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Rhizoctonia Blight, Scourge Of Rice And Soybeans, Also Affecting Corn R


hizoctonia solani AG1-1A, the same pathogen that causes sheath blight in rice and aerial blight in soybeans, is also infecting corn in spots along

the Arkansas River Valley, said Rick Cartwright, ex- tension plant pathologist with the University of Arkansas Division of Agriculture. Rhizoctonia sheath blight can rot corn stalks, often

associated with other infected leaf bases and nodes, and may interact with other stalk-rotting diseases. “I have rarely seen sheath blight at severe enough

levels to cause field-wide yield loss, but I have seen some yield loss in heavily affected parts of fields due to the loss of active leaves and sheaths, combined with increased lodging,” he said. The blight is driven by rotation, and is often worse in

rice-soybean-corn rotations with high-yield histories, low potassium-high nitrogen systems and dense plant populations. “I have seen it progress up the sheaths to the tassels

on isolated plants, and have noted it to be worse in twin-row and high-population plantings with dense canopies, and in fields with low potassium soil levels, where adequate potassium fertilization was not prac- ticed,” said Cartwright. Severity, as with rice, is determined by incidence, or

the number of infected plants per acre, and the per- centage of plant height, or tissue, damaged by the dis- ease. “In rice, we have noted that fields with an average of

10 to 15 percent infected tillers at midseason have the potential to develop sheath blight severity by season’s

Heritage Day, Antique Tractor Adventure Set July 30-31


his year’s Heritage Day and River Hills Antique Tractor Adventure is set for the weekend of July 30-31.

The event begins with a Farmer’s Appreciation So-

cial Hour at 5 p.m. on Friday, July 30, at the Semi- nary Picnic Grounds. Dinner will be served at 6:30. Guest speaker will be Mr. Richard Guebert, a well

known Illinois farmer and vice-president of the Illi- nois Farm Bureau Association.

end that may reduce yield to a measurable level,” he said. “I would guess that fields with 10 to 15 percent or

more infected corn stalks and symptom height at ear leaf prior to milking may suffer minor yield loss, and under the right conditions, could lodge more than fields not affected.” Fungicides have not been recommended to treat

Rhizoctonia blight in the past, but in rare circum- stances they may be considered, said Cartwright. “Azoxytrobin is the most effective fungicide in cur-

rent use against this Rhizoctonia, although other strobilurins like pyraclostrobin and trifloxystrobin may be adequately effective,” he said. Azoxytrobin is the active ingredient in Quadris fun-

gicide and a component of Quilt and Quilt Xcel. Four- teen fluid ounces of Quilt contain 4 fl oz of Quadris, which will have little effect on Rhizoctonia, said Cartwright. “A minimum of 6.4 fluid ounces of Quadris or its

equivalent in Quilt or Quilt Xcel is the minimum to control Rhizoctonia sheath blight in crops for a period of 14 days or so,” he said. Coverage is essential. This may be difficult to achieve

in thick corn fields that are already at silking, as the upper canopy may absorb the bulk of the spray, said Cartwright. “Sometimes dew movement downward or even rain-

fall may redistribute the fungicide to the lower part of the plants, but on corn plants this is not well under- stood,” he said. “Our observation has been that we are only getting foliar disease control in the upper half of the corn canopy in many fields, indicating inadequate application methods in these thick corn fields.”

Smart irrigation starts with


Smart irrigation starts with Zimmatic

(Above) This shot clearly shows sheath blight lesion.

(Left) These stalks clearly

show sheath blight. University of Arkansas Division of Agriculture photos.

“Currently, we still

consider this disease minor in our state, but with the advent of new hybrids with unknown susceptibility,

these higher population sys-

tems and cutbacks in fertilization on some farms, it seems to be on the increase.” For more information on crop production, contact your county extension office or visit

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HURRY! THESE OFFERS END JUL HURRY! THESE OFFERS END JULY 31ST. *Service only. Phone not included. Financing only available in the U . Phone not included. Financing only available in the U.S.

Offer does not apply to previous purchases. Certain restrictions and limitations apply. Valid on orders received by 7/31/10 and shipped by 8/31/10.

Photo of 2009 drivers and tractors getting ready to leave the Seminary grounds. 2009 was the 7th Annual River Hills Antique Ride. Max Armstrong and the Australians with their tractors were with us. This year’s ride will be July 31.

Those who attend can see some of the antique trac-

tors parked on the grounds for view on Friday evening. On Saturday, July 31, the tractor ride will leave the

seminary grounds at 8:30 a.m. and travel through the beautiful Perry County hills and river bottoms, winding around corn, soybean and hay fields. The ride will end at the seminary grounds between 3:30 p.m. and 4:30 p.m. Those interested in attending the Friday evening

events should contact the Perryville Chamber of Com- merce office at 573-547-6062. To participate in the tractor ride contact Marsha

Lappe after 7:30 p.m. at 573-788-2766, or Davis Farm Supplies at 573-547-4556.

© 2010 L ndsay.. All rights reserved. Zimmatic is a egiste ed trademark of the Lindsay Corporation. Certain restrictions and conditions apply.

© 2010 Lindsayi All rights reserved. Zimmatic is a rregisterred trademark

of the Lindsay Corporation. Certain restrictions and conditions apply See your local Zimmatic dealer for complete details.



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July 23, 2010 / MidAmerica Farmer Grower • 13

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