The objective of the study was to determine the effect of different weed management treatments on the stand of wild radish (one of the species that dominated the weed spectrum in the experiment vineyard) over the medium term.

 

Introduction

Wild radish (Raphanus raphanistrum L.) is commonly found in the vineyards of the Western Cape. This erect weed (Figure 1a) grows mainly during winter and early spring and can reach a height of 90 cm. The leaves form a large basal rosette, while those on the stems are situated alternately. The leaves have a bigger lobe at the end of the leaf, with the smaller lobes positioned alternately (Figure 1b). The corolla of the flower is normally yellow, but can also be white or purple. The fruit is cylindrical, constricted between the seeds and end in an acute beak.

 

FIGURE 1. The (a) upright habitus and

(b) leaves, flowers and seeds of wild radish (Raphanus raphanistrum).

 

Materials and methods

Twelve treatments (Table 1) were applied from April 2009 to August 2014 in a full-bearing, seven-year-old drip irrigated Shiraz/101-14 Mgt vineyard established on a sandy to sandy clay loam soil (33°58’S, 18°50’E) near Stellenbosch. Five cover crop species and a treatment in which no winter growing cover crop was established (weeds) were evaluated. Two management practices were applied to each of the six winter treatments during grapevine bud break, as fully described in Part 1 of the series. One consisted of full surface, post-emergence weed control applied early September with 1.8 kg/ha glyphosate (CC) and the other consisted of cover crops/weeds slashed and immediately thereafter incorporated to a depth of 200 mm with a disc harrow (MC) during the same period. In the last-mentioned practice, 0.6 kg/ha glyphosate was applied to the vine row. In both practices, 1.8 kg/ha glyphosate was applied full surface during the first week of December. During May 2012, 1 kg/ha of fluasifop-butyl was applied full surface to all treatments, except the two Pallinup oats (Avena sativa cv. Pallinup) treatments. The cover crops were established and the dry matter production (DMP) of wild radish was determined, as fully described in Part 1 of the series.

 

 

Results and discussions

As expected, no wild radish occurred in the April evaluations. Therefore, the following discussions focus on the August and November evaluations.

 

Weeds, CC and MC

The stand of wild radish was, with the exception of August 2010, 2011 and 2012, lower in the CC treatment than in the MC treatment (Figure 2a). This difference was significant in August 2011, November 2011 and November 2012. The CC treatment achieved total control in November 2012 only, with nearly a 100% control achieved in November 2011. This effective control of wild radish must have reduced the seedbed over time, resulting in the poor stand observed in August 2013.

 

Pallinup oats, CC and MC

Pallinup oats (CC) controlled wild radish totally in November 2012, the fourth grapevine growing season of the trial (Figure 2b). The stand of wild radish in the CC and MC treatments tended to be higher in August 2013 than in August 2009. This is an indication that the seedbed could not be reduced. The wild radish stand in the CC treatment tended to be lower than that of the MC treatment throughout the study. In November 2010, August 2011, November 2011, August 2012 and August 2013 this difference was significant. This supports the trend observed for the two weeds treatments (Figure 2a).

 

White mustard (Sinapis alba cv. Braco), CC and MC

Wild radish appeared for the first time in white mustard (CC) in November 2009. White mustard (CC) suppressed wild radish totally during November 2011 and November 2012 (Figure 2c). The stand of wild radish in the white mustard (CC) treatment at the end of winter (August) declined from August 2011 to August 2013. The effective control of wild radish during November must have reduced the seedbed in this treatment over time, resulting in the declining stand during winter. White mustard (MC) gave total control of wild radish during 2012.

The wild radish stand in the white mustard treatments (Figure 2c) during 2010 (least significant difference (LSD) August 2010 = 4.20, LSD November 2010 = 0.94), as well as in August 2012 (LSD = 7.11), was significantly lower than that of the stand in the weeds treatments (Figure 2a). This is an indication that the use of white mustard as a winter cover crop may improve the control of wild radish.

 

Canola (Brassica napus cv. AVJade), CC and MC

Canola reduced the stand of wild radish significantly in August 2010 (LSD = 4.20) and August 2012 (LSD = 7.11) compared to the two weeds treatments (Figure 2a & 2d). This is an indication that the use of canola as a winter cover crop may improve the control of wild radish. The stand of wild radish in the CC treatment was lower than that of the MC treatment, with the exception of 2009 and August 2012 (Figure 2d). During November 2010, August 2011, November 2011 and August 2013 this difference was significant. This supports the trends observed for weeds and Pallinup oats (Figure 2a & 2b). Canola (CC) suppressed wild radish totally in November from 2010 to 2012 (Figure 2d). The stand of wild radish in the white mustard (CC) treatment at the end of winter declined from August 2011 to August 2013. The effective control of wild radish during November must have reduced the seedbed in this treatment over time, resulting in the declining stand during winter. Canola (MC) suppressed wild radish totally in August 2012.

 

Caliente 199 (Brassica juncea cv. Caliente 199), CC and MC

Both the Caliente 199 treatments (Figure 2e) reduced the stand of wild radish significantly in August 2010 (LSD = 4.20) and August 2012 (LSD = 7.11) compared to the two weeds treatments (Figure 2a). This is an indication that the use of Caliente 199 as a winter cover crop may improve the control of wild radish. The stand of wild radish in the CC treatment was lower than that of the MC treatment, except in August 2011 (Figure 2e). The differences were significant during November 2011 and November 2012. This supports the trends observed for the weeds, Pallinup oats and canola treatments (Figure 2a, 2b & 2d). Caliente 199 (CC) suppressed wild radish totally in August 2009, November 2010 and November 2012 (Figure 2e).

 

Nemat (Eruca sativa cv. Nemat), CC and MC

Both the Nemat treatments reduced the stands of wild radish significantly in August 2010 (LSD = 4.20) and August 2012 (LSD = 7.11) compared to the two weeds treatments (Figure 2a & 2f). With the exception of November 2009, the stand of wild radish in the CC treatment was lower than that of the MC treatment (Figure 2f). The differences were significant during August 2011, November 2012 and August 2013. This supports the trends observed for weeds, Pallinup oats, canola and Caliente 199 (Figure 2a, 2b, 2d & 2e). Nemat (CC) suppressed wild radish totally in August 2009, November 2011 and November 2012. Despite the excellent control achieved with Nemat (CC), the seedbed was not reduced.

FIGURE 2. The stand of wild radish (Raphanus raphanistrum) at grapevine bud break (end of August) and grapevine berry set (end of November) measured from August 2009 to August 2013. Two management practices were applied, the one in which full surface chemical control was applied during bud break (CC) and the other in which mechanical weed control was applied in the work row and chemical weed control in the vine row (MC). These management practices were applied to the following six winter soil management practices, namely: (a) No cover crop (weeds), (b) Pallinup oats (Avena sativa cv. Pallinup), (c) white mustard (Sinapis alba cv. Braco), (d) canola (Brassica napus cv. AVJade), (e) Caliente 199 (Brassica juncea cv. Caliente 199) and (f) Nemat (Eruca sativa cv. Nemat). The values followed by different letters differ significantly at the 5% level for that specific time.

 

Summary

The use of white mustard (Sinapis alba cv. Braco), canola (Brassica napus cv. AVJade) and Caliente 199 (Brassica juncea cv. Caliente 199) can improve the control of wild radish (Raphanus raphanistrum). Full surface chemical control in the case of white mustard, canola, and a treatment in which no cover crop was sown (weeds) facilitated a decline in the stand of wild radish over time. Total control from grapevine bud break to grapevine berry set was achieved during the third and fourth seasons of implementation with the CC treatments of white mustard, canola and Nemat (Eruca sativa cv. Nemat).

 

Acknowledgements

The author thanks the ARC, Winetech and Dried Fruit Technical Services for financial support, the staff of the Soil and Water Science Department at ARC Infruitec-Nietvoorbij for technical support and Blaauwklippen Wine Estate for supplying the trial site and farm support.

 

– For further information, contact Johan Fourie at FourieJ@arc.agric.za.

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