Indiana Department of Natural Resources sent this bulletin at 06/26/2018 01:40 PM EDT
Weekly Review for June 26, 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.
So, last week was National
Pollinator Week. Yup, we forgot to
write about it. However, it’s never too
late to do something to improve habitats for these important insects, birds,
and mammals. For more information visit pollinator.org or
Purdue’s Gardening with
Pollinators page. If you are
interested in planting a larger area along a stream or Indiana highway, the DNR
has the CORRIDORS program in cooperation with INDOT, NRCS, Pheasants Forever,
and Quail Forever. For more information,
visit the Indiana CORRIDORS
Program page.
I conducted inspections in Cass and Fulton Counties. Japanese beetles are out in full force with
elms taking some pretty serious defoliation. Also saw the start of apple scab on Prairefire crabapples. I saw balsam twig aphid damage on firs,
rhizosphaera needlecast on blue spruce and a considerable amount of nutrient
issues on larger plants, specifically rhododendron.
Photo 1 – Japanese beetle damage on Princeton Elm
Photo 2 – Typical lower branch dieback on blue spruce from
rhizosphaera needlecase
Photo 3 – Balsam twig aphid damage on fir
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
Japanese beetles had emerged in large numbers during the week of June 13, 2018, in Greene County. I have not
observed a great deal of damage in my region yet. I am continuing to find two
spotted spider mite infestations on many plants including Lobelia, Sorbaria,
butterfly bush, burning bush and Brugmansia. Bagworm and white pine weevil are
giving many evergreen growers a headache.
During an inspection, I found a severe case of white prunicola
scale on Japanese weeping cherry. The
scale is white in color and looks similar to white peach scale. Low level populations never cause serious
damage. However, in the cause I found last week there were multiple trees in
which the scale completely encrusted and circled the branches and was causing
branch dieback on the tree.
I am starting to see red headed flea beetle feeding damage and
adults on Weigela and Hydrangea paniculata. This pest is an increasing problem in the nursery industry and leaf
feeding activity can cause damage that reduces the sale value of plants. Look for holes and defoliation that occurs
towards the center of the leaves. Adults that are black, with a slightly reddish head can be found on the
undersides of leaves. However, they can be
difficult to find since they often hop and fly away when disturbed. Some nurseries are treating for this pest
because the experience enough injury that sales are affected by the presence of
the damage.
Hibiscus sawfly was found on perennial hibiscus in Putnam
County. Look for chewing damage and
small larvae feeding on the undersides of leaves. Remember, these are sawfly larvae and Bt will
not work to kill them. You must use and
insecticide labeled for sawflies. I do
not often see this pest in my region. Another interesting pest I found this week was Eriophyid mite galls on
low gro sumac. The galls were very
small, similar to those seen on silver maple resulting from maple bladder gall
mite. There was not any leaf drop or
leaf yellowing caused by the infestations I had found during inspection. I am also starting to see new damage from
boxwood leafminer on boxwoods. Boxwood
leafminer adults emerge during leaf expansion and lay eggs in leaf tissue. As larva develop, they will continue to cause
a blotch mine, but most of the damage will not be seen until next spring as
larva mature and begin to feed more aggressively. Treat now to prevent more significant injury
which can occur in late winter and spring of next year.
Photo 4 - Red Headed Flea Beetle and Foliar Feeding Injury
Photo 5 - White Prunicola Scale on Japanese Weeping Cherry
Photo 6 - Close up of White Purnicola Scale
Photo 7 - Sawfly on Perennial Hibiscus
Photo 8 - Boxwood Leafminer inside leaf tissue
Well it has been an interesting week for diseases. During an inspection, I found significant
dieback and black leaves hanging on the bottom of Coreopsis grandiflora ‘Golden
Sphere’. I sent samples to the Purdue
Plant and Pest Diagnostic lab to find out what was going on with the plants. The sample was positive for downy mildew,
(Plasmopara sp). Apparently this
pathogen exists in the United States, but it is the first time it has been
reported on Coreopsis grandiflora. The grower provided additional samples on C.
grandiflora ‘Presto’ and they were also positive for downy mildew. The exact species of downy mildew has not
yet been determined, but pathologists are working to see if they can determine
it.
Hosta Virus X was confirmed on Paul’s Glory Hosta. Look for
mottling, leaf cupping or strap like leaves on cultivars that do not ordinarily
have those types of leaves. Laboratory
testing is necessary to confirm the presence of these diseases. If you look at the picture I have below,
there is an unknown cultivar of Hosta grown from seed that has viral
symptoms. It has tested negative for
Hosta Virus X, Impatiens Necrotic Spot Virus, Tobacco Mosaic Virus and Tomato
Spotted Wilt Virus. There is some
additional testing being conducted to determine which virus may be infecting
the plants. It is nearly impossible to
properly field diagnosis exactly which virus may be infecting a plant.
Needle cast diseases continue to be a problem on many evergreen
plants. Last week I found Rhizosphaera
needle cast on blue spruce. I also found
symptoms of Swiss needle cast on Douglas fir and an unknown needle cast on red
pine. It is important to know exactly
which needle cast is present because the timing of effective fungicide
application will be dependent on the type of needle cast you are trying to control. Maintain good air circulations around trees
by keeping nurseries mowed and culling overgrown or unsaleable trees. Also, do
not plant evergreens in fields that have poor drainage conditions.
Nutrient deficiencies
continue to be a problem on many plants. Nutrient problems have been seen on dogwoods, roses, Jacob’s ladder,
Itea, Fothergilla and witch hazel during the last week. As the weather warms we rely more on
irrigation. It is a good idea to know the
quality of your water. Get your water
source tested, especially the pH. The pH of my water coming out of my tap is
8.6. Most of my evergreens are not
happy when I start watering regularly with high pH water. This can also change the chemistry in your
root zone and induce nutrient deficiencies that would not otherwise be there if
it were raining frequently. There are
some growers that treat water before they use it for irrigation and it can save
a lot of issues, especially for container grown plants.
Photo 9 - Symptoms of Downy Mildew on Coreopsis grandiflora ‘Presto’
Photo 10 - Confirmed Hosta Virus X on cultivar Paul’s Glory
Photo 11 - Virus symptoms but has tested negative for multiple
Viruses
Photo 12 - Needle Cast Symptoms on Red Pine, ID Pending
Photo 13 - Severe
Iron Chlorosis on Dogwood
Ren
Hall (Nursery Inspector & Compliance Officer)- RHall@dnr.IN.gov
Two weeks ago, I helped out at a group inspection in Jackson
County and saw these bagworm larvae feeding on hemlock.
Photo 14 - Bagworm larvae on hemlock
Last week I did inspections in Boone County. At one nursery
dealer, I found unusual mottling on delphinium leaves and sent a sample to the
lab for testing and am awaiting the results.
Photo 15 - Possible
virus on delphinium
The Japanese beetles were out when I inspected a Christmas tree
grower in my territory, and I spotted the adult beetles on Canaan fir, Douglas
fir, and white pine.
Photo 16 - Japanese beetle on fir tree
There were almost no insect or fungal problems at this grower, and
the place was immaculately mowed which made inspecting this place very nice.
The only other problem we noted was an occasional tree that had mechanical
damage caused by the mower or trimmer nicking the trunk, like the white pine in
this picture.
I can’t say that I found to much that was interesting this week
(aside from what will be included in next week’s post).
I found some leaf miners on buckeyes, apple scab is starting to
increase in severity, and Petiole gall on hackberry. I also found a few non-pest species worth mentioning.
Photo 18 - Dogbane Leaf Beetle
Dogbane leaf beetles are pretty stunning if you ever get the
chance to examine one up close. They feed on dogbane which is in the milkweed
family and benefit from them in the same way as Monarchs. The bright coloration
serves as a warning to wood be predators of their toxicity. They have “aposematic coloration,” a term that I just learned today from Joe Boggs over at OSU.
Photo 19 - Petiole Gall on Hackberry
Petiole Gall on Hackberry isn’t something I see a lot of but one
nursery consistently has this in quite high numbers. Although found in high
numbers I don’t see much in the way of long-term negative effects for the
trees.
Photo 20 - Gumosis on “Weeping Pink Snow Showers Cherry”
Japanese Beetle are really starting to kick into high gear. Last
week I had noticed an overabundance of Japanese beetles on my buckwheat cover
crop that is in my garden and chicken
run, while there were relatively few on my sweet cherry, willows and apples. I
had my hopes up that they would prefer the buckwheat to my fruit trees but
within the last week they have found their way back to the trees. I'll confess
that my real hope was the beetles would be attracted to the buckwheat in the
chicken run. I watched a couple dozen unsuspecting beetles as they would buzz
along three feet off the ground through the buckwheat blossoms only to have a
chicken leap up and snatch it from midair. It was a bit like watching a micro aerial version of Jaws. Buckwheat
might not work but I’ve noticed another one of my cover cropped garden beds
that the beetles are decimating the sunhemp, so I already have a plan in the
works for next year. I’m bound and
determined to make death by chicken a viable control option for Japanese
beetle.
Photo 21 - Japanese Beetle on buckwheat flower
Photo 22 - Chickens waiting for an unsuspecting Japanese beetle
The most notable find of the week was Japanese maple scale. These
little guys can really be hard to find especially in low numbers. Rough bark or
bark with a light color only makes it harder to spot them. They look a little
bit like oyster shell scale but about half to a third the size. The trouble
with them is they don’t have a real well-defined crawler period so it can be
difficult to figure out a timely window for application of control measures to
be applied. I found these guys at two separate nurseries this week near
Indianapolis. Mainly on red maple but also on zelkova and elms. One nursery had
beat me to the punch and had already treated for them. By the looks of it, the
application had worked because when I did my smear test (rub the scale off with
my thumb) there was no liquid (bug guts) was produced. I tried to capture this
very technical process with pictures but the optics on my I-phone weren’t up to
the task. In all seriousness it's simple but useful.
Photo 23 - Japanese Maple Scale on Zelkova
According to the local weather station, we are just past peak
activity for the first generation of these guys around Indy. There will be a
second generation later on this year. For a more detailed treatment of Japanese
maple scale, see the University of Maryland Extension bulletin Japanese Maple Scale
– A Pest of Nursery and Landscape Trees and Shrubs.
For tracking growing degree days, I use USPest.org.
Photo 24 - Another individual who benefits from “aposematic
coloration”. Monarch on swamp milkweed in my yard.
