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8/22/2019 Kentucky Pest News, August 6, 2013
1/8
Online at:www.uky.edu/KPN
Number 1351 August 6, 2013
WATCH FOR
Brown Marmorated Gaining Momentum
CORNDetection of Southern Rust in Kentucky Corn
GRAIN CROPSKudzu Bug Moves Into Central and Western
Tennessee
SOYBEAN
Frogeye Leaf Spot at Epidemic Levels in SomeFields
FRUIT
Spotted Wing Drosophila Update
ORNAMENTALSDaylily Leaf Miner
HOUSEHOLDWood Cockroach
DIAGNOSTIC LAB HIGHLIGHTS
INSECT TRAP COUNTS
WATCH FOR
Brown Marmorated Gaining MomentumRic Bessin, Extension Entomologist
Brown marmorated stink bug (BMSB) is getting
more common in some backyard gardens and onsome vegetable farms in central and eastern
Kentucky. Although it has been recorded in 27counties in Kentucky, it has only been in a few
long enough to be more than just a curiosity orminor nuisance. In fact, while sampling for SWD Icame across several BMSB on blackberries.BMSB has a tremendous host range whichincludes many ornamental plants, some
vegetables, most fruit crops, and some row crops.
Figure 1. BMSB nymph on blackberries.
It tends to feed on the thick succulent parts of
plants which is often the fruiting structure. Wealso need to manage both the native green stink
bug and the brown stink bug complex on thesesame crops.
With the BMSB still at relatively low levels,controls used for other stink bugs should provide
sufficient control. Currently we are evaluatingselective screening to exclude BMSB from high
value organic crops. Preliminary results indicatethat screening material of less than 1/6 inch willexclude BMSB adults. Some other states arestudying the effectiveness of trap cropping andfarmscape management of BMSB.
Look for BMSB insecticide recommendationslisted in our future spray guides.
CORN
Detection of Southern Rust in Kentucky CornPaul Vincelli, Extension Plant Pathologist
Southern rust was confirmed in the past week oncorn in Caldwell County. Based on photos froman industry representative, it also appears to be
present in Logan County (lab confirmation
Lexington, KY 40546
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pending). The disease has been developing insouthern Georgia and Mississippi throughout July,
and it also has been detected recently in Nebraska,Arkansas, Kansas, and Illinois. Based on these
observations, I suspect that southern rust is presentat low levels in several locations in Kentucky,
although scouting thus far suggests it is not yetwidely prevalent. In other words, there is no needfor panic, just watchful eyes.
Two rust diseases in cornTwo rust diseases may be found on corn in
Kentucky: Common rust (Figure 2) and southernrust (Figure 3). Common rust is very common,
being found at low levels in many fields in mostyears, including this year. Adequate levels of
resistance to common rust are found in the largemajority of hybrids adapted to Kentucky. In
contrast, southern rust is much more sporadic inKentucky, and very often comes in too late tocause damage. However, if it shows up early
enough, it is capable of causing significant cropdamage.
Common Rust
Pustule color is brick-red to cinnamon-brown Pustule shape is circular to elongated. (In
some corn germplasms, infections sites of
common rust can mimic gray leaf spotrectangular spots limited by veinsbut the
pustule will be evident if you look with a handlens.)
Pustules erupt through both upper and lowerleaf surfaces.
Pustules are found only on leaves Develops in cool to mild weather (favored by
temperatures of 59-77F when leaf surfacesare moist)
Figure 2. Close-up of common rust of corn. (Photo: Alison
Robertson, Iowa State University)
Southern Rust
Pustule color is reddish-orange Pustules are small, generally circular. Pustules are densely crowded on the upper leaf
surface.
Pustules can occur on leaves and husks. Develops in very warm, humid weather
(favored by temperatures of 70-85F whenleaf surfaces are moist).
Figure 3. Typical pustules of southern rust of corn. (Photo:
Paul Vincelli, University of Kentucky)
Disease threat posed by southern rust
Southern rust is always a concern whenever itappears in Kentucky this early. The reasons forthis are:
Many corn hybrids adapted to Kentuckyconditions are susceptible It can be a very fast-moving disease.Disease activity proceeds rapidly under warm, wetconditions. Infection of leaves is optimal whenleaf surfaces are wet with temperatures of 70-
85C. Cool nights help to slow disease progress.
Southern rust poses the greatest risk to late-plantedcrops, and we have many of those this year. I
definitely suggest scouting for this disease in late-
plant crops.
We dont have well-researched spray guidelinesfor southern rust. However, here are some
thoughts that may help with spray decisions:
Detection of a few infected leaves does notmean that the field must be sprayed. Howmuch damage the disease causes depends on
how fast disease progress occurs, which ishighly weather-dependent. Kentucky
8/22/2019 Kentucky Pest News, August 6, 2013
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conditions can sometimes be favorable forrapid disease progress, but not always. If we
get into a pattern of dry weather with coolnights, disease progress can slow down
substantially.
Under highly disease-favorable weather(which doesnt always occur in Kentucky):o The disease can go from undetected in the
field to substantial damage in 5-6 weeks.o If the disease is present more or less
throughout the field (even at very lowlevels) in all levels of the canopy (lower,middle, and upper), it can cause
substantial damage in 2-3 weeks.
Thus, detection of the disease in crops in thekernel milk stage (R3) or earlier suggests a
significant risk to yield and stalk health, if weather
permits continued rapid disease development.Detection in later crop stages is where decisions
get more difficult. The onset of the kernel doughstage (R4) is still roughly 4-5 weeks from
maturity; and the onset of the kernel dent stage(R5) is roughly 3-4 weeks away from maturity.That is enough time for crop damage to occur, but
only if the disease is established throughout thefield and conditions are highly favorable for
disease progress. Southern rust activity late ingrain-fill can take the form of yield loss or, morecommonly, widespread stalk rot. Rapid loss of
green leaf area can cause the corn plant tocannibalize the stalks in order to finish fillingthe grain, resulting in weak stalks. This can becompounded by infection by common stalk rotfungi, and in worst-case outbreaks, the entire field
may be flat before harvest.
In considering whether a fungicide application isjustified, consider the following:
Has southern rust been detected in the area? Itmay not even be present. A few days ago, I
did a quick tour through a western Kentucky
county and found no southern rust, so it is notyet a widespread threat.
If the disease is present, is it a field with highyield potential? What is the weather forecast?
How widely established is the disease? Isit on just a few leaves, or throughout the field?
Effectiveness ratings for various commercialfungicides against southern rust are available
athttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.
A comment on health risk: A badly infected fieldis producing many billions of rust spores.Although these spores are not a recognized health
hazard, breathing mold spores in general mayinduce respiratory problems in some individuals,especially if exposed repeatedly. If you
experience or have a history of such reactions, useof a properly-fitted dust respirator may be
advisable if you are among heavily rusted plants,including during combining. Combine filters may
filter out some mold spores but efficacy variesdepending on the condition of the cab, seals, and
filter system.
Acknowledgements
Thanks to Bill Dolezal (Pioneer Hi-Bred), MarkA. Purschwitz (UK Biosystems and AgriculturalEngineering), and Don Hershman (UK PlantPathology) for reviewing a previous draft of thisarticle.
GRAIN CROPS
Kudzu Bug Moves Into Central and WesternTennesseeDoug Johnson, Extension Entomologist
Kudzu bug continues to be found ever closer toKentucky (KY). Until just recently, Kudzu bug in
Tennessee (TN) was found only in the easternportion of the state where few soybeans are grown.These infested counties are the closest to KY, butin an area of KY where few soybeans occur.Unfortunately, within the last week, this pest has
been found in two additional TN counties. Both of
these TN counties are soybean producing areas ofcentral and west TN (See the map, Figure 4).
http://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdf8/22/2019 Kentucky Pest News, August 6, 2013
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Figure 4. Kudzu bug distribution
Though these two finds are no closer to the KYborder (in fact not as close) as the eastern TN
infested areas, they are much closer to the KYmain soybean production area. Shelby County is
the greater Memphis area and on the US-51 routethat leads directly into the KY Purchase area.Lincoln County is on the TN-Alabama line just
east of I-65 and astride US-231 that leads directlyinto middle TN.
Certainly, these finds do not indicate anyimmediate problem for Kentucky. Nevertheless,
we continue to see movement of the populationtoward KY and now toward our main soybean
production area; as expected, along major trafficroutes.
No immediate action needs be taken save keepingan eye out for the presence of these insects. If you
find what appears to be a Kudzu bug or a brownmarmorated stink bug, please get them to yourlocal County Extension office so that they can be
properly identified.
Note: I have started a twitter feed specificallyaimed at information on invasive stink bugs asthey relate to KY grain crops. If you would like to
receive this twitter feed you may go to your twitter
account and follow @DrDougStinkBugs or searchon my email [email protected]. Thisfeed will be used only for information/updates on
invasive stink bugs in grain crops (currentlyKudzu bug and brown marmorated stink bug); soyou will not be overwhelmed with unwanted
tweets. The major outlet for more detailedinformation on these pests will remain the Grain
Crops Update blog(http://graincrops.blogspot.com/ )
and Kentucky Pest News newsletter(http://www2.ca.uky.edu/agcollege/plantpathology
/extension/kpnindex.htm)
For All things Kudzu bug, see: the KudzuBugWebsite athttp://kudzubug.org/
SOYBEAN
Frogeye Leaf Spot at Epidemic Levels in Some
FieldsDon Hershman, Extension Plant Pathologist
Frogeye leaf spot (Figure 5) caused by the fungus,
Cercospora sojina, is at epidemic levels in somesoybean fields east of I-65, and especially in
northeast KY. The main question being asked is,Should I spray a fungicide? The answer dependson the extent of the disease and the average stage
of the plants. If the crop is before, at, or near stageR5 (i.e., pods full size, but beans are very small),
then spraying may be advisable as long as thedisease is established throughout the field inquestion and the crop has good yield potential.
However, the closer fields get to the R6 growthstage (pods filled), the less likely spraying will beof any benefit. If the disease is not alreadyestablished in a field, there is a good chance it willonly be a minor player, perhaps because the
variety has some resistance. There are manyavailable varieties that are resistant to frogeye leafspot. Growers with problems this season, shouldseek out and plant frogeye-resistant varieties in
problem fields the next time they grow soybeans.
Figure 5. Foliar symptoms frogeye leaf spot.
mailto:[email protected]:[email protected]:[email protected]://graincrops.blogspot.com/http://graincrops.blogspot.com/http://graincrops.blogspot.com/http://www2.ca.uky.edu/agcollege/plantpathology/extension/kpnindex.htmhttp://www2.ca.uky.edu/agcollege/plantpathology/extension/kpnindex.htmhttp://www2.ca.uky.edu/agcollege/plantpathology/extension/kpnindex.htmhttp://www2.ca.uky.edu/agcollege/plantpathology/extension/kpnindex.htmhttp://kudzubug.org/http://kudzubug.org/http://kudzubug.org/http://4.bp.blogspot.com/-LIuuHXQCwPs/Ufq0R4Y3AMI/AAAAAAAAAEg/Etx3rKAQkKo/s1600/2+Frogeye+Lewiis+County+2013.jpghttp://kudzubug.org/http://www2.ca.uky.edu/agcollege/plantpathology/extension/kpnindex.htmhttp://www2.ca.uky.edu/agcollege/plantpathology/extension/kpnindex.htmhttp://graincrops.blogspot.com/mailto:[email protected]8/22/2019 Kentucky Pest News, August 6, 2013
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In the meantime, spraying a fungicide is the onlyavailable option if frogeye is a problem now. If
you have a field that meets the above criteria, it isimportant to spray as soon as possible. Be aware,
however, that fields showing significant diseasenow will not yield to their fullest potential.
However, if the crop still needs 3-4 weeks for thepods to fill, it may be possible to limit lossescompared to where the disease is left to develop
unchecked. Many doublecrop soybean fields inthe state are just now entering the early pod stages.If frogeye is a risk in these fields, the best targetapplication timing is the R3 growth stage (pods3/16-inch-long in upper four nodes). Under heavy
disease pressure, a follow-up spray at the R5 stagemay be necessary to achieve maximum disease
control.
As a result of research funded by the KY SoybeanPromotion Board during 2011-12, we know thatabout half of the frogeye fungus populations in
KY are resistant to strobilurin fungicides. Sincemost farmers cannot know if they have strobilurin-resistant or -sensitive strains, they must assume the
strain of the fungus in their fields is resistant tostrobilurins. Thus, if you decide to spray a crop for
frogeye leaf spot control, it would be best to useone of the available triazole fungicide products ora combination pre-mix fungicide that includes a
triazole and a strobilurin. The main goal is to
avoid applying a solo strobilurin product (e.g.,Aftershock, Aproach, Evito, Headline,Quadris) since these products will have reducedefficacy if a strobilurin-resistant strain ofC. sojina
is present. Contact your local county Extensionoffice, or fungicide salesperson, for help in
selecting the best available triazole orstrobilurin/triazole premix for control of frogeyeleaf spot. You may also want to view a current
fungicide use efficacy table for soybean on the UKGrain Crops Extension Web
site:http://www.uky.edu/Ag/GrainCrops/Briefs/C
DWGCornFungicideEfficacy_Table_2013_FINAL.pdf
FRUIT
Spotted Wing Drosophila UpdateRic Bessin, Extension Entomologist
Based on apple cider vinegar trap catches traps,
emails and phone calls, spotted wing drosophilaactivity is continuing to increase. Activity appears
to be state wide with all of our current trappingsites positive for SWD and numerous reports ofSWD larvae in fruit or damage to fruit. The
reported damage is described as rotting, mushyfruit with small pencil-lead sized holes.
Damaged crops in Kentucky include blackberries,blueberries, and peaches from both commercial
and backyard plantings.
Figure 6. Spotted wing drosophila larvae on blackberries.
We have two factsheets that describe the pest andwhat commercial producers can do to help reduce
losses. Homeowners do not have the samechemical controls available, but they do havesome. For both commercial and backyard
producers, it is critical to alternate between modesof action with this pest as it has a very short
generation time, about a week. It is also importantto read the labels carefully and obey pre-harvest
intervals, the time between the final spray andwhen the crops can be picked. The pre-harvestinterval allows for weathering of the residues bysunlight, rain, and other factors to reduce levels toacceptable levels. SWD females are reported to
hide in the densest part of the canopy, so higherpressure will result in better coverage and control.
http://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdfhttp://www.uky.edu/Ag/GrainCrops/Briefs/CDWGCornFungicideEfficacy_Table_2013_FINAL.pdf8/22/2019 Kentucky Pest News, August 6, 2013
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Figure 7. SWD egg laid under the skin of blackberry with
breathing tubes protruding.
Homeowners wanting to spray to reduce lossesneed to read and follow label directions carefully.
Available products include malathion and CaptainJacks Dead Bug Brew, but home garden and
commercial formulations of malathion varyconsiderably both in terms of the crops uses andthe days to harvest. Clean harvesting and
disposing of damaged berries is also encouraged.Burial of fruit has not been effective as the adults
can emerge from relatively deep burial, butplacing damaged berries in clear plastic bags andleaving those sealed bags in the sun has been
effective.
Larval SamplingWith the recent arrival of this pest, it may be
helpful to periodically check fruit for the presenceof SWD larvae. To do this, select only fruit thatotherwise appear sound and healthy. This methodrelies on floating the larvae in sugar water or saltwater solutions to separate them from crushed
berries. To mix the solution, add either cup
sugar or cup salt into 1 quart of warm water andstir until dissolved. Place a dozen or soundamaged berries into a gallon sealable bag.Lightly squish the fruit in the bag then add the
sugar/water or salt/water solution. Agitate the bagto separate the larvae from the fruit pulp, then let
the contents settle. The larvae should float on thesurface of the solution and appear as white larvaethat are pointed on one end and more blunt on the
other.
Figure 8. Numerous SWD larvae floating on a sugar water
solution after being dislodged from blackberries.
ORNAMENTALS
Daylily leafminerLee Townsend, Extension Entomologist
The daylily leafminer is a relatively new pest
(2006) that has been detected in severalsoutheastern states. The small yellow maggots
feed in the leaves ofHemerocallis species andtheir cultivars, leaving obvious silver tunnels.
Figure 9.
Daylily
leafminer
tunnel in
Fayette
County
Hemerocallis.
Reddish object
at the end of
the tunnel is a
pupa.
The leafminer does not appear to kill plants butthere is a obvious cosmetic impact. There areseveral generations each year and activity can
persist until leaves senesce.
The adult, which resembles a very small house fly,can be seen resting on daylily blooms.
No specific chemical controls have beendeveloped but contact insecticides applied to the
foliage generally will not penetrate the plant to killthe larva. Removing and destroying infested
leaves may reduce populations somewhat.
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HOUSEHOLD
Wood cockroachLee Townsend, Extension Entomologist
Wood cockroaches live under loose bark, incavities of fallen or dying trees, or in stumps. They
are natives of moist woodland habitats where theyfeed on decaying organic matter.
Figure 10. Wood cockroach
These cockroaches are accidental invaders in
homes and buildings in and around wooded areas.They are especially active during their summermating season. Winged males can fly shortdistances; lights can draw large numbers of themto homes and structures. They can get inside a
number of ways- by crawling under exterior doorgaps, through open windows, gaps around pipe orelectrical service, or through cracks and crevices.
While it looks like a typical cockroach, the
wood cockroach has a pale, light white ortransparent stripe on the outer edge on the thorax.It behaves differently from the house-infestingspecies. Wood cockroaches are not secretive; theyare active day and at night and usually dont run
when approached. They will wander about thehouse without congregating in any particularlocation, like a kitchen or bathroom. They are anannoyance but wood cockroaches dont becomeestablished indoor pests because the air is too dry
for them to survive for long.
While there can be many of them; they are atemporary problem so there is no need for
extensive use of insecticides in the home.Cockroaches found indoors can be swatted anddiscarded or sprayed with in aerosol insecticide
containing pyrethrins .
The following steps may be helpful if wood
cockroaches are a chronic problem
Wood cockroaches prefer quiet, undisturbed
moist areas such as heavily mulched or naturalized
areas or stacked firewood. Reducing clutter andincreasing light and air penetration makes these
places less attractive for the insect.
Install tight-fitting window screens and doorsweeps to exclude wandering cockroaches and
other insects. Sticky card mouse/insect traps canbe placed in these areas to trap wanderingcockroaches near entry doors.
Males are attracted to lights at night, limitinglight use, especially around exterior doors, might
be of some benefit.
In severe cases, insecticides can be applied as a"barrier treatment" around the base of the
foundation. Pay particular attention to doorthresholds, garage and crawl space entrances,
including foundation vents. Examples includecarbaryl (Sevin), or any of the pyrethroidinsecticides: bifenthrin (Ortho Home Defense
Perimeter and Indoor Insect Killer), cyfluthrin(Bayer Advanced Home Pest Control Indoor &Outdoor Insect Killer), or permethrin (Spectracide
Bug Stop).
DIAGNOSTIC LAB HIGHLIGHTS
Julie Beale and Brenda Kennedy, Plant Disease
Diagnosticians
Agronomic samples diagnosed in the PlantDisease Diagnostic Lab in the past week haveincluded gray leaf spot, Physoderma brown spotand southern rust on corn; brown stripe on
orchardgrass; brown spot, downy mildew, stemcanker, Rhizoctonia root rot, and Phytophthoraroot rot on soybean; black shank, soreshin, targetspot, frogeye leaf spot, weather fleck, andfrenching on tobacco.
On fruit and vegetable samples, we havediagnosed black rot on grape; Phomopsis leaf
blight on strawberry; cane and leaf rust onblackberry; bitter rot, black rot, cedar-apple rust
and frogeye leaf spot on apple; brown rot onpeach; anthracnose and Rhizoctonia root/stem roton bean; downy mildew on cucumber; bacterialspot and Pythium root rot on pepper;Plectosporium blight on pumpkin; Septoria leaf
spot, bacterial spot, buckeye rot, southern blight,
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Fusarium wilt, and tomato spotted wilt virus ontomato; anthracnose gummy stem blight and
southern blight on watermelon.
On ornamentals and turf, we have seen Pythiumand Rhizoctonia root rots on geranium;
anthracnose on hosta; downy mildew onimpatiens; cedar-quince rust on hawthorn;anthracnose and Botryosphaeria canker on redbud;
Cercospora leaf spot on willow; Pythium rootdysfunction on bentgrass; summer patch on
bluegrass; and brown patch on fescue.
2013 INSECT TRAP COUNTS
July 26 August 2
Graphs of insect trap counts for the 2013 season
are available on the IPM Web site at -http://www.uky.edu/Ag/IPM/ipm.htm.
Note: Trade names are used to simplify the information
presented in this newsletter. No endorsement by the
Cooperative Extension Service is intended, nor is
criticism implied of similar products that are not
named.
Location Princeton, KY Lexington, KY
Black cutworm 20 0Armyworm 3 63
European corn
borer
0 1
Corn earworm 0 1
Southwestern corn
borer
58 0
Fall armyworm 0 0
http://www.uky.edu/Ag/IPM/ipm.htm.http://www.uky.edu/Ag/IPM/ipm.htm.http://www.uky.edu/Ag/IPM/ipm.htm.