CONTROL OF VOLUNTEER ALSIKE CLOVER IN TIMOTHY GROWN FOR SEED

A study was conducted in 1-yr-old stands of timothy (Phleum pratense L.) to evaluate spring applications of several herbicide treatments for the control of volunteer alsike clover (Trifolium hybridum L.). In one 3-yr experiment, clopyralid at 0.2 kg a.i. ha-1, alone or with 2,4-D at 0.4 kg acid equivalent ha-1 effectively controlled alsike clover (flower production and the dry weight of aboveground parts were reduced by nearly 100% and 96% or more, respectively). Clopyralid at 0.1 kg ha-1, alone or with 2,4-D at 0.4 kg ha-1, and picloram/2,4-D (1:16) at 0.4 kg ha-1 provided similar control in 2 of 3 yr. In the other year, the clopyralid alone (0.1 kg ha-1) and picloram/2,4-D treatments reduced alsike clover flower production by 75% or more but the dry weight of aboveground parts was reduced by less than 55%. 2,4-D alone had little effect in reducing either the flower production or dry weight of aboveground parts of alsike clover. Seed yields of timothy were increased by herbicide treatments which provided effective control of alsike clover when vegetative growth of the latter species was vigorous. In another 3-yr experiment conducted in weedfree stands of 1-yr-old timothy, none of the above treatments had any effect on the seed yield, weight per 100 seeds or seed germination of the crop.