Indiana Department of Natural Resources sent this bulletin at 07/10/2018 01:40 PM EDT
Weekly Review for July 10, 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.
High humidity means more leaf spots and mildews. I have been seeing quite a bit more black spot on roses and powdery mildew on an assortment of things over the last week.
Japanese beetle damage is quite heavy in places, but there are areas where the population is quite light as well. I hate to have to say this, but as a reminder, Japanese beetle traps only serve to lure more beetles to your property.
A first for me was finding a silver spotted skipper larva. While it’s widely distributed and fairly common, what makes this one unusual is finding the caterpillar outside a shelter that they usually build around themselves.
‘Tis the season of Japanese Beetle... I have noticed them on river
birch, roses, larch, Accolade elm, crabapples, and purple sand cherry. I also
saw Flea Beetles feeding on several varieties of weigela, hydrangea and
hollyhocks. Spider mites were found on butterfly bush, arborvitae, roses and
dwarf Alberta spruce.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
Japanese beetles are becoming a problem
at some locations in my region. During the least week I have seen them
feeding on Harry Lauder’s walking stick, Fine Line buckthorn, apples, purple
leaf plum and linden. Not a many new problems to report this week. The pest season is in full swing.
During the past week I found lace bug on
walnut trees in Vigo County. Look for stippling type damage and fecal
spots on the undersides of leaves. Nymphs and adults can often be seen on
the under sides of leaves if feeding activity is still occurring. There
are numerous species of lace bug. Some species are more host specific
while others tend to have a broad host range. On shade trees I frequently
encounter sycamore lace bug, birch lace bug and I have once had the opportunity
to see linden lace bug in Vanderburgh County. I also have encountered
Hawthorn lace bug which can infested many plants in the Roeseaceous
family. This pest cause damage to hawthorn, serviceberry, Pyracnatha
and sometimes Cotoneaster. Injury to shade trees is minor, but can
be of concern to clients. Severe infestation levels may stress trees, but
will not result in death of trees. Lace bugs on broad leaf evergreens can
be a more serious issue since they cause permanent injury to leaves that are
intended to be productive, healthy leaf tissue which are to remain on the plant
for multiple years. Hollies and boxwoods do not get invested with lace
bugs. However, Rhododendron, Azaleas and Pieris each have their
own species that can infest time. I frequently see lace bugs on Azaleas
in southern, Indiana but do not often see Rhododendron and Pieris
lace bugs. Recently I have been finding Chrysanthemum lace bug on asters
and golden rod species. Damage can be quite noticeable from this
pest. One lace bug I have not seen in the state is the fringe tree
lace bug. This pest has been found feeding on tree lilac in Nebraska.
There are numerous lace bug species that can be found in the
landscape. It is best to control these pest early on in the year
because multiple overlapping generations can occur which makes control
difficult.
During an inspection I found galls on a
hickory tree. There were two types of galls. One caused the veins
on the leaves to swell while the other gall was affecting the petioles of the
leaves. The gall infesting the petiole could possibly be the
hickory stem leaf gall aphid. According to Johnson and Lyon, there are 29
species of Phylloxera than can cause galls on hickories. Samples
have been sent to Purdue University for identification.
Fire blight is becoming a serious issue
for many susceptible plants. During the past week I found fire blight
infections in primarily apples. Look for the Shepard’s crook appearance
and tissue the turns black and rapidly dies. Prune out and destroy infected
material and make cuts 12 inches or more below the infected tissue. I
also am finding numerous leaf spots and found symptoms of Phyllosticta
leaf spot on paw paw. This is interesting because on paw paw, Phyllosticta
seems to coalesce into large necrotic areas while on other plants it cause a
small leaf spot. There is also a species of Phyllosticta that
causes tip blight on Arborvitae. My William Baffin rose in my back yard
has been infected with rose rosette disease which is a virus that is vector by
an Eriophyid mite called Phyllocoptes fructiphilus. The
plant has not yet died but is slowly declining as more and more of the new
growth is being replaced with infected growth. New healthy canes are no
longer being generated and flowering is being reduced. This disease can
infect any horticultural variety of roses and multiflora rose can often be a
reservoir for this disease. Look for new growth that is thick and
excessively thorny. Heavily infected plants should be destroyed. Keep it out of your garden.
I've gotten to see a couple of firsts in the last couple weeks.
I went on a diagnostic walk about in Cincinnati last week and was
able to view the work of the sunflower head clipping weevil. These weevils
girdle the stems of cone flowers and lay eggs in them. The girdling leaves the
head of the flower hanging by a thread which will eventually fall to the
ground. This process short circuits the plants natural defenses by cutting off
sap flow to the head and protecting the weevil larvae from the plants defense
compounds.
This same patch of cone flowers was also showing symptoms of mite
feeding on the flower heads as well as aster yellows disease.
I was also able to find some callery pear with hawthorn rust, I
just wish it was a little more severe. The infections I found were relatively
minor.
Another once in a blue moon find was the dusky birch sawfly on
some river birch.
One good thing I have noticed is that the bulk of the Japanese
beetle invasion has seemed to have subsided. They are still around but there numbers
seem to be significantly less or maybe I have just killed enough of them that
I'm not seeing as many. Either way they have done there damage.
I’ve included a couple of photos this
week. One is witch hazel cone gall, which is caused by an
aphid. The other is a Pseudocercospora sp. of fungus causing
a leaf spot on common lilac. The Pseudocercospora was confirmed by
PPDL through laboratory analysis.
Japanese beetle feeding continues to be an issue. I’ve even had
homeowners calling worrying about the massive defoliation taking place on
isolated landscape trees. While doing one inspection, virus symptoms were found
on bleeding hearts and columbine plants. Samples were collected and confirmed
for Tobacco Rattle Virus by Purdue’s Plant and Pest Diagnostic Lab. Tobacco
Rattle Virus can infect more than 400 different species and is caused primarily via
root nematodes, but can also be spread mechanically with pruning tools.
Hot weather makes it hard on the
beekeeper to get into hives.Heat stroke
is no fun.The bees can also be a little
bit feisty with the increase temperatures.Beekeepers have reported bees clustering on the outside of the
hives.The bees will do that when the
temperatures are so high.Adding another
honey super can give the bees more room to hang out.The beekeeper can also tip up the top cover
to help circulate the hot air out the top.The bees will collect water, sit at the front of the hive entrance and
move their wings. This action blows the water into the hive creating their own
kind of air-conditioning.
There have been some reports of swarming
the last two seeks.These may be late
due to the cold weather in April and the beekeeper not putting enough honey
supers on.Beekeepers still need to make
sure the queen has room to lay in the brood area. One way to do that is add
another honey super on.You could also
move open frames down into the brood area.Another idea is take some frames of honey, extract it, and put these frames
down in the brood area making them available for the queen to lay in.
Several beekeepers are reporting taking
off a good amount of honey already and have 4 to 7 honey supers still on
hives.We have to do the waiting game
now as the bees to cap over the honey in the cells.High humidity and high heat slows down the
capping process as it is harder to get the moisture in that honey to 18%.I do recommend that beekeepers try to get
their honey supers off by middle of August so they can start their varroa mite
treatments.Some of these treatments
take 6 weeks to complete.Completing the
treatment by the end of September will help insure that the bees hatching out
in late October into November (winter bees) will be mite free and healthy.
