ABSTRACT
The Irish climate is generally unsuitable for grape vines. At Ballygagin, Co. Waterford the ‘heat summation’ figure (sum of the mean daily temperatures above 10ºC for the period April to October inclusive) is usually less than 850. This is well below the desired figure of 1100–2770 degree days. Nevertheless, small vineyards occur in several counties.
The mild, moist climate in Ireland encourages weed growth throughout much of the year. Weed control programmes developed for bush and cane fruits have been adapted for use in vineyards. These are based mainly on the use of overall and spot treatments with herbicides, supplemented occasionally by cultural control measures if appropriate.
Because the weed problem in Ireland is potentially much greater than in southern countries, most growers aim to achieve complete control. This strategy has worked well in fruit crops, an organic mulch being used on gently sloping sites where soil erosion is anticipated. Previously, a strategy based on suppressing weeds until fruit harvest and allowing weeds to develop until the following spring proved unsatisfactory on some occasions. Weed growth during the winter and the development of intractable weeds made control in the spring much more difficult with this system. It is considered that the concept of economic threshold levels is difficult to apply to weeds in fruit plantations because of the long-term nature of these crops and the likely development of a perennial weed flora in such situations.
The Dublin CEC meeting recognised that total weed-free systems carry a risk of undesirable side effects. Research in Ireland using herbicides to achieve weed-freedom has shown no adverse effect on soil structure compared with cultivation. However, more information is required on possible side effects such as the induction of new pest problems through the inhibition of natural mortality factors.
