Published: September 06, 2008 11:00 pm         

OSU Extension Notes 09-07-08

Ag News

Tuesday Gardening Series

Garden Cleanup, Composting, and Winter Cover Crops

Sept. 9 from 6-7:30 p.m. in Heritage Hall of the Payne County Expo Center. Free and open to the public. Call 747-8320 for more information.

Fall Army Worms Have Moved Into Oklahoma

Tom Royer, extension entomologist at Oklahoma State University has received numerous reports of heavy fall armyworm infestations in sorghum fields throughout Oklahoma during the latter part of August. He recently received a report of fall armyworms attacking grass pastures in southern Oklahoma. Royer says these reports suggest that we could see a larger generation in early to mid September that could cause some serious problems for grass pastures, seedling wheat and some residential lawns.

Fall armyworms are caterpillars that directly damage sorghum heads, fescue and bermudagrass pastures, seedling wheat, soybean and residential lawns. Since they do not overwinter in Oklahoma, fall armyworms tend to occur later in the summer as populations build up in Gulf States and adult moths migrate northward. Female fall armyworm moths lay up to 1,000 eggs over several nights on grasses or other plants. Within a few days, the eggs hatch and the caterpillars begin feeding. Caterpillars will complete a generation in 18-28 days and molt six times.

Newly hatched fall armyworms are white, yellow, or light green and darken as they mature. Mature fall armyworms measure 1.5 inches long with a body color that ranges from green, to brown to black. They can be distinguished by the presence of a prominent inverted white “y” on their head.

However, infestations need to be detected long before they become fully mature caterpillars. Small larvae do not eat through the leaf tissue, but instead, scrape off all of the green tissue and leave a clear membrane that gives the leaf a “window pane” appearance. After the larvae have molted four times, they can completely consume leaf tissue. It is at this stage that they cause most of the serious damage to a grass pasture or lawn.

An Auburn University entomologist developed an easy-to-use scouting aid for pasture that consists of bending a wire coat hanger into a hoop, placing it on the ground and counting fall armyworms in the hoop. Examine plants at several locations along the field margin as well as in the interior. Look for window-paned leaves and count all sizes of larvae. The hoop covers about 2/3 of a square foot, so a threshold in pasture would be an average of 2- or 3-inch-long larvae per hoop sample.

“Don’t take a chance on losing a grass crop,” Royer says. “This method is simple, effective, and can help a producer get a head start on managing a potentially devastating fall armyworm infestation.”

Royer says that smaller caterpillars (1/2 inches long or less) should be targeted for control for two reasons. First, the caterpillars don’t cause severe damage until they reach 1 inch long, and secondly, smaller caterpillars are much more susceptible to insecticide control than larger caterpillars.

Nathan Anderson offers a final reminder: “Our growers won’t escape the potential danger from fall armyworms until we get a good killing frost, so they should not let their guard down.”

For control options, consult OSU Fact Sheet CR-7193; Management of Insect Pests in Rangeland and Pasture. If you have any questions about this problem and specific control suggestions, contact Nathan Anderson at the Payne County Extension office 747-8320.

Wheat Varieties for NE Oklahoma

In 2008 the top four grain yielding wheat varieties at the Eastern Research Station near Haskell included Oklahoma varieties Endurance and Duster, AgriPro variety Fannin and Kansas variety Fuller. Dr. Jeff Edwards, state extension small grains specialist suggests that Westbred varieties Shocker and Santa Fe might also be worth looking at if shopping for new varieties.

Looking for dual purpose wheat for both grazing and grain? Then two to consider are Endurance or Duster for their excellent high temperature germination tolerance and medium to late appearance of first hollow stem. Fannin also performed will in forage trials averaged over two years at Stillwater and El Reno but first hollow stem occurred 15 and 18 days earlier than Duster or Endurance. This means cattle would need to be removed from Fannin at least two weeks earlier than Duster or Endurance.

A complete list of the Oklahoma wheat variety performance trials and a wheat variety comparison chart is available at the following website http://www.wheat.okstate.edu/.

Managing Nitrogen on Wheat

The traditional method of managing nitrogen applications on wheat was to apply two pounds of nitrogen for every bushel of wheat expected in a yield goal. A 50-bushel yield goal would require 100 pounds of nitrogen per acre. Typically, part or all of this nitrogen was applied in the fall and the remaining would be applied as a topdress application in the spring prior to jointing.

The old methods have served us well but just like tractors, combines, varieties or herbicides, new technology offers us a way to improve on the old method.

This new technology uses optical sensors to monitor a nitrogen ramp or nitrogen rich strip in each wheat field. The benefit comes from being able to adjust nitrogen rates to environmental conditions during the growing season and conditions within a specific field. There are wheat growers in northeast Oklahoma who have used this technology multiple years and have reported an improvement in their economic yield.

With nitrogen at or above $1 per pound, farmers producing wheat for grain should take a serious look at this new technology for improving their nitrogen use efficiency. All it takes is a nitrogen rich strip in every wheat field at or before planting. The nitrogen rich strip could be applied with a fertilizer applicator by making an extra pass or two in a small area or across the field or by hand with a coffee can and a bag of nitrogen fertilizer.

Sensor readings for determining the amount of topdress nitrogen needed are collected from each field after 80 growing degree days have accumulated since planting. The growing degree days can be monitored at http://agweather.mesonet.org/ and will normally occur in February. GreenSeeker sensors for collecting the information called NDVI’s are located in several northeast Oklahoma counties.

Soil tests are still needed to determine the amount of phosphorus, potassium, or lime required for efficient crop production. A subsoil nitrate test is also recommended. With a current soil test and using the sensor technology your county educator will be equipped to assist you identifying cost saving opportunities and achieving optimum economic yields.

To find out more about this new technology for improving your nitrogen management on this year’s wheat crop contact your local County Extension Educator. More information is also available online at http://nue.okstate.edu/.

Reducing Cattle Transportation Losses

During the fall months, many calves in northeast Oklahoma are weaned. This process usually includes being loaded on trailers (trucks) to be moved to market or some other location for pasture.

Loading too few or too many animals on a trailer can result in injuries. Too many times, not enough thought and care is put into the trailer space requirements necessary to move a given number of cattle. Also, cattlemen tend to underestimate the stress and subsequent sickness that can be imposed on cattle when improperly loaded.

Every type and size of beef animal possible will be moved on every type and size of trailer imaginable. It is difficult for cattlemen to know what the right fit is. How many of my calves weighing about 450 pounds will fit in a 6-foot-by-20-foot stock trailer?

As a rule of thumb each square foot of trailer floor space can hold 65 pounds of calf (350-600 pound range) weight. Therefore, one could safely load and haul about 17 head in this example. Each calf requires 6.92 square feet (450 pounds divided by 65 pounds equals 6.92) and in this particular trailer there are 120 square feet available for hauling (120 divided by 6.92 equals 17.33). With cows, 75 pounds per square foot can be safely hauled.

Typically, the weight of cattle being loaded is unknown. The above guidelines along with an estimated weight are helpful when planning transportation for cattle. In the end, the manager must observe the cattle on the trailer. When properly loaded, animals will fit easily into the compartment for hauling, but the entire area will appear occupied.

Trucking Tips

1. Use partitions to separate different classes and weights of cattle transported on the same trailer.

2. Make certain the floor of the trailer provides cattle with good footing. This is important to reduce shrink and injury.

3. Check trailer load regularly during the trip.

4. Accelerate vehicle smoothly and avoid sudden stops.

(Adapted from GPE-3050)

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