Integrating nemade-resistant crops into sugar beet rotations

Final Report for SW97-018

Project Type: Research and Education
Funds awarded in 1997: $113,184.00
Projected End Date: 12/31/2002
Matching Federal Funds: $113.18
Region: Western
State: Wyoming
Principal Investigator:
David Koch
University of Wyoming
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Project Information

Abstract:

A whole-farm economic analysis in the Big Horn Basin, in which research results were incorporated, showed that by substituting trap crops in the rotation in lieu of nematicides, rate of return could be increased from 3.9 to 5.8% if trap crops were grown as green manure and to 9.5% if trap crops were grazed. In southeastern Wyoming, where different rotations are practiced, whole-farm analysis showed that use of trap crops in lieu of nematicides increased rate of return from 2.5 to as high as 6.3%. Both analyses decreased downside risk. Growing trap crops is less expensive than applying either of the nematicides commonly used and are safer to applicators and others, and are more environmentally friendly. Trap crops can reduce reliance on nematicides and help sustain the historically most profitable crop in the Rocky Mountain region, which generates at least $5 value-added income in processed products for every dollar of farm gate sales.

Project Objectives:

1. Determine effectiveness of SBN-resistant trap crops in reducing SBN populations and nematicide use in several alternative sugar beet rotations and with several establishment methods.
2. Determine yield effect, cost and returns of alternative rotations in which trap crops are used in lieu of nematicides.
3. Develop an educational program to demonstrate benefits of trap crops and to encourage adoption of their use by sugar beet producers.

Introduction:

Sugar beets (Beta vulgaris) are grown on 180,000 acres in the Eastern Rocky Mountain region and represent more than $120 million in annual income. Total variable costs to grow the crop are $500/acre or more, nearly half of which is spent on pest control (Hewlett and Bastian, 1992). Sugar beets have been Wyoming's most profitable crop, in spite of the high input costs.

The sugar beet (cyst) nematode (SBN), Heterodera schachtii, is the most damaging pest of sugar beet in Wyoming and many other areas worldwide. As much as half of the crop can be lost if this pest is not controlled. In a recent survey (Gray, in press), 96% of Washakie County (Wyoming) fields were infested, and 72% were above the estimated damage threshold of 2.8 eggs and/or juveniles cm-3 of soil (Griffin, 1981; Robb et al., 1992). In a more recent survey (Gray and Gill, 1995, unpub.), 54% of fields had only one year and 41% had two years between sugar beet crops.

Temik 15G® (aldicarb), a nematicide/insecticide, is applied to 30% of Wyoming's sugar beet acreage (Legg, et al., 1992). There is an increasing use of Telone II® (1,3-dichloropropene), a soil fumigant (biocide). Cost of aldicarb and 1,3-dichloro-propene at full-label rate is about $90 and $120-$130/acre, respectively. These nematicides are restricted-use chemicals and represent a significant environmental risk to air and water, as well as a health risk to applicators. They have been found in ground and surface water in several states (Roberts and Thomason, 1981). Future availability of these materials is uncertain.

Sustainability of the sugar beet industry is threatened by the continued use of nematicides. In spite of increased use of nematicides, soil populations of the SBN are still relatively high. In some areas there has been a decreased acreage of sugar beets due to buildup of pests. This has resulted in poor yields and quality of beets, increased inputs and the need to grow sugar beets more remotely from the factory, with an increased cost due to transportation.

Sugar beets are intensively grown in Wyoming. For the most part, legume, green manure or cover crops have not been utilized. Extensive tillage, use of heavy equipment and many trips over the field have led to such problems as soil compaction, reduction in tilth, depletion of organic matter and greater likelihood of leaching of soluble nutrients and pesticide residues. The results of the proposed research would contribute information to these areas of concern.

The increase in "flex" acres proposed in the 1995 Farm Bill provides an opportunity to try new and alternate crops without penalty. There will likely be encouragement for the concepts of sustainability, integrated pest management and conservation of natural resources.

In Germany and the Netherlands the nematicides that control SBN have been removed from the market due to ground water contamination. SBN-resistant radish and mustard, which act to "trap" and prevent SBN reproduction and effectively reduce soil populations have been developed and used successfully.

At grower meetings, there has been considerable interest in the recent findings of work in Wyoming, which show the potential for reduced nematicide use and fall grazing of trap crop radish following malt barley. Growers, however, have suggested that more work be done on modifying other rotations to accommodate the use of trap crops. They further request that alternatives methods for establishing trap crops, which will facilitate their planting at a very busy time, be evaluated.

The SBN occurs throughout the sugar beet-growing areas in the western U.S.(Christie, 1959). Continuous feeding by large numbers of nematodes and the release of a toxin into sugar beet roots results in stunted plants. High soil populations of SBN may result in poor emergence and poor stands (Stelle, 1989).

Relative to control, crops are categorized as either susceptible (soil population of SBN is increased), neutral (population unaffected) or resistant (population of reduced) (Roberts and Thomason, 1981). Crops susceptible to SBN include sugar beet and table beet, radish (Raphanus sativa), most Brassica crops and weeds, including mustards. Neutral plants include small grains, pea, dry bean, corn, grasses and alfalfa (Medicago sativa). Resistant plants include the recently developed radish and mustard trap crop cultivars (Spittel, 1986).

The resistance mechanism of these cultivars is as follows: (1) root exudates stimulate eggs within cysts (dead females of H. schachtii) to hatch, releasing infective juveniles, as occurs with susceptible plants; (2) infective juveniles are attracted by exudates and infect roots, as with susceptible plants; (3) development of juveniles into adult females is inhibited and nematodes starve, while reproductive cycles are completed in roots of susceptible plants (Christie, 1959 and Spittel, 1986). Gardner and Caswell-Chen, 1993, in the U.S., reported the effectiveness of nematode trapping.

The SBN has been controlled by crop rotations, nematicides and, more recently, by trap crops. Resistant sugar beet cultivars would be the ideal control, however, agronomically- desirable SBN-resistant cultivars are not available (Lange and De Bock, 1994). The time required to reduce the soil population below the damage threshold level with non-host crops depends on the initial soil population of SBN (Gray, et al., 1992). In Utah, a 6-year sugar beet rotation resulted in holding SBN populations below the damage threshold (G.D. Griffin, pers. comm.), avoiding the need for nematicides. The common rotations in Wyoming, sugar beet-corn-dry bean and sugar beet-malt barley, are too short for adequate control of even moderate soil populations of SBN. Lengthening rotations may not be economically practical due to the high value and potential profitability of the sugar beet crop and the lack of adapted and profitable cash crops for Wyoming's climate (Koch, et al., 1995). However, modifying the rotation with alternative crops has merit, as it would allow the advantageous use of trap crops.

A recent analysis, based on yields the past five years shows that with average prices, the gross margin for wheat and corn are about the same. The current high price of wheat provides an opportunity to substitute wheat for corn. In addition to providing more growth of trap crops following main crop harvest, other advantages of wheat are: (1) providing a winter cover, particularly important on coarse-textured soils; (2) better control of weeds and other pests affecting the summer annual crops in the rotation; (3) reduced cost of production, compared to corn, dry beans and sugar beets; (4) spreading of the seasonal farm workload; and (5) greater diversification of cash cropping.

Although there is little information on price and cost of production for pea/oat (Pisum sativum/Avena sativa) forage mix, these species are well adapted to Wyoming growing conditions. Three to 3 1/2 tons/acre of high-quality hay are regularly obtained with this mixture. The pea in the mixture increases dry matter and protein content over straight oats (Green et al., 1995). This crop offers similar advantages as winter wheat in a sugar beet rotation, except that it is spring-planted. It may be more appealing than winter wheat to crop-livestock producers.

Varieties of fodder radish (Raphanus sativa) and yellow mustard (Sinapsis alba), selected for resistance to SBN (trap crops) and their ability to reduce SBN populations, are a promising alternative to nematicides. Technology for substituting trap crop use for nematicides was first developed in Europe (Peterson, 1992). Trap crops are an integral part of European sugar beet production. However, there is a need to determine the best way to utilize trap crops in the U.S. where climate, soils, irrigation, rotations and management of sugar beets differ. Planting full-season trap crops, an area of current research in Germany and Holland, would maximize their ability to cleanse the soil of SBN and contribute forage and/or green manure, however, the economics may favor second-crop use. Knowing the effectiveness of full-season, compared with second-cropping, would be helpful in shaping future farm programs emphasizing integrated pest management. SBN-resistant trap crop cultivars, bred in Europe, are now available in the U.S. (Hilleshog Mono-hy, Inc.).

In Wyoming, trap crops, used as a second crop following malt barley, have reduced soil SBN populations 50-75% over a 10-week period (August to mid-October) (Gray, et al., 1994). Grazing of trap crops in the fall has produced 220 to 250 lb/A of lamb without significant effect on nematode control or sugar beet yields (Koch, et al., 1995). Sugar beet yield the following year was increased 4 to 5 tons per acre with trap crop radish and without nematicide. Cost of growing trap crops is less than the cost of the full-label rate of aldicarb or 1,3-dichloropropene.

Following dry beans and corn, the effect of trap crops on SBN control and subsequent sugar beet yield was not adequate to justify expense of growing trap crops. This is related to the much shorter time of favorable conditions following dry beans and corn harvest, compared to malt barley. These unpublished results are summarized in a final report (September 1995) to the granting agency (USDA-SARE program) and are in agreement with those of Wilson, et al. (1993) in Nebraska.

Initial tests in Wyoming show that trap crops utilize large amounts of residual soil nitrogen (N). Mid-summer plantings have produced more than 1 ton/A of low fiber dry matter. Plow down of this high-quality organic matter would be expected to alleviate some of the soil problems mentioned above. In a grazing study (unpub. data), trap crop mustard planted in late July reduced residual soil nitrates 40% in the top three feet of soil (unpub. data). Additionally, organic matter additions to the soil have been reported to stimulate activity of naturally-occurring antagonists and parasites of nematodes and other soil-borne pathogens (Stirling, 1991).

Cooperators

Click linked name(s) to expand
  • Fred Gray
  • Larry Held
  • James Krall

Research

Materials and methods:

A rotation alternative study will be established in Year 1 on nematode-infested fields with two cooperators. Rotation treatments (main plots) will include: (1) a standard rotation (dry bean, corn, sugar beet) - corn will be the initial crop; (2) the same rotation in which winter wheat is substituted for corn (dry bean, winter wheat, and sugar beet); (3) the same as no. 2, except that winter wheat will be followed by trap crop radish as a second crop (dry bean, winter wheat followed by radish, and sugar beet); (4) trap crop radish, planted as a second crop following pea/oat forage mix, which will be harvested as hay (dry bean, pea/oat mix followed by radish, and sugar beet); and (5) trap crop radishes planted as a full-season crop(dry bean,radish, and sugar beet). All plots will be seeded to sugar beet in Year 2. Experimental design will be a split-plot with five replications. Sub-plots will be aldicarb treatments at 0 and 4.5 lb/A active ingredient, applied at sugar beet planting. The study will be repeated on a different field with the same cooperators, starting in Year 2. Trap crop management practices will be based on previous studies in Wyoming (Koch, et al., 1995).

With yields and other information from the study under Objective 1, an enterprise budget, utilizing custom rates for equipment used, actual inputs of seed, irrigation water, fertilizer, pesticides, fuel, and labor required for each operation will be developed for each of the crops included in the five rotation treatments (Hewlett and Bastian, 1992, and Hewlett, et al., 1991). The effect on subsequent sugar beet yields, based on contracted price of beets will be included in the budgets. Based on yield data, additional costs of growing trap crops and substitution of trap crops for nematicides, an economic analysis will be provided on the various alternatives and rotations. This economic analysis will be facilitated by combining the enterprise budgets for individual crops into a series of total farm systems budgets corresponding to the five rotation treatments. Each rotation treatment will be evaluated in terms of average annual profitability (net return per acre) outcomes from each corresponding total farm budget. The sensitivity of profitability comparisons (between treatments) will be further tested using alternative price-yield combinations (pessimistic to optimistic) in relation to the standard (most expected) price-yield possibilities.

A trap crop establishment method study will be conducted on an SBN-infested field in Washakie County(Wayne Mosegard) and in Goshen County (Steve Faegler). Treatments, replicated three times in a randomized complete block, will consist of (1) interseeding 'Adagio' radish into barley (Mosegards) or wheat (Faeglers) prior to the last irrigation; (2) broadcasting radish following barley or wheat harvest; and (3) drilling radish into barley or wheat stubble. An air spreader (Terregator®), owned and operated by the local cooperative (J.R. Simplot) will be used for Treatment 2. On the Torrington Research and Extension (R&E) Center, a cover crop/soil conservation study will be established in 1996. The study will be repeated in 1997-98. Mustard cultivar, Metex, and radish cultivar, Adagio, will be compared in main plots with winter wheat and bare fallow in a spit-plot experiment. All will be planted as a second crop following winter wheat. Sub-plots will be either grazed with lambs in October or left ungrazed. Another study will be initiated with the purpose of determining amount of N required to produce optimum trap crop growth in order to maximize residual soil nitrate removal. A split-plot design with the above trap cultivars as main plots and residual N levels as sub-plots and four replications will be initiated. Soil nitrogen will be determined in the spring of 1997 and fertilizer N applied to winter wheat to obtain a range from low to high residual soil N at wheat harvest in July.

Yields of all crops will be determined. Soil populations of SBN will be determined at the outset, after termination of trap crop growth in the fall and at sugar beet planting the following spring. Cysts of SBN and the number of viable eggs and juveniles in cysts determined (Roberts and Thomason, 1981). Amount and nature of trap crop and wheat ground cover will be determined, fall and spring. Soil and air temperatures, soil moisture, amount of irrigation water and precipitation will be monitored. A complete soil physical and chemical analysis will be completed before and after each study. Soil nitrate levels will be determined before and after trap crop by core sampling with a Giddings Soil Sampler. Other diseases and pests of sugar beet will be noted. There will be a written agreement with cooperating growers outlining responsibilities all parties. A winter planning meeting will be scheduled each year.

The Project Coordinator will be responsible for completing work planned, preparation of progress reports and publication of results. Dr. Gray will oversee the nematode sampling and analysis and monitoring of diseases. Dr. Krall will assist with establishment of studies and collection of agronomic data. Dr. Blaylock will assist with measurement of soil parameters. Dr. Held will be responsible for the economic evaluations. Dr. Fornstrom will assist in cover crop and rotation studies and in collecting environmental data. Mr. Baumgartner (NRCS) will cooperate in planning and conducting Field Days. Mr. Synder will assist in planting the establishment studies. Cooperators will maintain records on production inputs and provide equipment. County Agents will assist in studies and plan grower meetings.

Research results and discussion:

Trap crops (radish and mustard) were grown in six rotations, compared with two traditional rotation crops, corn and wheat, on two producer fields in 1998-99 (Lapp Farm, L98) and (Shield Farm, S98) and one location in 1999-2000 (Shield Farm, S99) in Southeast Wyoming. All rotations at all three sites were replicated and on all sites sugar beets were grown the second year.

Spring-planted radish and mustard produced between 2 and 5 tons/acre of dry matter by mid-summer, when they were mowed to prevent seed production. Except at one site in which trap crops were mowed to 2 inches, all recovered and produced significant amounts of growth by fall, when they were incorporated as green manure. Second-crop radish and mustard produced 1.5 to 5 tons/acre.

Initial soil populations of the sugar beet nematode (SBN) were 3.0, 8.7 and 29 eggs/cc of soil on the L98, S98 and S99 fields, respectively. In 1998 at the L98 and S98 sites, an average 14% reduction in SBN occurred during corn and wheat production. This is considered a natural reduction in SBN because these are both neutral crops. Greatest SBN reduction, 48-55%, occurred in the wheat, followed by second-crop radish or mustard. Pea-oat forage, followed by radish or mustard, reduced SBN 27-49% and full-season radish and mustard reduced SBN 14-43%. In 1999 at the S99 site, SBN reduction with corn and wheat was 57 and 59%. Reduction in SBN with full season trap crops, trap crops planted after wheat, and trap crops planted after pea-oat harvest was 64, 62, and 60%, respectively. Over the three locations and two years, SBN reduction following neutral crops was 32%, while SBN reduction following full-season trap crops, trap crops following pea-oat and trap crops following wheat was 40, 45, and 55%, respectively. In late fall, SBN populations at the L98 site were below the estimated economic threshold of 4.5 eggs/cc of soil for all rotational treatments (average 1.75 eggs/cc). At the S98 site, SBN populations were all still above the economic threshold (average 6.1 eggs/cc). At the S99 site, SBN populations were still high, averaging 12.9 for corn and wheat and 10.6 for rotational treatments involving trap crops.

Overall sugar beet yields were low on the L98 and S98 fields due to poor stands, high weed pressure and problems with irrigation. As a result, there were small differences as a result of rotational crops the previous year. At the L98 site, sugar beet yield in 1999 averaged 13.6 tons/acre on plots growing corn and wheat the previous year, while sugar beet yield averaged 12.7 tons/acre on plots which had trap crops. At the S98 site, sugar beet yield averaged 6.9 tons/acre on plots previously growing corn and wheat and 7.4 tons/acre where trap crops had been grown. On the S99 field, sugar beet yield was 17.2 tons/acre following corn and wheat and 18.8 tons/acre following rotational treatments including trap crops. Yield in 2000 was greatest (19.4 tons/acre) where sugar beets followed the 1998 rotation in which wheat and pea-oat was followed by second-crop radish and mustard.

A multimedia approach was used to disseminate information regarding the use of trap crops. We presented results of our research at the Western SARE Conference in Portland. Our project was one of 12 from across the country to be featured in SARE 2000 Highlights. Two news releases and at least 10 popular articles were published in sugar beet producer journals, other farm journals and in newspapers, including an article on the front page of the Wall Street Journal. Trap crop information was posted on the Holly Sugar Website to all contracted beet growers. A bulletin on the design, conduct and evaluation of on-farm tests was published. We made four extension presentations and took part in three field days, one sponsored by Holly Sugar Company and one as part of an Integrated Pest Management tour. Also, we consulted numerous times with our cooperating producers in the course of conducting studies on their fields.

Research conclusions:

Growing trap crops for control of the SBN provides the producer an opportunity to reduce pesticide use as well as reduce cost of production. Additionally, there is a strong suggestion from research to date that sugar beet yields are improved through a rotation effect.

The pesticides used for SBN control are aldicarb (Temik) and 1,3-dichloropropene (Telone II), both of which have been found in ground and/or surface water in several states. Both are currently under special government review. Cost for the full-label rate of aldicarb and 1,3-dichloropropene is $110 and $200/acre, respectively.

The SBN is the most damaging pest of sugar beet in Wyoming, as in most sugar beet-growing areas worldwide. In a recent survey in Wyoming, for example, 72% of fields were above the estimated economic damage threshold. Temik has been applied on over 30% of sugar beet acreage in Wyoming. Telone is being used on increasing acreage in an effort to maintain short rotations because sugar beets are, in spite of high input costs, the most profitable crop. The value of sugar is likely to be maintained because there is a growing world demand. Total variable costs to grow the crop are $500/acre or more, most of which is for disease and pest control.

Sugar beets are grown on more than 250,000 acres in the Eastern Rocky Mountain region and represent more than $950 million in annual income. In Wyoming alone the value-added by the sugar industry is about $5 for every dollar of sugar beets produced. In other words, the $50 million, on average, of sugar beet receipts in Wyoming each year generates, through processing, over $250 million of economic activity. Loss of the pesticides that control the sugar beet nematode, without a replacement control method, would have a catastrophic impact on agriculture in the region.

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

Book Chapter:

Gray, F.A. and D.W. Koch. In press. Trap Crops. In Cultural Practices, Encyclopedia of Pest Management. Marcel Dekker, N.Y.

Thesis:

Geving, E.B. 2000. Economics of trap crop radish for control of sugarbeet nematodes in southeast Wyoming. University of Wyoming, 97 pp.

Scientific articles:

Held, L.J., J.W. Jennings, D.W. Koch and F.A. Gray. 2000. Economics of trap cropping for sugar beet nematode control. J. Sugar Beet Research 37:45-55.

Krall, J.M., D.W. Koch, F.A. Gray and J. Nachtman. 2000. Cultural management of trap crops for control of sugar beet nematode. J. Sugar Beet Research 37:27-43.

Held, L.J., J.W. Jennings, D.W. Koch and F.A. Gray. 2000. Trap crop radish: a sustainable alternative for nematicide in sugar beets. J. Amer. Soc. Farm Managers and Rural Appraisers 63:118-126.

Held, L.J., J.W. Jennings, D.W. Koch and F.A. Gray. 1999. Trap crop radish: A sustainable alternative for nematicide in sugar beets. J. Agric. and Resource Economics 24(2):589.

Professional presentations:

Koch, D.W., F.A. Gray, J.M. Krall and J.W. Flake. 2001. Trap cropping for sugarbeet nematode control in southeastern Wyoming. Proc. 31st Biennial Meeting, Amer. Sugar Beet Technologists, Vancouver, Canada.

Geving, E.B., L.J. Held, D.W. Koch, F.A. Gray and T.K. Foulke. 2000. Economics of integrating trap corp radish in crop rotations for sugar beet cyst nematode control in southeastern Wyoming. W. Soc. Crop Science Abstract (in press). Moscow, ID.

Gould, J., E. Scholljegerdes, B. Hess, D.W. Koch, J.W. Flake, and L.J. Held. 2000. Replacement value of radish hay for alfalfa hay in diets of newly-weaned beef calves. W. Amer. Soc. Anim. Sci Abstract (in press).

Gray, FA. and D.W. Koch. 2000. Trap cropping for sugar beet nematode control: economic viability. W. SARE Conference, Portland, OR.

Popular articles published:

"Trap crops prevent worms from multiplying and harming a cash crop." The Wall Street Journal Vol. CCXXXVI, No. 8, p. 1, July 13, 2000.

"Publication highlights trap-crop research." July/August 2000. The Sugar Producer Magazine, p. 28 (circulation to the vast majority of sugar beet growers in the U.S.).

"Using trap crops for sugar beet nematode control." Spring 2000 Annual Sugar Beet Edition.
The Business Farmer, Scottsbluff, NE and Torrington Telegraph.

"Beet nematode research shown at Holly Field Day," August 2000. The Business Farmer, Scottsbluff, NE.

"UW professor featured in national publication," August 2000. Laramie Boomerang.

"Wyoming researchers report success in nematode control with trap crops." August 2000. Western Farm Press.

"Wyoming research touted," August 2000. W. Farmer-Stockman.

Koch, D.W. April 2000. Crops for extending the grazing season. Wyoming Livestock Roundup.

"UW trap crop research receives national recognition. August 2000. College of Agriculture Agademics.

"Novel rotation blocks nematode damage in sugar beets. Sustainable Agriculture Research and Education Program 2000 Highlights, p. 3 (one of 12 projects selected from throughout the country).

Bulletins published:

Koch, D.W. and J.W. Flake. In press. Designing, conducting and evaluating on-farm/ranch tests. Wyoming Coop. Ext. Serv. Bul.

The above bulletin is available at Http://www.uwyo.edu/ag/ces/plantsci.htm

News releases:
"UW trap crop research is featured in SARE 2000 Highlights." UW College of Agriculture Press Release, June 12, 2000.

"UW investigators recognized nationally for research on sugar beet nematode control, September 2000. University of Wyoming Press Release.

Extension presentations:

"Advances in management of the sugarbeeet cyst nematode." Jan. 2001. Proc. Montana/Wyoming Sgarbeet Symposium, Billings, MT.

"Control of sugar beet nematode. Aug. 2001. Holly Sugar Tour, Torrington, WY.

"Trap crops in an integrated pest management program for controlling the sugar beet nematode." July 2000. Archer Research and Extension (R&E) Center Field Tour.

"Trap crop use in sugar beet rotations." July 2000. Torrington R&E Center Field Day.

"Trap crop use in sugar beet rotations." August 2000. Holly Sugar Corporation Field Tour.

Project Outcomes

Project outcomes:

The economics of substituting trap crop production for nematicides in commonly- grown, as well as alternative, rotations in southeastern Wyoming was studied. Revenues, costs, and net returns to real estate for six 3-year rotations were determined. The standard practice of growing sugar beets with use of nematicide following dry beans and corn resulted in an average rate of return of 2.48%. Rotations with second-crop radish had the highest rates of return with the rotation of beets-dry beans-winter wheat followed by radish yielding 6.29% and the rotation of beets-dry beans-malting barley followed by radish resulting in 5.75% return. Also more profitable than the standard beets-beans-corn rotation with nematicide was the rotation of beets-beans-full season radish, which produced 4.80% return. Less profitable than the standard rotation with nematicide were beets-malting barley followed by second-crop radish-corn, which produced 2.77% return and the beets-corn-full-season radish rotation, which produced 1.82% return. Downside risk was determined for each rotation. Lowest risk was with the most profitable rotation, beets-dry beans-winter wheat followed with second-crop radish. Net returns fell below $0 two of 15 years, while the standard beets-beans-corn rotation using nematicide fell below $0 seven of 15 years.

Extending the rotation length will reduce the need for nematicide; however, including second-crop radish in four-year rotations was found to be profitable, although the differences were less than with 3-year rotations. Adding second-crop radish to a beets-corn-beans-wheat rotation increased returns from 3.02 to 3.93%. Adding second-crop radish to a beets-beans-corn-barley rotation increased returns from 2.94% to 3.53%. Cost savings from soil fumigation elimination is the largest contributing factor to higher rates of return for rotations including trap crops. Adopting the practice of using trap crops for SBN control and adding a small grain of winter wheat or malting barley is expected to increase profitability and reduce risk, thus improving sustainability of sugar beet production in southeastern Wyoming and similar growing areas.

Farmer Adoption

Trap crop varieties of radish have been commercially available for five years. In the third year in which seed was available to producers sales in Wyoming, Montana, Colorado and Nebraska were 14,200 lb of seed. Based on recommended seeding rate, over 640 acres of trap crop were planted. This information is courtesy of Hilleshog Mono Hi, who no longer sell trap crop seed. Some disruption in seed availability has occurred as a result of a change in seed distributors. Originally, all trap crop had to be imported. Recently, another company in Oregon with their own varieties has marketed trap crop seed. American Crystal Company now markets trap crop seed. They have indicated that they have back ordered seed twice as a result of very heavy demand in 2001. As yet, we have not gotten a report on 2001 seed sales. A number of producers in Wyoming have indicated that they would have planted trap crop radish in 2000 and in 2001 if seed had been available. Several producers with which we have worked in the pursuit of grant objectives have planted trap crops for at least three years. At this point, it seems that trap crop adoption is limited more by availability of seed and the turmoil in the sugar industry than by awareness of the benefits of the use of trap crops.

Recommendations:

Areas needing additional study

More research is needed to study the effect of trap crops on other crops in the rotation. Studies to date have focused on effects on the sugar beet crop. Since organic matter is added to the soil as a result of green manure and/or livestock manure, there is expected to be a positive impact on yield of succeeding crops. Also, there may be reduced need for fertilizer in the future. Livestock grazing was entirely with sheep; therefore, there is a need to evaluate the utilization and economics of trap crops with cattle. Also, there is a need to study the long-term effect of growing trap crops, that is, whether they need to be grown in every sugar beet rotation.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.