Elymus repens (quackgrass)

Cultural measures in the cropping system should always be considered. Measures improving the effect of competition in competitive crops such as small-grain cereals, oil-seed Brassica crops and many fodder crops are important. Using as small row spacings as is technically possible, and making all efforts to achieve an even distribution of the crop plants in the row, can reduce the plant growth of E. repens considerably, particularly in combination with a rapid and even emergence and establishment of the crop plants. To achieve rapid crop establishment, seedbed preparation and sowing depth adapted to soil type and climate are of the utmost importance (Håkansson, 1974, 1979, 1995). Systematic combination of techniques aimed at optimizing the competition from a potentially competitive crops, such as small grain cereals, may reduce the growth of E. repens by 50%.

Although considerable effects can be obtained by enhancing competition in certain crops, additional control is usually needed. When crops are harvested long before the end of the growing season, E. repens has its best period of rhizome production after harvest, in a period free of competition from the crop. Changing this period of production into reduction by mechanical or chemical control is a most effective measure in a control system for E. repens. When soil cultivation is carried out, the first operation (stubble cultivation) is preferably done immediately after harvest, with implements breaking the rhizomes as much as possible (Håkansson, 1968b; Boström and Fogelfors, 1999). When the growing period is long enough, operations are repeated at intervals. Ploughing is the last operation before winter or, on certain soils, it can be done in early spring if therew is enough time before the final seedbed preparation and sowing of the next crop. According to Håkansson (1974, 1982, 1995), combination of such tillage and competition in good stands of crops such as small-grain cereals will suppress E. repens and similar weeds by 90% or more.Without effective tillage, E. repens, like other creeping perennial weeds, is hard to control sufficiently by any means except herbicides. This is illustrated in many experiments with reduced tillage in various forms (for example, Bachthaler, 1974; Cussans, 1976; Rydberg, 1992; Børresen and Njøs, 1994; Skuterud et al., 1996; Dzienia and Piskier, 1998).

Where mechanical control is not desirable or not possible due to soil or climate, or for other reasons, different herbicides can be used for controlling grasses such as E. repens. Some of the more important ones are presented below.A number of systemic foliar herbicides are effective on E. repens when the plants have sufficient actively growing aerial shoots in proportion to the attached rhizome system. The most important is glyphosate, a herbicide with low selectivity, used in a large number of countries with good effect in controlling E. repens. It is used in stubble fields after harvest, on fallow land, in orchards, on grassland in connection with ploughing (either before or following ploughing after sufficient time), in field margins and headlands, and in some countries, in ripe cereals e.g. by wiping or even spraying overall before harvest. Examples of other herbicides used for the control of E. repens are sethoxydime and cycloxydime, which are selective herbicides used in a number of dicotyledonous crops such as rape, turnip rape, beet, potatoes and peas. In recent years, other herbicides of this type, such as tepraloxydim (Kibler et al., 1999) have been used successfully in many of the crops mentioned. Foliar-applied herbicides of the sulfuro group may also be of interest for controlling E. repens, for example, sulfuron in potatoes (Kuzior et al., 1999), wheat (Rainbolt et al., 1999) and in fields of stubble (Rola et al., 2000). This and other herbicides of this group might attract an increasing interest in the control of E. repens in different cereals (e.g. Feucht et al., 1999). Various adjuvants are of interest for increasing the effect of sulfuron and other herbicides (Woznica et al., 1998). Among selective herbicides for soil application, EPTC has been used for several decades and is still used in some countries in dicotyledonous crops, e.g. in potatoes before planting. Propyzamide and terbacil are used in some countries, e.g. in orchards.