Indiana Department of Natural Resources sent this bulletin at 08/21/2018 08:51 AM EDT
Weekly Review for August 21, 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.
A nursery sent me a couple of photos from a homeowner that left me
curious.In the two weeks between seeing
the photos and making the site visit one of the trees went from heavy flagging
on the lower branches to completely dead.I was kind of stunned when I pulled up.My best guess is that something stressed the first tree leading to an
infestation of Zimmerman pine moth.Since then, the pine bark beetles have cleaned up that tree and moved on
to the others in the row.Interestingly,
Zimmerman only appeared to be present on the one tree.There are a high number of older red and
white pines across the property making removal of these trees a high
priority.
I inspected nurseries in Allen County this past week.Japanese beetles are still present, but the
numbers I saw were way down from previous weeks.I found them feeding on pin oak, Whitespire
birch and weeping willow.Fall webworm
is becoming much more abundant.I found
them feeding on sweetgum and several redbud trees.Other insects and diseases I found were lace
bugs on bur oak; anthracnose on London plane tree; apple scab on crabapple;
European red mite on serviceberry and ‘Winter King’ hawthorn; white pine weevil
on white pine and Norway spruce; flat headed apple tree Borer damage on sugar
maple; maple mite on red maple; needlecast on Blue spruce and Zimmerman moth on
Austrian pine.
A few of us had the opportunity to attend a training session on
bur oak blight (BOB) last week in Crown Point.BOB is a disease caused by the native fungus Tubakia iowensis that mainly affects bur oak but can on occasion
infect swamp white oak.It requires
abundant rain in April and May to infect trees and the spores are dispersed by
water droplets.It goes into a latent
period after initial infection and symptoms don’t begin to appear until July.
BOB is slow to develop and takes several years to spread throughout the crown
with symptom progression going from the bottom up and inside out.Early symptoms in July include black necrotic
veins on the underside of the leaves.In
August, these expand into wedge shaped brown lesions on the upper leaf surface
along with black fruiting bodies along the veins on the underside of the
leaves.The infection can spread to the
petioles where it will cause the infected leaves to turn completely brown.Infected petioles become swollen at the base
and remain attached to the tree.These
petioles are the source of infection in subsequent years.Bur oak trees with larger acorns seem to be
resistant, however smaller acorn trees that are stressed from other problems
such as two-lined chestnut borer can be killed so maintaining tree vigor is
important.Fungicide treatments using
Propiconizole (Alamo) can be used on trees with moderate to severe infections,
but it’s important to make the application in May to early June before the
current years symptoms appear.It’s also
important to treat trees prior to infestation by two-lined chestnut borer.Healthy trees should not be treated.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
Well, we are certainly getting enough rain in my region.I have not been doing many nursery inspection
during the last week because I have been working on kudzu eradication during
the last two weeks. Yes, kudzu exists in Indiana and has been found in the
counties bordering Michigan and there was even a confirmation of kudzu in
Ontario, Canada in 2009.The cold
weather will not kill kudzu, but merely slow it down.During the last 13 years we have treated 125
sites in the state.I have included a
picture of a kudzu site in Greene County.This is a large 5 acre site that is proving to be quite a challenge to
control.Looking at a kudzu patch truly
makes one appreciate and understand of the threat invasive species can cause to
our environment.
Last week I was contacted by one of my growers that was a having
an issue with mites on orchids.I have
inspected this location for 16 years and have never observed mites on the
orchids in the greenhouse.I have heard
of broad mites and cyclamen mites infesting orchids and occasionally
two-spotted spider mites (Tetranychus
urticae), but most of the orchid collections I have worked with never had
serious mite issues because frequent overhead watering washes them off of
plants.When I arrived at the greenhouse
I was amazed I what I had observed.There were so many shed skins that the undersides of the leaves appeared
white.Mites were causing pitting,
sunken areas and necrosis.It was not
the stippling type damage you would expect to see with Tetranychid mites.There was not any webbing and the mites, were
red and very small.They were too small
to be Tetranychus cinnabarinus
(Carmine Spider Mite). I believe they may be Phalaenopisis mites (Tenuipalpus pacificus) or possible
Omnivorous mites (Brevipalpus
californicus).Both of these mites
are in the family Tenuipalpidae, the false spider mites and do not produce
webbing.The hosts included Phalaenopsis and Paphiopedlum.We inspected
numerous plants and believe that mites may have been introduced into the
greenhouse from a shipment of plants that was received from an out of state
source.I have included some interesting
pictures here for your viewing pleasure.
Ren
Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
A few days ago I found this hornworm on my tomato plant, covered
in pupae of a parasitic wasp. I was hoping to observe what happened over the
next few days but unfortunately the hornworm disappeared during the heavy rain
we had last week.
Last week I did an inspection at a small nursery with two greenhouses.
They were having some problems with whiteflies. On this tomato plant, you can
see the adult whiteflies. I also saw a lot of larvae on many plants, including
the leaves of this strawberry plant.
I noticed some 'Zebrina' mallow that had ants busily crawling up
and down the stems and sure enough they led me to an aphid infestation on the
leaves.
Another interesting thing I saw was this raspberry plant that had
unusual bumps all over the old stems. I was able to peel them off and they were
brittle and papery and full of a sawdust-like substance. I suspected it was
some type of scale insect but found no evidence of crawlers or live adult
insects. I sent a sample to Dr. Cliff Sadof at Purdue who is an expert on scale
insects, and he identified them as European fruit Lecanium scale.
Lastly, in the second
greenhouse, this nursery was having a problem with caterpillar feeding, and I
found several different caterpillar species including this white-marked tussock
moth.
The other
week I did an inspection where I might have stumbled on something new. One
grower I visited was having problems with various size London Plane trees. Some
of the stock was new and transplanted this spring other material was more
established being put in last year. Almost all of the plants showed stem
dieback with what appeared to be cankers. Below the dieback/canker the tree
would be suckering badly. I took a couple of samples and sent it off to PPDL
but tentatively I think it may be Canker Stain of Sycamore/Plane tree.
While doing
survey for spotted lantern fly I found an interesting insect, the Ailanthus web
worm. This location of Ailanthus was quiet heavily infested with the web worms
but didn’t appear to be causing any great harm to the trees.
Just
a few feet from my ailanthus patch I noticed a large patch of cup plant.
However, I almost misted them because there was very little bloom which struck
me as odd. Upon further investigation I found a very high population of
sunflower head clipping weevils. Almost every flower that was still intact had
multiple weevils sitting on it.
