kentucky pest news, august 21, 2012

7/31/2019 Kentucky Pest News, August 21, 2012

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Online at:www.uky.edu/KPN

Number 1315 August 21, 2012

CORN

-Harvesting and Storing Kentucky's 2012 Corn

Crop

-Fusarium Ear Rot and Fumonisins-Scouting Corn for Aspergillus Ear Rot

SOYBEAN

-Armyworm / Fall armyworm Problems Increase

DIAGNOSTIC LAB HIGHLIGHTS

INSECT TRAP COUNTS

CORN

Harvesting and Storing Kentucky's 2012

Corn CropBy Sam McNeill, Extension Agricultural

Engineer and Paul Vincelli, Extension Plant

Pathologist

USDAs mid-August crop report1

predicted corn

yields for Kentucky of 65 bushels per acre,

which is less than half of last years crop and

due largely to drought conditions. Even though

more corn acres were planted than 2011, the

forecast for the states production is just under97 million bushels, which is about 46% of last

years total. Any time drought stresses a crop

there is always a concern that aflatoxin or other

mycotoxins may develop in the field or after

harvest if its not dried quickly or stored

properly. It is important to remember that not

all fungi produce mycotoxins, but individual

kernels with mold or insect damage are more

susceptible than intact kernels. So it is best to err

on the side of caution and check damaged cornlots for mycotoxins before feeding to livestock.

When harvesting damaged corn, adjust

combines to minimize mechanical injury so that

sound kernels are protected. Also, maximizecleaning so that lightweight and broken kernels

are removed. Harvest, handle and store

damaged corn separately when feasible and feed

or market early to reduce demands on storage

management.

Grain moistures above 18-20% favor the growthof field fungi and the longer corn remains in the

field, the greater the chance of mycotoxin

production. Thus, damaged corn should not be

allowed to dry in the field to avoid drying

costs. Instead, it should be dried with heated airto 15% within 24 hours after harvest and cooled

to 45 degrees as soon as weather permits, in

order to control mold growth during

storage. This will create a storage environmentwithin the grain mass that is below 65%

humidity, which is dry enough to control mold

growth and development (see values in theequilibrium moisture table).

TemperatureF

Relative Humidity, %

45 55 65 75 85

Corn Moisture, %

40 12.2 13.7 15.3 17.2 19.6

50 11.6 13.1 14.7 16.5 18.9

60 11.1 12.5 14.1 15.9 18.3

70 10.6 12.0 13.6 15.4 17.7

Figure 1

Corn with heavy to moderate damage should be

dried to 12 to 13%, respectively, cooled as

quickly as possible and moved before March.

Some standing corn has already dried to this

level in some parts of Kentucky.

If mycotoxin problems are suspected, check with

crop insurance providers to see if adjustments

Lexington, KY 40546
http://www.uky.edu/KPNhttp://www.uky.edu/KPNhttp://www.uky.edu/KPNhttp://www.uky.edu/KPN


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may be needed and how to account for the areas

that are impacted. Insurance adjustments

generally need to be made on standing corn at or

before harvest.

Information on scouting corn fields for

Aspergillus ear rot and other field molds prior toharvest was provided in the August 14 issue of

Kentucky Pest News (No. 1314). See the current

issue for information on scouting for Fusariumear rot. The following publications provide

more information on fumonisins, aflatoxins and

grain testing labs:

http://www.ca.uky.edu/agc/pubs/id/id121/id121.

pdf

http://www.ca.uky.edu/agc/pubs/id/id59/id59.pd

f

http://www.ca.uky.edu/agcollege/plantpathology

/ext_files/PPFShtml/PPFS-MISC-1.pdf1http://www.nass.usda.gov/Statistics_by_State/K

entucky/Publications/Agri-

News/Aug_2012_web.pdf

Fusarium Ear Rot and FumonisinsBy Paul Vincelli

Pre-harvest contamination of corn withfumonisins is a possibility in some lots of this

years Kentucky corn crop. Fumonisins are a

family of mycotoxins produced by the fungus

that causes Fusarium ear rot. These natural

toxins have the potential to cause lethal diseases

of horses and swine (the diseases are equine

luekoencephalomalacia and porcine pulmonary

edema, respectively). Pre-harvest contamination

of corn by fumonisins is most often associatedwith drought stress at the silking stage, a stress

that occurred widely in Kentucky and beyond.

Symptoms of Fusarium kernel rot usually occur

scattered throughout the ear on individualkernels or groups of kernels. Kernels affected

by Fusarium kernel rot often exhibit salmon-

pink to reddish discoloration on uninjured kernel

caps. The rot is often associated with kernel

injury, although unwounded kernels can beaffected.

Once symptoms develop, if there is moisture

under the shuck, the fungus can continue tospread and form a heavy cottony fungal growth

that can consume the entire ear. Maturing ears

which point upright during a heavy rain, would

be at risk of extensive rotting.

It is advisable to scout corn fields for evidence

of Fusarium ear rot, by walking fields and

peeling the shuck of a sample of ears. Fields

with moderate to high levels of Fusarium ear rot

should be considered for harvest at 25-27%

moisture content and drying to below 15%

within a day or two of harvest.

Unfortunately, it is difficult to say how muchFusarium ear rot is too much in a given field,

since mycotoxin levels in grain often dontcorrelate well to amounts of kernel rot.

However, if 2-5% or more of the ears have

symptoms like those figures provided in this

article, that would probably justify a quick

harvest/dry-down. A dry-down may be

especially justified for lots destined for food use,

just from the quality-control standpoint.

While scouting for Fusarium ear rot, also look

for olive-green mold typical of Aspergillus ear

rot, especially on knolls of hills or other

droughty areas. Aspergillus ear rot can result inaflatoxin contamination (see article from last

week). This ear rot is most likely when corn is

subject to severe drought stress during grain fill.

Questionable lots of corn should be tested for

mycotoxins before feeding, especially to

sensitive animals.

Producers should be aware that fumonisins canoften be found at higher concentrations in

injured and broken kernels than in sound

kernels. Producers who clean their corn areadvised not to feed screenings to livestock, since

these pose the greatest risk. Many of the casesof poisonings of horses and swine from

fumonisins in the Midwest result from feeding

of screenings to livestock.
http://www.ca.uky.edu/agc/pubs/id/id121/id121.pdfhttp://www.ca.uky.edu/agc/pubs/id/id121/id121.pdfhttp://www.ca.uky.edu/agc/pubs/id/id121/id121.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.nass.usda.gov/Statistics_by_State/Kentucky/Publications/Agri-News/Aug_2012_web.pdfhttp://www.nass.usda.gov/Statistics_by_State/Kentucky/Publications/Agri-News/Aug_2012_web.pdfhttp://www.nass.usda.gov/Statistics_by_State/Kentucky/Publications/Agri-News/Aug_2012_web.pdfhttp://www.nass.usda.gov/Statistics_by_State/Kentucky/Publications/Agri-News/Aug_2012_web.pdfhttp://www.nass.usda.gov/Statistics_by_State/Kentucky/Publications/Agri-News/Aug_2012_web.pdfhttp://www.nass.usda.gov/Statistics_by_State/Kentucky/Publications/Agri-News/Aug_2012_web.pdfhttp://www.nass.usda.gov/Statistics_by_State/Kentucky/Publications/Agri-News/Aug_2012_web.pdfhttp://www.nass.usda.gov/Statistics_by_State/Kentucky/Publications/Agri-News/Aug_2012_web.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id121/id121.pdfhttp://www.ca.uky.edu/agc/pubs/id/id121/id121.pdf


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Sources of Additional InformationMore information on fumonisin is available in

the UK Extension publication ID-121,

Fumonisin, Vomitoxin, and Other Mycotoxins in

Corn Produced by Fusarium Fungi, available at

http://www.ca.uky.edu/agc/pubs/id/id121/id121.

pdf.

More information on aflatoxins is available in

the publication ID-59,Aflatoxins in Corn, at

http://www.ca.uky.edu/agc/pubs/id/id59/id59.pdf.

Some of the laboratories where mycotoxin

testing is performed include those listed in:


/ext_files/PPFShtml/PPFS-MISC-1.pdf

Commercially available rapid test kits formycotoxin testing are listed at:

http://www.gipsa.usda.gov/fgis/tech-

servsup/metheqp/testkits.pdf.

Figure 2. Typical symptoms of Fusarium ear and kernel

rot. Note whitish fungal growth. Usually damage from

Fusarium ear rot affects scattered kernels or groups of

kernels, as shown here.

Figure 3. Fusarium kernel rot at ear tip. Note white

fungal growth. Also note association with insect injury.

Figure 4. Fusarium ear and kernel rot. This rot normally

doesn't progress from the base of the ear, but it is

possible, as shown here.
http://www.ca.uky.edu/agc/pubs/id/id121/id121.pdfhttp://www.ca.uky.edu/agc/pubs/id/id121/id121.pdfhttp://www.ca.uky.edu/agc/pubs/id/id121/id121.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.gipsa.usda.gov/fgis/tech-servsup/metheqp/testkits.pdfhttp://www.gipsa.usda.gov/fgis/tech-servsup/metheqp/testkits.pdfhttp://www.gipsa.usda.gov/fgis/tech-servsup/metheqp/testkits.pdfhttp://www.gipsa.usda.gov/fgis/tech-servsup/metheqp/testkits.pdfhttp://www.gipsa.usda.gov/fgis/tech-servsup/metheqp/testkits.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id121/id121.pdfhttp://www.ca.uky.edu/agc/pubs/id/id121/id121.pdf


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Scouting Corn for Aspergillus Ear RotBy Paul Vincelli

Aflatoxins are potent, naturally occurring toxins

that sometimes develop in corn and certain other

crops. Aflatoxins are also among the most

carcinogenic substances known. There are well-defined limits on how much aflatoxin is

allowable in corn, based on the intended end

use. For example, corn intended for humanconsumption must have less than 20 ppb (parts-

per-billion!). More information on aflatoxin can

be found in the UK Extension publication,

Aflatoxins in Corn, ID-59, at

http://www.ca.uky.edu/agc/pubs/id/id59/id59.pdf

The prevalence of drought conditions this

growing season is resulting in aflatoxin

contamination in at least a few sporadicinstances. Some Extension agents have

expressed interest in informally scouting for the

problem in advance of harvest. This is an

excellent idea. The problem is, it is very

difficult to assess standing corn crops for

aflatoxin contamination. Some of the reasonsfor this include:

The mold associated with aflatoxin maynot always be visible in contaminated

grain.

The presence of the mold does not meanaflatoxin is present.

There are several green molds on corn,and they can be hard to tell apart.

Even when it occurs, aflatoxin iscontamination is very sporadic for lots

of reasons, so a grower may have veryhigh levels in one field and low levels in

another.

Having now lowered expectations, I do think

scouting is a good idea, especially this year. Itmight help producers manage their risks a little

more wisely.

The scouting approach that makes the most

sense to me is to visually inspect the ears formold typical of Aspergillus ear rot. Scouting

can be done any time after black layer. Pay

special attention to the driest parts of the field.

Usually the disease appears as olive-green mold

(Figures 1-4). The moldy growth appears

powdery, the result of the massive numbers of

spores produced by the fungus. The spores are

dispersed easily in the air, and they may appear

as fine dust when the husk is pulled back. The

mold is commonly found at the tip of the ear, butas you can see from the photos, it may be found

anywhere on the ear, especially where physical

injury occurs to the kernels.

Other ear molds of corn are caused by fungi that

produce various powdery molds, including green

molds. Trichoderma ear rot is more greenish

than the olive-green typical of Aspergillus

(Figure 5). Penicillium kernel rot can be quite

common on injured kernels (Figure 6), but that

mold tends towards a blue-green color than

olive-green.

What should you do if you suspect a case of

Aspergillus ear rot? We can confirm the causal

fungus in the UK diagnostic labs, which may beuseful in deciding whether to test for aflatoxins.

Butplease bag the sample and inform the labthat it is a suspect case of Aspergillus ear rot, so

that the staff can protect themselves by handling

the sample in a biosafety cabinet.

UK doesnt offer a routine testing service for

aflatoxin, but there are numerous laboratoriesthat are equipped to analyze corn samples. Alist of laboratories is available at


/ext_files/PPFShtml/PPFS-MISC-1.pdf. This is

an incomplete list; other competent labs exist,

but this will serve as a handy reference of some

of the available laboratories.

This is a really important point: If you properly

collect 10 samples from a moving stream of

grain (see ID-59), aflatoxin quantity will vary

quite a bit among those 10 samples. That is thenature of sampling for a chemical present at

parts-per-billion levels. This variability will be

even worse if you are submitted ears collected

while scouting. Look at Table 1 in ID-59

(http://www.ca.uky.edu/agc/pubs/id/id59/id59.p

df.) to understand just how variable sampling for

aflatoxin can be, even when done according to

best practices.
http://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-MISC-1.pdfhttp://www.ca.uky.edu/agc/pubs/id/id59/id59.pdf


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As far as to do with the information from

scouting, see ID-59 for helpful ideas.

Figure 5. Aspergillus ear rot, Alison Robertson, Iowa State

University, http://www.ipm.iastate.edu/ipm/icm/2005/9-19/aflatoxin.html

Figure 6. Aspergillus ear rot, from University of Illinois,

http://cropdisease.cropsci.illinois.edu/corn/Aspergillusearr

ot.html

Figure 7. Aspergillus ear rot, from Iowa State University,

http://www.ipm.iastate.edu/ipm/icm/node/226

Figure 8. Aspergillus ear rot, Purdue University,

http://www.extension.purdue.edu/extmedia/BP/BP-83-

W.pdf


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.

Figure 9. Trichoderma ear rot

Figure 10. Penicillium ear rot, photo University of Illinois,

http://bulletin.ipm.illinois.edu/article.php?id=1244

SOYBEAN

Armyworm / Fall armyworm Problems

IncreaseBy Doug Johnson, Extension Entomologist

Feeding of one or several armyworm speciesappears to be on the increase. I cannot be

completely sure which species are causing the

damage, and it is likely that two species, the

armyworm also know as True armyworm and thefall armyworm are the most likely culprits.

Fall armyworm moth captures in the IPM

pheromone baited traps at Princeton, KY have

skyrocketed in the last two weeks, going from 0 to

131 and currently to 550 moths captured in the

trap week ending 9/16/12. In addition several

people have reported large populations of wormsmoving from grass to soybeans over the last week.

Just today (8/17/12) one location in Caldwell Co.

KY was reported to be infested at a rate of 20

worms per square foot! These are likely fall

armyworm, but unfortunately I have not been able

to examine these pests.

Regardless of which species of armyworm is

active in your area the management will be the

same. See the article on fall armyworm in the

previous issue of this news letter for control

considerations (Johnson, D. Aug. 14, 2012. Fallarmyworm flight increases. KPN No. 1314).

Given the large increase in moth captures, and the

large number of fields with late developing

soybeans, this problem is likely to continue for

some time.


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DIAGNOSTIC LAB HIGHLIGHTS

By Julie Beale and Paul Bachi

Agronomic samples during the past week

included smut on corn; brown stem rot,

charcoal rot, Rhizoctonia root rot, suddendeath syndrome, soybean cyst nematode and

poor nodulation on soybean; black shank,

frenching, Fusarium wilt and tomato spotted

wilt virus on tobacco.

On fruit and vegetable samples, we have

diagnosed Botryosphaeria canker onblueberry; heat injury on grape; bitter rot on

apple; Alternaria leaf blight on cantaloupe;

powdery mildew on pumpkin and squash; root

knot nematode on potato; anthracnose,Septoria leaf spot and Fusarium wilt on

tomato.

On ornamentals and turf, we have seen rust on

aster; charcoal rot on hollyhock; Rhizoctonia

root/stem rot, Fusarium wilt and web blight onchrysanthemum; Rhizoctonia root/stem rot

and black root rot on petunia; Rhizoctonia and

Pythium root rots on annual vinca; black rootrot on holly; take-all patch and cottony blight

on bentgrass; summer patch on bluegrass; and

brown patch on fescue.

INSECT TRAP COUNTS

August 9 - 15

Graphs of insect trap counts for the 2012season are available on the IPM web site at -

http://www.uky.edu/Ag/IPM/ipm.htm.View trap counts for Fulton County, Kentucky

at -

http://ces.ca.uky.edu/fulton/InsectTraps

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,

KYBlack cutworm 5 0

Armyworm 30 0

Corn earworm 189 11

European corn

borer

9 0

Southwesterncorn borer

519 0

Fall armyworm 549 0

kentucky pest news, august 21, 2012

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