kentucky pest news, august 6, 2013

8/22/2019 Kentucky Pest News, August 6, 2013

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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


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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.

pdf

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.pdf


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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]


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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.pdf


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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.

kentucky pest news, august 6, 2013

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