump and some wood chips. Turns out, they were being visited by a beaver! I referred the gentleman to a District Biologist to develop a strategy to discourage this pesky critter.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
The rain has finally stopped! Of course you know during the month of August I will be complaining that we need rain. As a gardener I want 0.75 inches of rain per week and it should rain every 3rd day. Wouldn’t that be nice?
During the last week I found azalea lace bug in Vigo County at multiple locations despite the cold, wet weather. This is a bit early for this pest, but it can have multiple generations per year and early intervention is best to prevent multiple, overlapping generations. Damage appears as stippling that will coalesce and give infested leaves a whitish or faded appearance. Fecal spot, nymphs and adults can be found feeding on the undersides of leaves. Aphids were found on edible cherry and woolly birch aphid activity was also found. I am starting to see some low levels of leafhopper feeding activity on red maple and red bud, but I have not seen any hopper burn or leaf cupping on red maple. Look for small areas of stippling on leaves. Severe cases will stunt the growth of red maple. Maple mites have not been found yet. The heavy rainfall has been keep mites at bay so far this year. I found some damage from hawthorn leafminer. This is a blotch leafminer that cause small brown areas in mid spring. I have never seen severe damage from this pest and it seems to be just a minor nuisance early in the season. Rust and lace bug cause more significant and noticeable injury to hawthorns. Rose sawfly (Slug) populations appear to be subsiding over the last two weeks and I am noticing less new damage.
Photo 1 – Azalea Lace Bug Injury
Photo 2 – Aphids Causing Leaf Curl on Cherry
Photo 3 – Early Leafhopper Injury on Red Bud
Photo 4 – Hawthorn Leafminer Injury
The recent heavy rain is causing issues at many locations. Botrytis will likely became or has become an issue on many annuals and perennial plants. Ranunculus, primrose, gerbera daisy, geraniums and lavender seems to be particularly susceptible to this diseases. Increase air circulation around plants and dead head plants frequently to reduce the potential for infection. I have also seen some tip blight on Vinca minor. It typically starts as a leafspot that will progress towards the stem causing small branches to die. This is a common problem on this plant and can be caused by several fungi, including Phomopsis, Rhizoctonia and Phyllosticita. Damage appears similar and laboratory analysis is need to confirm the exact causal agent. Prune out infested stems and keep leaves raked out of plants to maintain good air flow in stand. In nursery setting, this is a problem that can result in plants that are not saleable. I have never seen it kill plantings in a landscape, but it can be a serious nuisance. Winter injury and canker were found on the tip growth of Japanese maples. This type of dieback could be caused by a number of different fungi. Infected areas should be removed to prevent potential spread to larger branches and shears should be disinfected between each cut.
Photo 5 – Early Stages of Tip Blight on Vinca minor
I don't have a lot to report this week. I've seen thrips and botrytis blight on geraniums, apple scab on Golden Delicious apple trees, and rose slug sawfly larvae feeding on Knockout roses.
The only thing of note from this week is the cynipid wasp larva that leads to oak apple gall got an early start this season and has caused some light leaf dropping to young leaves. Since this only affects leaves, treatment is nearly never warranted.
This past week, I also got to participate in STEM Night: Backyard Science at Pleasant View Elementary School in Zionsville along with chief apiary inspector Kathleen Prough and Division Director Megan Abraham. While some students learned about the anatomy of an insect while making pipe-cleaner butterflies, others spoke with our apiarist about different species of bees and the importance of pollinators and habitat. We also spoke with students about invasive plants.
I’ve continued to do dealer inspections during the last two weeks. The main issue I have found continues to be crown gall. To date this year I have found crown gall in a variety of things including crabapples, stone fruits, and willows with the largest amounts of infected stock being found in blueberries. I have also done a couple more Christmas tree growers and found a variety of conifer problems which included Swiss needle cast of Douglas fir, pine spittle bug on Scotch pine, and a pine rust on Scotch pine. As I was walking the field I had a couple of eastern black swallowtails flying ahead of me laying eggs as they went and managed to find one of the eggs as the female flew off. I also got lab results back for a couple of samples that I had sent in previously. I had Norway spruce and western white pine at another conifer growers which showed some a fair amount of damage due to needle cast which I couldn’t identify. The lab came back with Dothistroma needle blight on both.
Photo 8 – Swiss Needle Cast in Douglas Fir
Photo 9 -
Pine Spittle Bug on Scotch Pine
Photo 10 – Gall Rust on Scotch Pine
Photo 11 – The egg of an eastern Black Swallowtail
Photo 12, 13 – Dothistroma on white pine (left) and on Norway spruce (right).
