Weed control among planted and direct-seeded Eucalyptus, Acacia and Casuarina with the herbicides diphenamid, oryzalin, clopyralid and fluazifop-butyl

Summary In a glasshouse pot trial, applications of the pre-emergence herbicide oryzalin at rates equivalent to 4 and 8 kg a.i. ha−1 were toxic to germinating seeds of Eucalyptus maculata, Casuarina glauca and Acacia saligna. The pre-emergence herbicide diphenamid was toxic at rates of 7 and 14 kg a.i. ha−1 to germinating C. glauca and A. saligna, but not to E. maculata. Both oryzalin and diphenamid were selective at these rates when applied over newly-planted seedlings of Eucalyptus melliodora, Casuarina cunninghamiana and Acacia baileyana on a former pasture site. Diphenamid gave greater pre-emergence control of grass weeds, while oryzalin was more effective against the broad-leaved weeds. Overall, the most satisfactory long-term weed control and tree response was achieved with oryzalin. The post-emergence herbicides fluazifop-butyl at 0.6 and 1.2 kg a.e. ha−1 and clopyralid at 0.25 and 0.5 kg a.e. ha−1, were mostly selective to the planted seedlings on the former pasture site, but they gave unsatisfacto...