Severe cases of fumonisin contamination are showing up
in some instances in this year's corn. Fumonisins are a
class of mycotoxins (toxins produced by fungi) which
cause toxicity to horses, swine, and other animals. There
is also concern about possible detrimental health effects
of fumonisins to humans. Fumonisins commonly are
produced by the fungus Fusarium verticillioides, the
fungus that causes Fusarium ear rot.
Fumonisins do not occur widely in Kentucky, but contamination of corn can sometimes develop in the field. Although fumonisin contamination in the field is often associated with hot, dry weather prior to and during silking, it also has been reported following late- season rains on corn where harvest has been delayed.
Several corn lots from the 2004 crop are showing test values of 55-108 ppm fumonisins, as determined by the UK Grain Quality Testing Laboratory. I suspect that the frequent wet weather experienced in many areas this summer may have favored fumonisin contamination by allowing unusually high levels of growth of F. verticillioides under the husk during late grain-fill, especially if left standing in the field. Hybrids with ears maturing in an upright position may have been at a particular risk, because they would collect and hold rainfall more than downward-pointing ears.
If there are still corn fields awaiting harvest, they should be harvested as soon as possible and dried to no more than 15.5%% MC. Proper drying and storage is needed because contamination can also occur under improper storage conditions. If there is ay doubt about the condition of corn already in storage, it should be inspected for mold and tested at the UK Grain Quality Testing Laboratory.
More information on fumonisins in corn is available online at http://www.ca.uky.edu/agc/pubs/id/id121/id121.pdf ..... Grain storage recommendations are available in the Extension publication, Principles of Grain Storage (AEN-20).
For information about corn pests, visit
"Insect Management Recommendations".
A group of researchers has identified a source of
resistance for use in soybeans against the soybean aphid.
This pest, first found in the U.S. in 2000, has caused
many problems in the upper Midwest and is now found
throughout most of the U.S. soybean production area,
including Kentucky.
Soybean aphid has not been a major pest in Kentucky but it certainly has the potential to cause many problems for us, including direct feeding, and movement of important plant viruses. Having watched this pest for the past four years, we do know that it can reach Kentucky's entire soybean production region each season. We will be watching this pest for a great many years to come.
Here are some highlights of the article: "Researchers Identify Gene with Resistance to Soybean Aphids":
"This gene has been tested in both the greenhouse and the field and has consistently prevented colonization by soybean aphids,…",
"Because it is a single dominant gene with identified DNA markers, it can be readily introduced into susceptible commercial soybean varieties by backcrossing using marker-assisted selection.",
"The methods for breeding plants with the aphid- resistance gene will be licensed for use in both public and private breeding programs.",
All current commercially available soybean varieties are susceptible to the soybean aphid,
Resistance was found in two different cultivars, called Jackson and Dowling, which are old varieties formally grown in the south, the resistance is confirmed to be conferred by a single major gene,
Moving the gene into adapted soybean varieties and testing whether there is any associated yield or agronomic drag associated with the gene is the next step,
Soybean breeders hope to have resistance in the seed market by 2008.
The news release may be viewed at the following site http://web.aces.uiuc.edu/news/stories/news2857.html
Questions specific to this article should be directed to: Rob Wynstra (217)333-9446, wynstra@uiuc.edu.
Additional details on this technology are available on the Internet at http://www.otm.uiuc.edu/techs/techdetail.asp?id=267
For more information about soybean pests, visit
"Insect Management Recommendations".
When annual ryegrass is seeded in late summer in Kentucky, it can produce a high-quality forage suitable for grazing in late autumn and through most of the spring. However, some recent efforts to use annual ryegrass on dairy- and beef-cattle farms in Kentucky have resulted in failure, due to severe leaf blighting by a disease called gray leaf spot, caused by the fungus Magnaporthe oryzae (also known as Pyricularia oryzae). To the best of our knowledge, this is the same fungus that causes the occasionally severe, widespread epidemics on perennial ryegrass used in turfgrass swards (golf courses, athletic fields, etc).
In recent UK research, we were disappointed to find that all cultivars of annual ryegrass seedlings tested-both diploid and tetraploid-exhibited moderate to high susceptibility to P. oryzae isolates from annual ryegrass. Adult plants also exhibited substantial levels of susceptibility in our tests.
Weather over the past month or so has generally been
favorable for gray leaf spot, with mild, humid weather
and periodic rains. Given this weather pattern and the
susceptibility of the annual ryegrass, there may be
pastures and fields where recent seedings are dying.
This risk would be highest in untilled pastures where
annual ryegrass is sown annually in late summer
following an annual crop. Producers are encouraged to
scout recent sowings of annual ryegrass and involve
your county Extension agent if stands are deteriorating.
Is there something eating on your wheat? Are you sure it
is not rabbits or deer? If not, then it might be Fall
armyworm (FAW). This is a common pest of all grass
crops (pastures, small grains, corn, sorghum, etc.) and it
also feeds on a few broad leaf crops like soybean. This
time of year it is usually limited to new seedings of
grasses (like pasture / hay and reclaimed land) and
small grains.a
FAW migrates into our area each year from the gulf coast area and does not over-winter in Kentucky. However, it can remain active until a solid freeze or at least a very hard frost. Normally, the pest is not much of a factor in small grains but on occasion it can be important.
One might think of this insect as a herd of tiny cattle grazing over the new plants (except they don't weigh as much!). They can remove all the top growth, but will only kill plants that are not yet well established. So, one should be very careful in recommending a replanting. Often this results in a double stand.
There is no real threshold for this pest. In pastures, a general number of 2 or more worms ½" to ¾" long, per square foot is used. Certainly, in high quality small grains, populations should not be allowed to exceed this, unless a killing frost is eminent.
To see a picture of this insect go to:
IPM web pages
http://www.uky.edu/Agriculture/IPM/scoutinfo/wheat/insects/faw/faw1.htm
Also, look at the corn Entfact-110 http://www.uky.edu/Agriculture/Entomology/entfacts/pdfs/entfa110.pdf
And see fall armworm in pasture: http://www.uky.edu/Agriculture/kpn/pdf/kpn_1003.pdf
See "Insect Management Recommendations" for more wheat pest information.
This past growing season has been very favorable for diseases of fruit crops in Kentucky. Most regions of the state had extended wetness periods in spring which favored such fungal diseases as apple scab, grape black rot, and strawberry gray mold as well as many bacterial diseases. Gardeners seeking to improve their chances of disease-free fruit crops next year are posing questions about disease management now while the diseases are still fresh in mind. County Extension Agents may find these questions and answers useful as they consult with gardening clients in the coming weeks.
1. Question: Why do strawberry fruits rot in the
garden?
Answer: Strawberry gray mold, caused by the fungus
Botrytis cinerea, is the most common and serious fruit rot
of strawberry in Kentucky gardens. Prolonged rainy
and cloudy periods during bloom and harvest are very
favorable for disease. Fruit infections usually appear as
soft, light brown, rapidly enlarging decayed areas.
Under moist conditions abundant gray-brown fluffy
fungal growth on infected tissue is visible, giving the
disease its name, gray mold. Other diseases such as
Rhizopus rot, anthracnose and leather rot also decay
strawberry fruits, but gray mold is the most common.
Thinning out strawberry beds to provide better air
movement and sunlight penetration helps reduce gray
mold. In winter, removal of dead leaves and debris from
the bed helps to reduce springtime inoculum. If
fungicides are used, applications made during bloom are
most effective; spraying as fruits are developing and
ripening is wasteful and ineffective. For more
information, consult U.K. Cooperative Extension
publication Gray Mold of Strawberry, (PPA-31).
2.Question : Why do grape berries turn black and
shrivel up in summer even before they ripen?
Answer: Black rot, caused by the fungus Guignardia
bidwellii, consistently destroys grapes in Kentucky,
especially during wet seasons. Although black rot is the
most common, other grape diseases such as bitter rot,
ripe rot, and anthracnose can also cause fruits to turn
black and shrivel up. Diagnosing these fruit diseases
might require the services of a professional laboratory.
Black rot disease is also commonly seen on leaves as
angular, tan spots with dark margins. Fruit infection
begins as a dark rotted spot, but soon spreads to the
entire berry and to other fruits in the cluster. Sanitation
for black rot management begins in winter; fruit
mummies left over from the summer must be removed
from the vines or picked up off the ground and
destroyed. Because of black rot, many grapes are
difficult to grow in Kentucky without the benefit of
regular fungicide applications from bud break until just
before harvest. For more information on black rot
disease management, consult U.K. Cooperative
Extension publications Black Rot of Grapes (PPA-27),
Disease and Insect Control Program for Home Grown Fruit in
Kentucky (ID-21), and Growing Grapes in Kentucky (HO-21
3. Question: What causes peaches and plums to rot
and turn brown just as they are ripening, often
with tan, moldy growth on the rotted fruit surface?
Answer: Brown rot, caused by the fungus Monilinia
fructicola, is a devastating disease of peach, nectarine,
plum, and cherry. In warm, humid, disease-favorable
weather, brown rot disease can destroy a fruit crop
practically overnight. The tan, moldy growth seen on
some decayed fruit consists of spores and mycelium of
the causal fungus. Rotted fruits left hanging in the tree
shrivel up and become mummified, overwintering as
sources of disease for next year. Sanitation, the removal
of mummified fruits from the tree and from the ground
before the next growing season, is an essential step in
brown rot management. Fungicides can be used to help
manage brown rot, but sprays need to be applied from
bloom until almost harvest. For more information on
brown rot disease management, consult U.K.
Cooperative Extension publication Disease and Insect
Control Program for Home Grown Fruit in Kentucky (ID-21)
and Growing Peaches in Kentucky (HO-57).
4. Question: What causes the ends of twigs and
branches of apple trees to die back in springtime,
blackening the leaves sometimes a foot or two back
from the shoot?
Answer: Fire blight often causes infected shoots to turn
brown to black from the ends and bend near the tip to
resemble a shepherd"s crook. This disease, caused by
the bacterium Erwinia amylovora, is very sporadic, killing
many branches or an entire tree one year and perhaps
not causing any symptoms another year. Fire blight
affects apples, pears, and flowering crabapples and
pears. Sanitary measures such as pruning out dead
twigs and branches while the trees are dormant is most
helpful. For more information on fire blight
management, consult U.K. Cooperative Extension
publication Fire Blight (PPA-34) and Disease and Insect
Control Program for Home Grown Fruit in Kentucky (ID-21).
5. Question: What causes the surface of apple fruits to
become dark and sooty by season's end?
Answer: The fungal diseases sooty blotch and flyspeck,
usually occurring at the same time, often cover the
surface of apple fruits by the end of the season in
Kentucky. The diseases are favored by wet, humid
weather and are likely to be found on unsprayed trees.
Sooty blotch appears as gray or dark brown sooty or
cloudy smudges or blotches while flyspeck consists of
aggregates of small, shiny black spots. These blemishes
are superficial and the fruit are still edible, however,
they will not endure long storage as well as healthy fruit.
Thinning the branches of apple trees and pruning
nearby trees which may be shading the apples will
improve air movement and sunlight penetration and
reduce fruit disease For more information on apple
fruit diseases, consult U.K. Plant Pathology fact sheet
Apple Fruit Diseases Appearing at Harvest (PPFS-FR-T-02).
In recent weeks we have diagnosed the following
samples in the Diagnostic lab: Diplodia ear rot on corn;
bacterial pustule on soybean; root knot nematode on
tobacco; anthracnose (ripe rot) on tomato fruits;
anthracnose of liriope; Rhizoctonia root and collar rot on
elm; Botryosphaeria canker on dogwood; Phytophthora
root rot on forsythia and peach; and anthracnose,
Curvularia (fading out), Pythium blight, Pythium root
rot, pink snow mold, and brown patch on turfgrass.
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.
Lee Townsend
Extension Entomologist