Chemical vegetation management in Pinus radiata plantations in South Africa

Gous, S. F. (1995-12)

Thesis (M. Sc.) -- University of Stellenbosch, 1995.

Thesis

ENGLISH SUMMARY: Pinus radiata is the most important timber tree planted in the western, southern and eastern Cape of South Africa, covering approximately 60000 hectares. The natural vegetation in these areas is mainly macchia, but exotic invaders like the Acacia and Hakea spp. cause severe problems. Macchia vegetation cannot be controlled successfully by means of slashing, hoeing or burning, because it resprouts rapidly in response to these treatments. Weed control in P. radiata plantations is mainly performed manually. In this study the objective was to search for an alternative, more effective, cheaper, vegetation management option to manual weeding. Trials were conducted where a number of herbicides (acetochlor, glyphosate, hexazinone, imasapir, metsulfuronmethyl, tetrapion and thiazopyr) were tested under different vegetation management treatments. These included the effect of seasons on herbicide efficacy. Preemergent herbicides were added to knockdown herbicides to test if longer relief from weeds could be obtained. Different application methods were also tested. Intra-row weeding was compared to total chemical weeding. Glyphosate at 1500g active ingredient per hectare (a.i./ha) and hexazinone at 2000g a.i./ha produced the best results for total weed control. In the southern Cape, weed control in summer was significantly better than weed control in any other season. No significant difference existed between intra-row weeding and total weeding. Chemical vegetation management was less expensive and more efficient than manual weed control.

AFRIKAANSE OPSOMMING: Pinus radiata is die belangrikste aangelante boomspesie in die westelike, suidelike en oostelike dele van Kaapland en beslaan ongeveer 60000 hektaar. Die natuurlike plantegroei in hierdie gebiede is Fynbos, maar uitheemse indringers soos die Acacia en Hakea spp. kom ook volop hier voor. Fynbos spesies kan nie met behulp van vuur- of skoffelpraktyke beheer word nie, aangesien hierdie plante herspruit nadat dit gebrand of geskoffel is. Tradisioneel was onkruide met behulp van handearbeid beheer (skoffel en afkap). In hierdie studie was gepoog om 'n meer effektiewe en goedkoper onkruidbeheermetode te vind as bogenoemde handearbeidmetodes. 'n Reeks eksperimente was uitgevoer met geselekteerde onkruiddoders (acetochlor, glifosaat, hexazinone, imasapir, metsulfuron-methyl, tetrapion en thiazopyr) onder verskillende onkruidbeheerpraktyke. Onkruidbeheerpraktyke het ingesluit die invloed van seisoene op onkruiddodereffektiwiteit, verskillende toedieningsmetodes en onkruiddodermengsels. bespuiting. Intrary bespuiting was vergelyk met totale area Glifosaat teen 1500g aktiewe bestandeel per hektaar (a. b./ha) en hexazinone teen 2000g a. b./ha het die beste resultate gelewer vir totale onkruidbeheer. In die Suidkaap was onkruidbeheer in die somer beduidend beter as toediening in enige ander seisoen. Geen beduidende verskille het ontstaan tussen interry- en totale area beheer nie. Chemiese onkruidbeheer was goedkoper en meer effektief as hanbeheermetodes.

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