The objective of this study was to determine the effect of different weed management treatments on the stand of musk herons bill, one of the species that dominated the weed spectrum in the experiment vineyard, over the medium term.

 

Introduction

Musk herons bill (Erodium moschatum) is commonly found in the vineyards of the Western Cape. This procumbent to erect herbaceous weed (Figure 1a) can reach a height of 30 cm and grows mainly during winter and early spring. The stems are densely glandular-pilose. The species has a basal rosette of leaves with both surfaces being densely to sparsely pilose. The elongated styles of the five fruits that fuse into a central column is a characteristic of this weed (Figure 1b).

 

FIGURE 1. The (a) procumbent to erect habitus and

(b) leaves, flowers and seeds of musk herons bill (Erodium moschatum).

 

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 musk herons bill was determined, as fully described in Part 1 of the series.

 

 

Results and discussion

As expected, no musk herons bill occurred in the April evaluations. Therefore, the following discussion focuses on the August and November evaluations. The species was detected in all the treatments in November 2009, but not in August 2009. This is an indication that musk herons bill germinated after bud break in the MC treatments of weeds (Figure 2a) and Caliente 199 (Brassica juncea cv. Caliente 199) (Figure 2b). The same trend was detected in the CC treatments of Pallinup oats (Avena sativa cv. Pallinup) (Figure 2c), canola (Brassica napus cv. AVJade) (Figure 2d) and Nemat (Eruca sativa cv. Nemat) (Figure 2e).

 

Weeds, CC and MC

The stand of musk herons bill was, with the exception of November 2009, 2011 and 2012, lower in the MC treatment than that of the CC treatment (Figure 2a). After appearing in the MC treatment in November 2009, these differences were significant, with the exception of November 2010. Despite the species being controlled totally by the CC treatment in November 2011 and November 2012, the stand of musk herons bill at the end of winter increased continuously from August 2009 to August 2012. Although the winter stand decreased by approximately 37% from August 2012 to August 2013, the latter still amounted to an equivalent of approximately 1.54 t/ha, exceeding the stand recorded in November 2009. The trends were similar for the MC treatment, which reduced the stand in November 2010, 2011 and 2012. As for the CC treatment, the stand in August continuously increased up to 2012. Similar to the CC treatment, the stand in August declined by approximately 35% from 2012 to 2013. Although the stand in August 2013 was only 34% of that measured in November 2009, it amounted to an equivalent of approximately 0.7 t/ha, which is still significant. The results indicate that musk herons bill adapted well to the conditions in these treatments and ripened its seeds before grapevine bud break.

 

Caliente 199, CC and MC

Both the Caliente 199 treatments (Figure 2b) reduced the stand of musk herons bill significantly compared to the two weeds treatments in November 2009 (LSD = 15.30), August 2012 (LSD = 7.11) and August 2013 (LSD = 6.04) (Figure 2a). The stand of musk herons bill in both the CC and MC treatments were similar in November 2009 and August 2013 (Figure 2b), indicating that the seedbed was not reduced over time. Irrespective of the weed control practice applied, musk herons bill was controlled totally in November 2010 and November 2011. The small stand in both treatments in November 2012 could be attributed either to seeds that germinated in September, or individuals that have become resistant to glyphosate.

 

Pallinup oats, CC and MC

Pallinup oats (CC) (Figure 2c) reduced the stand of musk herons bill significantly (LSD = 15.30) compared to the two weeds treatments (Figure 2a) during November 2009. Both Pallinup oats treatments (Figure 2c) reduced the stand of musk herons bill significantly compared to the two weeds treatments in August 2012 (LSD = 7.11) and August 2013 (LSD = 6.04) (Figure 2a). The stand of musk herons bill was lower in the CC treatment than in the MC treatment, except in August 2013 (Figure 2c). Total control was achieved in November with CC from 2010 to 2012. Despite this, the stand of musk herons bill was higher in August 2013 than in November 2009, indicating that the seedbed could not be reduced by this treatment. The control in November by the MC treatment was less effective than that of the CC treatment. Although a drastic reduction in the stand of musk herons bill was recorded between November 2009 and August 2010, the August stand increased continuously from August 2009 to August 2013. As in the case of the two weeds treatments, the results indicate that musk herons bill adapted to the conditions prevalent in these treatments.

 

Canola, CC and MC

Canola (CC) (Figure 2d) reduced the stand of musk herons bill significantly (LSD = 15.30) compared to the two weeds treatments (Figure 2a) during November 2009. Both the canola treatments (Figure 2d) reduced the stand of musk herons bill significantly compared to the two weeds treatments (Figure 2a) in August 2012 (LSD = 7.11) and August 2013 (LSD = 6.04). Total control of musk herons bill was achieved with both the canola treatments in November 2011 and November 2012 (Figure 2d). Canola (MC) gave total control of musk herons bill in November 2010 as well. No definite trend was detected between CC and MC. Although the stand of musk herons bill was lower for both treatments in August 2013 than in November 2009, a clear trend was not detected to indicate a progressive depletion of the seedbed.

 

Nemat, CC and MC

Both the Nemat treatments (Figure 2e) reduced the stand of musk herons bill significantly compared to the two weeds treatments (Figure 2a) in November 2009 (LSD = 15.30), August 2012 (LSD = 7.11) and August 2013 (LSD = 6.04). Total control of musk herons bill was achieved with both the Nemat treatments in November 2011 and November 2012 (Figure 2e). Nemat (MC) controlled the weed totally in November 2010 as well. Winter-growing musk herons bill appeared in the CC treatment for the first time in August 2011 and was detected in August for the rest of the study. Although the stand of musk herons bill in August fluctuated in the MC treatment throughout the study, the stand in August 2013 was similar to that observed in the CC treatment. No trend was detected to indicate a progressive depletion of the seedbed.

 

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

Both the white mustard treatments (Figure 2f) reduced the stand of musk herons bill significantly compared to the two weeds treatments (Figure 2a) in November 2009 (LSD = 15.30), August 2012 (LSD = 7.11) and August 2013 (LSD = 6.04) (Figure 2a). White mustard reduced the stand of musk herons bill by 99% from November 2009 to November 2010, with total control being achieved in November 2011 and November 2012 (Figure 2f). White mustard (MC) controlled the weed totally in November 2010 and November 2011. Despite the success with the weed control measures during grapevine bud break, the stand of musk herons bill in August increased annually, with the exception of white mustard (MC) in August 2011. As in the case of the two weeds treatments, the results indicate that musk herons bill adapted to the conditions prevalent in these treatments.

 

 

 

 

 

 

FIGURE 2. The stand of musk herons bill (Erodium moschatum) at grapevine bud break and berry set measured from the end of August 2009 to the end of 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) Caliente 199 (Brassica juncea cv. Caliente 199), (c) Pallinup oats (Avena sativa cv. Pallinup), (d) canola (Brassica napus cv. AVJade), (e) Nemat (Eruca sativa cv. Nemat) and (f) white mustard (Sinapis alba cv. Braco). The values followed by different letters differ significantly at the 5% level for that specific time.

 

Summary

The increase or maintenance of the stand of musk herons bill in all the treatments during the five years of the trial indicate that the seedbed was not reduced. The observed trend also suggests that the species ripened its seeds before weed control was applied during grapevine bud break. However, all the cover crops suppressed musk herons bill significantly during the winter of the fourth and fifth year of the trial compared to the treatments in which no cover crop was sown. The weed control programs applied gave either total or acceptable control of musk herons bill during the grapevine growing season (September to April) from 2010 onwards.

 

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 more information, contact Johan Fourie at FourieJ@arc.agric.za.

 

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