Summer 1999

On-Site Trap Crop Testing Successful in Reducing Sugarbeet Nematodes

by
Tonya Talbert, Senior Editor
University of Wyoming College of Agriculture

University of Wyoming (UW) researchers in the College of Agriculture Department of Plant Sciences recently announced the results of on-site trap crop testing at four Wyoming sugar beet farms.  Trap crop radish and mustard were used instead of fumigants to control sugarbeet nematode (SBN) infestations.

Because all growers run their operations using slightly different methods and equipment, this grant funded project was designed to assure that information gained from trap crop testing in controlled settings would work on whole fields with diverse soils and conditions.  Positive results verify that small-plot trap crops work on a variety of soils and locations throughout the state.

Cooperating sugarbeet producers worked with a team of UW Cooperative Extension Service (CES) educators and college faculty members led by Dave Koch, CES agronomy specialist and professor, to effectively establish and manage trap crop radish and mustard on their farms.  Fred Gray, College of Agriculture plant pathologist and nematologist, works closely with Koch and has been instrumental in monitoring SBN.  University Extension Educator Jim Gill, of Washakie County UW CES, monitored fields, collected data and many times acted as liaison between researchers and growers.  Simplot Soilbuilders and Holly Sugar in Worland and Torrington also were involved, in addition to several College of Agriculture students.

Sage Creek Land and Livestock

In 1997, "Adagio" radish was planted on a 49-acre filed at the Hake Farm and on a 35-acre field at the Benson Farm.  Both were air planted by Simplot with a Terragator, and the fields were planted following malt barley harvest.  According to Gill, loose straw was baled on the Hake filed and on the Benson field, and the stubble was burned prior to seeding.  Both were roller-harrowed following seeding.  The estimated cost of growing radish was $50 per acre, including the cost of 50 pounds of nitrogen per acre.

Radish stands and growth were excellent on both fields.  The Hake field was plowed down and the Benson field was grazed with lambs before fall plowing.  According to John Snyder, Jr., cooperator and president of the Washakie Beet Growers Research Committee, Basin growers have been concerned with the need for fall tillage.  As a result, these two fields were the last ones plowed in mid-November.  Snyder believed that since only a few fields would be seeded with trap crops each year, there would not be a problem with fall field preparation.

Sugarbeets were planted on these same fields in 1998.  Snyder, his farming partner Con Lass and other growers in the region all remarked that the two fields appeared more uniform than in the past.  One grower noted that the combination of later planting, light soil and a warm summer usually means more significant SBN damage; however, the beets looked vigorous throughout the filed in 1998.

Sugarbeet yields in 1998 were 27.1 and 27.9 tons per acre on the Hake and Benson fields respectively.  Both were by far the highest yields ever on these fields.  Economically, these fields have generated excitement-22 tons of extra beets at $40 or more per ton, with approximately half the cost of previous nematode controls.

McKamey Farms

Cooperators Dave and Dick McKamey have always been considered progressive by other farmers in the Big Horn Basin area.  In 1997, they planted radish on a 95-acre field infested with SBN.  Even though the nematode population was knocked down considerably after that year, the brothers decided to delay sugarbeet seeding on the field until 1999.  The radish field was grazed with 2,500 lambs for 30 days.

Encouraged by the results of the previous year, the McKameys seeded two other fields with radish in 1998.  A 55-acre field was sprinkler irrigated, and a 5-acre field was furrow irrigated.  Radishes were planted late because barley maturity was later than usual that year.  The fall was exceptionally mild, and the radishes grew until mid-November, when they were grazed with Timberline lambs.  No herbicide was used on the crop and there were very few weeds.  McKamey Farms sold the radish for $70 per acre, more than enough to offset the cost of growing them.

In previous grazing studies, lambs have gained as mush as 250 pounds per acre.  At $.65 per pound for lamb, that equals $162 gross per acre.  Although cost of grazing needs to be considered, this is an excellent value-added opportunity.  According to researchers, grazing after late October does not affect SBN reduction or sugarbeet yield response for the next year.

Hort Farms

In April of 1997, cooperator Rod Hort planted a 17-acre filed with "Adagio" radish, which was grown as the sole crop for the season.  The stand was excellent, and although no herbicides were used, very few weeds emerged.  Because radish roots can easily reach three to four feet, fertilizer was not applied on this field, as Hort felt there was ample nitrogen at least three feet.

Hort hayed the first radish growth in late June and the second in early October.  Production was estimated at three and two tons per acre for the first and second harvests, respectively.  Crude protein content was 16 to 18 percent on a dry matter basis, slightly lower than alfalfa; however, fiber content was equivalent to that of high-quality alfalfa.  Acid-detergent fiber (ADF) was 30 to 34 percent, and neutral-detergent fiber (NDF) was 34 to 38 percent.  (The standard for high-quality alfalfa is 20, 30, and 40 percent crude protein, ADF and NDF, respectively.)  The potassium nitrate content, 1.1 percent, was borderline for this feed to be used as the sole forage in a diet.

Although the cattle reportedly ate radish hay in preference to alfalfa, a feeding trial has not been conducted.  The interest in feeding value of trap crop radish will be addressed in a 1999-2000 on-site study with Barry Wilhelm, a farmer near Wheatland.

The Hort field was monitored from fall 1997 to spring 1998.  Radishes reduced the SBN population by 67 percent in 1997.  The SBN population did not increase from sugar beet planting until mid-July 1998.  It was only from mid-season until sugar beet harvest that the count increased.  The initial reduction in nematode populations allowed the beets to become established and limited the damage as nematode populations increased later in the season.  Sugarbeet yield on this field was 23.8 tons per acre, higher than previous years.  This field will be studied again in 1999 and 2000.  The next crop of sugarbeets is planned in 2000.  At the last beet harvest, the SBN population was 8.9 eggs per cubic centimeter (cc) of soil.  Even with fumigant, it is not unusual for counts to be as high as 30 to 50 eggs per cc of soil at beet harvest.  Koch predicts with the three-year rotation on this field and natural mortality, the SBN will be below two eggs per cc by the next beet planting, a population below the economic threshold.  This would mean a trap crop would not be necessary for every beet crop.

For more information, contact your local Wyoming Cooperative Extension Service office or the College of Agriculture Resource Center at (307)766-2115.  Bulletins and fact sheets are available on the following topics: trap crops; designing, conducting and evaluating on farm tests; best management practices for establishment and effective use of trap crops; and soil sampling for nematode analysis.