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Krall, J.M., D.W. Koch, F.A. Gray, and L.M. Yun. 1996. Potential of sugar beet nematode-resistant radishes and mustard for use in sugar beet rotations. p. 619-622. In: J. Janick (ed.), Progress in new crops. ASHS Press, Arlington, VA.

Potential of Sugar Beet Nematode-Resistant Radishes and Mustard for Use in Sugar Beet Rotations

James M. Krall, David W. Koch, Fred A. Gray, and Li Mei Yun

  1. METHODOLOGY
  2. RESULTS
  3. REFERENCES
  4. Table 1
  5. Table 2
  6. Table 3
Current production of sugar beet (Beta vulgaris L.) relies on extensive use of pesticides. Annual losses from pests in the Western United States are greater than 25% (Roberts and Thomason 1981). In Wyoming, 65% of fields in long-term sugar beet production are infested with the sugar beet (cyst) nematode (SBN), Hederodera schachtii Schmidt (F.A. Gray pers. commun.). In Wyoming, aldicarb is applied to 30% of sugar beet hectarage and an increasing hectarage is treated with the pre-plant soil fumigant 1,3-dichloropropene (Legg et al. 1992). Continued use of nematicides threatens the sustained production of sugar beets because of their high cost and environmental risks.

Agronomically-desirable nematode-resistant sugar beet cultivars are unavailable. In Wyoming and other areas sugar beets are grown in two- or three-year rotations. Longer rotations, which would help in the control of SBN, are not economically practical due to lack of adapted and profitable crops. SBN-resistant "trap crop" varieties are available and their use is currently a major control practice in Europe (Peterson 1992). Seed of nematode-resistant radish (Raphanus sativus L.) and mustard (Sinapsis alba L.) has recently become available in the United States. Technology for using these cultivars in United States sugar beet rotations has not been adequately developed. In western Nebraska, trap crop cultivars grew best when planted between mid-May and mid-Aug., when soil temperatures at 15 cm were above 20°C (Wilson et al. 1993). A major limitation of this method is the limited amount of time and growing degree days following harvest of the main crop. Full-season production is probably not justified economically as a routine practice. The objectives of this study were to determine the potential for biological control of SBN with SBN-resistant cultivars and the potential for utilizing these crops for fall grazing.

METHODOLOGY

A cooperating farmer's (Hefenieder) field on which the SBN had been a problem was selected for initiating a test in 1992. Following malt barley (Hordeum vulgare L.) harvest in 1992, straw was baled and removed and the field was tilled twice with a tandem disk. 'Pegletta' radish was planted with a disk drill at 24 kg ha-1 on July 28. The experimental design was a split-plot with six replications. Main plots (1992) were radish-seeded as a second crop or unseeded (normal fallow). Subplots (at sugar beet planting in 1993) were aldicarb rates of 0, 2.5 or 5.0 kg ha-1 a.i. The latter rates represent one-half and full-label rates of aldicarb, applied as Temikreg. 15G. Main plots were 12 by 12 m and subplots were 4 by 12 m. Ammonium nitrate was surface-applied at 56 kg ha-1 at time of radish planting. Plots were furrow-irrigated twice during radish growth.

Another cooperator's field (Mosegard) was used to study the effect of grazing the SBN-resistant radish cultivar, `Adagio', on SBN control. Malt barley was harvested Aug. 2, 1994. The field was burned and on Aug. 4, seed (22 kg ha-1) was mixed with fertilizer (67 kg ha-1 N as ammonium nitrate) and applied with a spinner-broadcast type applicator. Replicated strips were left unseeded. The field was roller-harrowed to cover the seed and firm the seedbed. The field was furrow-irrigated twice. Sethoxydim at 0.31 kg ha-1 a.i. and oil concentrate at 2.3 l ha-1 was applied for the control of volunteer barley on Aug. 27, when barley was about 10 cm in height. The experimental design was a randomized complete block with five replications. Treatments were: (1) unseeded and ungrazed; (2) radish-seeded and fall-grazed; and (3) radish-seeded and fall growth plowed down, rather than grazed. Following evaluation of radish stand and growth, 150 lambs averaging 33.1 kg grazed on 1.8 ha from Oct. 13 until Nov. 12. Lambs were weighed to determine daily weight gain and gain ha-1. Following grazing the entire field was moldboard plowed. Sugar beets were planted on the entire field in 1995 with no nematicides applied to the study area and sugar beet yields and quality components were evaluated.

On the above two test sites, populations of SBN were determined before and after the radish crop, at sugar beet planting, at mid-season and at sugar beet harvesting. Two hundred cm3 of soil was processed through an elutriator and cysts, eggs, and juveniles counted. SBN counts were adjusted for efficiency of extraction and nematode population data were subjected to covariance analysis.

Trap crop mustard was evaluated for grazing potential at the Torrington Research and Extension Center, where there are no SBN. In 1993, following harvest of feed barley, loose straw was removed and `Metex' mustard was planted on Aug. 16 at 21 kg ha-1 with a disk drill into stubble averaging 20 cm in height. Soil analysis showed low phosphorus, therefore, 72 kg N and 93 kg P ha-1 were applied. The field was divided into three seeded blocks (0.15 ha each) and three unseeded blocks (0.05 ha each). Lambs grazed 0.11 ha of each seeded block. Eight lambs grazed each block from Oct. 29 until Nov. 12 and weight gain was determined. The entire field was spring-plowed and uniformly planted to sugar beets in 1994.

In 1994 the same grazing study was repeated on a different field of the Torrington R & E following winter wheat (Triticum aestivum L. emend. Thell) harvest. The methods were the same, except that phosporus fertility was higher and no phosphorus fertilizer was applied. Planting date was on July 26 and plots were grazed Nov. 4 to 14.

RESULTS

SBN-resistant radish cultivars, 'Pegletta' and 'Adagio', planted as a second crop following malt barley reduced soil populations of SBN 54% and 71% over a 2 1/2-month period (Table 1). The greater reduction on the Mosegard field, compared with the Hefenieder field, may have been related to better soil moisture and the greater amount of plant growth. Radishes at Hefenieders appeared to have been overwatered.

On the Hefenieder field SBN populations at sugar beet planting in April 1993 were below the estimated damage threshold (EDT = 2.8 eggs and/or juveniles cm-3) (Griffin 1981) (Table 2). SBN population remained lower than with the unseeded fallow treatment throughout the sugar beet season. At mid-season (July) the SBN population was 26% lower for radish-seeded, compared to conventional fallow plots. At sugar beet harvest in Sept. the SBN population was significantly (25%) lower for radish-seeded compared to unseeded plots. Aldicarb, band-applied along the seed row at sugar beet planting, did not significantly reduce SBN population, even at the full-label rate. While aldicarb application did not increase sugar beet yield, radish inclusion in the rotation the previous year increased sugar beet yield 8.78 Mg ha-1. Estimated cost of growing SBN-resistant mustard and radish is $192 and $206 ha-1. The yield increase with radishes on this field was well above the estimated 4.9 Mg ha-1 needed to offset the cost of growing radishes, based on the average price of sugar beets, $45.83 Mg-1, over the past five years.

Both trap-crop cultivars are high in forage quality and are readily consumed by lambs (Table 3). 'Metex' mustard is capable of high yields of topgrowth, as evidenced by the 1994 planting at the Torrington Research and Extension Center. Performance (average daily gain) was greater with mustard than with radish. Gains on mustard were nearly comparable to gains on hay and grain diets. With all three grazing studies the value of lamb produced ha-1 was greater than the cost of growing the crops. On the Mosegard field there was no difference in SBN populations with grazing vs plowdown of radishes. Radishes were not grazed until growth had stopped and soil temperatures were too low for SBN activity.

REFERENCES

Table 1. Top growth and sugar beet nematode (SBN) reduction with SBN-resistant radish and mustard cultivars.

Location/year Preceeding crop Trap crop planted Planting date Top growth (Mg/ha) Growing degree days (base 4.4°C) SBN reductionz (%)
Hefenieder/1992 Malt barley Pegletta radish July 28 1.56 1758 54
Mosegard/1994 Malt barley Adagio radish Aug. 4 2.52 1658 71
Torr. R&Ey/1993 Feed barley Metex mustard Aug. 12 1.90 1279 --
Torr. R&E/1994 Winter wheat Metex mustard July 26 8.56 2168 --
zFrom the time when trap crop was planted until plow down in the fall.
yFields at the Torrington Research and Extension Center are not infested with SBN.

Table 2. Effect of 'Pegletta' radish (grown as a second crop in 1992) and aldicarb on SBN population and sugar beet yields in 1993 (Hefenieder field).

Sugar beet nematode population
(No. eggs and/or juveniles cm-3 of soil)
Treatment Aug. 1992 Oct. 1992 Apr. 1993 July 1993 Sept. 1993 Sugar beet yield (Mg/ha)
Radish effect
Unseeded (fallow) 2.04 az 1.93 a 2.55 a 4.66 a 6.83 a 31.72 b
Radish seeded 2.90 a 1.33 a 2.48 a 3.43 a 5.10 b 40.50 a
Nematicide effecty
Untreated (no aldicarb) -- -- 2.33 a 4.33 a 6.19 a 37.78 a
Half rate of aldicarb -- -- 2.78 a 4.30 a 5.39 a 35.16 a
Full rate of aldicarb -- -- 2.44 a 3.52 a 6.66 a 35.38 a
Interaction -- -- n.s. n.s. n.s. n.s.
zMeans followed by different letter within columns are significantly different at the
P <0.05 level.
yHalf-label and full-label rate of aldicarb, 2.5 and 5.0 kg ha-1, applied at sugar beet planting in Apr. 1993.

Table 3. Forage production, quality and performance of lambs grazing SBN-resistant radishes and mustard.

Forage yield (Mg/ha)
Cooperator/
Location		 Crop Totalz Trap crop Crude protein (g/kg) Utilization (g/kg) ADGy (kg) Lamb gain/ha (kg) Value of lambx ($/ha)
Mosegard Radish 3.00 2.52 154 740 0.169 251 319
Torr. R&E
 1993 Mustard 2.63 1.90 129 870 0.309 308 393
 1994 Mustard 8.74 8.56 126 460 0.336 1230 709
zIncludes volunteer grain.
yAverage daily gain.
xBased on average Oct. lamb price ($1.25/kg) for the past five years.

Last update July 1, 1997 aw