Abstract:
Jointed goatgrass (Aegilops cylindrica Host.) is a serious weed problem in wheat
(Triticum aestivum L.) production in the United States. Studies were conducted to
determine the outcrossing rate, competitive ability, and effectiveness of certain control
practices on jointed goatgrass. A field study was conducted over two years at four
locations to determine outcrossing rates of four jointed goatgrass populations. There were
no differences in outcrossing rates among the four populations. In the first year of the
study, outcrossing was not different at any of the sites and averaged 1.28%. In the second
year, outcrossing ranged from 0.38% to 2.24%. Outcrossing rates also were measured for
wheat. Wheat outcrossing average was 0.09%, but rates ranged from 0% to 0.30%. A
second study compared the competitive ability of plants derived from seed from the
primary and secondary floret position within jointed goatgrass spikelets with winter
wheat. This study consisted of three replacement series experiments that included
pairwise combinations of the three plant types grown in five planting ratios. Jointed
goatgrass plants from the seed in the secondary floret position were equally competitive
with winter wheat and more competitive than plants from seed in the primary floret
position. A third study was conducted to determine the effect of rate and timing of
imazamox application on jointed goatgrass and imidazolinone-resistant wheat. At earlier
timings, there was no difference in jointed goatgrass response to different herbicide rates.
Wheat response was affected by herbicide rate at all application times. Pre-emergent
herbicide treatments did not affect either species. When grown in 50:50 mixtures, final
dry weights of jointed goatgrass and wheat were not affected by herbicide rate at either
the early or late application time.
