August 10, 2006
Onion growers in the Tulelake Basin may see changes in applications for
herbicides in the future.
A study in its early stages at the Intermountain Research and Extension Center
is re-examining application methods for post emergence herbicides with the
crop. Center staff are encouraged by this year’s results, but emphasize the
need for years of research ahead.
“It’s just difficult,” director Harry Carlson said.
Onions are a slow-growing crop and a particularly poor competitor as a result,
Carlson said. Weeds grow and develop much faster than the crop can, cutting it
off from water and other resources.
Herbicides were developed to help seedlings compete, but the risk of damaging
the crop by applying it too early has made application subjective. Balancing
the need for weed control and crop damage is the goal of the study, Carlson
said.
A reduced application of the herbicide earlier in the growing cycle is the
center’s main approach. Several varieties of herbicide were used in various
combinations.
Most applications were fairly successful at controlling weeds, but it was a
combination of three herbicides applied after the appearance of the first
onion flag leaves that was the most successful. The application controlled
weeds as well as weekly weeding would and with limited crop damage.
Carlson said it’s too early to be sure that this year’s results will hold
true for the rest of the study. Environmental factors such as temperature and
drought stress could alter the treatment’s effectiveness.
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