COMPETITION AND CONTROL OF VOLUNTEER JERUSALEM-ARTICHOKE IN VARIOUS CROPS

A major production constraint in Jerusalem artichoke (Helianthus tuber osus L.) is caused by tubers which are nor recovered at harvest. Such lost tubers raise a serious weed problem the following season. Winter wheat, oat, spring oilseed rape, sugarbeet, maize and ryegrass were gr own in a field which had Jerusalem artichoke as the preceding crop in order to obtain information about their competitive ability and the ef ficacy of various control measurements against Jerusalem artichoke inf estation. The Jerusalem artichoke treatments in these crops were: tota l control by regular hand weeding (TOC), mechanical/chemical control(M CC), and no control (NOC). Under the NOC treatment, Jerusalem artichok e infestation at harvest was variable among crops, with the number of shoots ranging from 9 to 25 m(-2) in oat and maize stands respectively . The number of Jerusalem artichoke shoots in the MCC plots was reduce d by 50 to 99 % in oat and maize, respectively. The highest crop yield s in each of the six species were realized under the TOC treatment. In significant yield reductions were observed in the NOC treatment of whe at, oat, rape and ryegrass. However, under this management yield reduc tions of 91 and 81% occurred in sugarbeet and maize respectively. Depe nding on the preceding crop, 1-9 shoots m(-2) of Jerusalem artichoke w ere still recorded under the MCC plots in the following season. Conseq uently, for complete elimination of infestation, volunteers must be co ntrolled in the second and probably in the third year following a Jeru salem artichoke crop.