Spray topping works on newly established lucerne

摘要

Spray topping newly established lucerne is not a recommended practice in Western Australia where experience and research is limited in this area. Farmers are reluctant to use grass-selective herbicides to control grass weeds because of herbicide resistance. They mostly rely on using trifluralin as a pre-emergent grass control. The problem is that trifluralin only gives about 80 per cent ryegrass control. This means that any surviving ryegrass can tiller extensively, becoming a problem in future years if allowed to mature and set seed. Spray topping is a common technique used on established annual pastures during spring by applying sub-lethal doses of paraquat or glyphosate to reduce grass seed set. This technique is generally not used on newly established annual legume pasture or on newly sown lucerne. Further research into the problem was conducted as part of a dryland lucerne evaluation project funded by the Grains and Research Development Corporation. A trial was established at the Wongan Hills Research Station during 2001 to determine the effects of different spray topping herbicides on newly established lucerne.