A Technical Guide for Wine Producers

RECENT ARTICLES   |   WYNBOER HOME Winter Weed Control: Early Or Late Control? J Pienaar, VinPro (SA) In most cases winter weeds are chemically sprayed in the late winter or early spring, sometimes together with the cover crop. Initially, a few decades ago, when herbicides were first used in vineyards, the practice was to apply chemical weed control early in winter, just after the emergence of the weed, probably due to the limited choice of herbicides at the time. The principle of early chemical control of young winter weeds still has advantages, however, provided it is applied in a system in which every second row is established with cover crops. Then only the berm and weed row are chemically controlled at an early stage. Depending on the climate of the particular year, weed control is applied to young weeds from late May - June, once the leaves have all dropped. The advantages of early control are: the use of a lower dose of herbicide, which is more environmentally friendly easier control, even of hardy weeds, at a young stage pruning actions are facilitated since there are no large weeds on the berm that strangle the vines more effective control (spraying) of e.g. mealybug in winter no large dead weeds that grow into the vines and serve as "insect bridges" (e.g. ants, snails) Photo 1: Cover crop every second row, with alternative rows where weeds on the berm were sprayed at an early stage (June) Photo 2: Cover crops every second row and weeds left to reach maturity. Notice the high weeds on the berm growing into the vine and complicating pruning. Photo 3: Late spraying of weed rows and berm. Notice the dead weeds in the vines acting as "insect bridges" and complicating pruning. Photo 4: Young vineyard with the plant row having been sprayed at an early stage, ± 4 weeks before planting. Photo 5: Straw is placed on the berm to control weeds in a young vineyard where development of the vine will take place in the next growing season. In new plantings, where the berm or plant row was sprayed with herbicide approximately 4 weeks before planting, the planting action is facilitated. The cover crop rows also serve as a windbreak to protect the young vines. Another advantage is that the soil of the "berm" is able to absorb heat more readily, thus promoting root growth.

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