COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

spring. Chemical control will simultaneously prevent ryegrasses ( Lolium species) from completing their life cycles.

Ryegrasses are weeds that readily become resistant to the post-emergence herbicides available to grapevine producers. Ryegrasses compete aggressively with the afore-mentioned annual grasses, as well as with other cover crops, and can dominate within four seasons, if allowed to produce viable seeds. At this stage, control of ryegrass becomes almost impossible. To remove the competition of winter-growing broad-leaved weeds, a broadleaf-specific herbicide

FAILURE TO APPLY CHEMICAL WEED CONTROL DURING THE EARLY GROWING SEASON RISKS ALLOWING RYEGRASSES TO DOMINATE.

can be sprayed during winter after grapevine leaf fall, to promote dry-matter production by the four winter-growing grasses that can be used as cover crops. Oat-seed grass ( Ehrharta longiflora ) Oat-seed grass is an indigenous annual grass. Initially the grass forms a loose tussock that becomes denser with maturity. The stems may grow up to 90 centimetres tall.A distinguishing feature of this grass is a purple band where the leaf-sheath merges into the leaf-blade. Conspicuous, purple-coloured bracts or glumes occur at the base of each flower. Oat-seed grass is sometimes confused with wild oats, an Avena species.

FIGURE 3.24. Oat-seed grass ( Ehrharta longiflora ). (Photos: ARC Infruitec-Nietvoorbij & Anna Mouton).

73