Effective use of pre-emergence herbicides in small grain production
HESTIA NIENABER, ARC-SMALL GRAIN INSTITUTE
There are various options with regards to weed control in small grain production; however the preferred way is the routine use of herbicides.
In earlier years, producers relied significantly on post-emergence herbicides for the effective control of weeds in small grain production. Post-emergence herbicides are used after the crop has reached a certain stage. Examples are:
Group A mode of action herbicides – better known as ‘Fops’, ‘Dims’ and ‘Dens’;
Group B mode of action herbicides – better known as SU’s, Imidazolinones and Triazolopyrimidines;
Group C3 mode of action herbicides – better known as inhibitors of photosynthesis at photosystem II
Group N mode of action herbicides – better known as inhibitors of lipid synthesis (but not ACCase/Group A) herbicides; and
Group O mode of action herbicides – better known as synthetic auxins.
In recent years, many weeds, and especially so in the small grain production areas of the Western Cape, have however developed resistance to post-emergence herbicides and thus post-emergence control of weeds are not as effective as it used to be.
Herbicide resistant weeds include grass weeds (e.g. ryegrass, wild oats) and broad-leaved weeds (e.g. wild radish). Therefore, the use of pre-(crop)emergence herbicides as a method of weed control is becoming more common.
Publication: April 2011
Section: Input Overview