Kentucky Pest News Newsletter

HIGHLIGHTS IN THIS ISSUE

Number 1041__________Nov 8, 2004

CORN
FORAGE
FRUIT
SOYBEAN
WHEAT
DIAGNOSTIC LAB HIGHLIGHTS


Corn






CORN



TEST MOLDY CORN FOR FUMONISINS
By Paul Vincelli

Corn 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".


Soybeans

SOYBEAN



RESISTANCE TO SOYBEAN APHID FOUND!
By Doug Johnson

Bean 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".


Hayfield

FORAGE



 

GRAY LEAF SPOT RISK TO NEW ANNUAL RYEGRASS SEEDINGS
By Paul Vincelli

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.


Wheat

WHEAT


 


FALL ARMYWORM ON WHEAT?
By Doug Johnson

FAW 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 " to " 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.


Apples

FRUIT



FRUIT DISEASE QUESTIONS
By John Hartman

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).


Microscope

DIAGNOSTIC LAB HIGHLIGHTS


DIAGNOSTIC LAB - HIGHLIGHTS
By Julie Beale and Paul Bachi

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

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