Mississippi County

Wheat Management 

Wheat production information is available on the web at: http://www.psu.missouri.edu/cropsys/Wheat

This web page contains variety performance testing from several Universities along with general production information.  The 2004 University of Missouri Crop Performance books are in the office, also.  Another good reference available is a $3.00 Wheat Production Guide that the University published this past winter.  When selecting a variety consider yield potential, test weight, disease and insect package, heading date and maturity date.

Consider the quality of the wheat seed you select.  If you plan to use saved seed be sure it is properly cleaned.  Cleaning the seed will remove small and/or shrunken kernels, which may be infected by seed-borne pathogens.  You may also want to consider a fungicide seed treatment.  It is also recommended to have a germination test done.  Knowing the germination rate will allow for accurate seeding rates.   Typically, wheat with a germination below 80% should be avoided.  Seed quality also includes seed size based on thousand kernel weight (TKW).  If possible select a seed with a TKW of 30 grams or higher because these seeds tend to have increased fall tiller number and seedling vigor. 

 Wheat does not tolerate wet feet, therefore select well drained fields and improve drainage in wet spots.   Applying 15-25 lbs of nitrogen along with P and K following corn, grain sorghum or rice can improve crop health and root system.  Phosphorus is essential for good fall and early spring growth.  Target P level for wheat is 45 lb P/Acre.  If unsure of your soil nutrient levels consider having your soil tested.

Optimum planting date can be a challenge and is dictated by weather and harvest of previous crop.  With this in mind, The University of Kentucky recommends a planting date period of October 10 through October 30 for Kentucky.  The University of Missouri’s optimal planting date is based on Hessian fly free date which is October 14.  Wheat planted prior to this date is at increased risk of yield loss associated with Hessian fly, aphid feeding, barley yellow dwarf virus as well as excessive fall growth which increases the risk of spring freeze injury.  Another date to consider is the average first frost which for Mississippi County is approximately October 30.  Although wheat will germinate in soil temperatures as low as 40 degrees, planting later than November 1 increases the risk of poor fall tiller development, winter injury, and heaving. 

An optimal final fall stand should be approximately 35 plants per square foot. To obtain an optimal stand, base seeding rate on seeds per acre which should be between 1,300,000 to 1,500,000 million seeds per acre.  Ideal seed placement is between 1 and 1.5 inches deep when soil moisture is adequate.

Wheat Weed Management

Fall is the best time to identify and control ryegrass and cheat.  When scouting, keep in mind that, in general these weeds will be heaviest near the borders and ditches.  Grass identification can be difficult for anybody.  The following descriptions could help you identify these grass weeds based on a couple key characteristics.  For more details or help on identifying these weeds feel free to contact your local Extension office.

Ryegrass has a “diesel-wash” appearance from a distance, and, in general, is a smooth plant (no hair).  Hoelon (diclofop) and Achieve (tralkoxydim) have been labeled for ryegrass control for several years and are strictly grass herbicides. A newly labeled chemical is Osprey (mesosulfuron) from Bayer.  Osprey controls ryegrass and picks up some other winter annual broadleaves. This new chemical will also aid in ryegrass resistant to Hoelon and Achieve, since it is a different mode of action.  Another herbicide with the same mode of action as Osprey is Finesse (chlorsulfuron+metsulfuron) by DuPont.  Finesse is a preemergence product which offers fair control of ryegrass and also aids in controlling garlic.  However, Finesse’s has rotation restrictions where only  STS soybeans should be planted to avoid injury. 

Unlike ryegrass, cheat, in general, is hairy.  Sencor (metribuzin) is labeled for tolerant wheat varieties but must be timed properly.  A fall application of 2 to 3 ounces of Sencor per acre will provide some control of young cheat with a reduced chance of injury to wheat.  Apply Sencor  to 1 to 3 inch cheat and after wheat plants have 2 leaves and 1 inch secondary roots.  Another option labeled for wheat to control cheat in the fall is Maverick (sulfosulfuron) by Monsanto.    Maverick like Finesse has a rotation restriction where STS soybeans should be planted to avoid crop injury. 

The key to preventing grass weeds from becoming a problem in the spring is to start scouting shortly after wheat emergence and applying the necessary product in the fall.  Fall weed control also reduces competition for wheat going into the winter.  It is also very important to rotate modes of action in order to prevent the spread of resistance.  As always, with any product read the label carefully.

Wheat Insect Management

In the fall, the primary concern  is aphid management.  There are four species of aphid that could potentially attack wheat.  These include the greenbug, English grain aphid, Bird cherry-oat aphid and the corn leaf aphid. 

The greenbug can be a serious pest in wheat because of the toxic saliva it injects into the plant producing yellow leaves and chlorotic spots.  The greenbug can be identified by it’s pale yellow body and dark stripe down the back.  More recent research conducted at Missouri indicates that thresholds for aphids are closer in line to Kentucky’s action thresholds for aphids.  Kentucky’s threshold for greenbug is 10 per row foot. Check out Missouri’s research on the web at: http://www.psu.missouri.edu/cropsys/Wheat/MU_Small_Grain_Extension_and_Research.htm

The biggest threat that English grain and bird cherry-oat aphids pose in the fall is the transmission of Barley Yellow Dwarf Virus (BYDV).  However, controlling aphids at threshold levels is only a small part in reducing the risk of potential BYDV infection.  Management also should include destroying any volunteer wheat or grass weeds in the field, avoiding an early planting date in order to minimize the window that insect vectors can transmit viruses to young plants, and maintaining good plant vigor.   English grain aphids are pale green with long black antennae and cornicles.  Bird cherry-oat aphids have a mottled, yellowish to olive green to black coloration with black antennae and legs plus a red patch at the base of the cornicles.  One approach to BYDV management focuses more on timely planting to reduce the amount of time for aphid populations to build up in the fall.  Again recent research from Missouri suggests that yield could be negatively influenced when aphid populations are above 5 per row foot in the fall.  Kentucky action thresholds for aphid management when BYDV is a concern are based on crop age.  30 days after emergence (DAE) - 3 aphids/row ft; 30-60 DAE - 6 aphids/row ft; 60+ DAE - 10 aphids/row ft.

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		University of Missouri Extension Mississippi County mississippico@missouri.edu Updated 05/24/04