Effective use of pre-emergence herbicides in small grain production

April 2011

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.

Complete article

Publication: April 2011

Section: Input Overview