Page 3 October, 2020 SARDA Ag Research News
Fall Spraying for Weed Control in Grass Seed Fields Fall applied herbicides are a practical and effective means of managing weeds in grass seed crops. A number of the more difficult to control winter annual, biennial and perennial weeds such as dandelion, narrow-leaved hawk’s-beard, volunteer clover, rough cinquefoil, stork’s-bill, scentless chamomile and flixweed tend to be more susceptible to herbicides in the fall than at other times of the year.
is no longer available but can be made by mixing Curtail M and the active ingredient florasulam. Cirpreme+MCPA ester is a relatively new herbicide mix from Corteva and has shown good potential for use on creeping red fescue and timothy.
Grass seed stands that are going into their first year of seed production are generally ideal candidates for a September herbicide application. These fields tend to have more weeds present compared to stands where a seed crop has already been harvested. Generally the weeds in newly established stands are also in better condition to spray.
Fall spraying can also provide more crop safety than spring or summer applications of herbicides such as Ally. Spring or summer spraying of Ally on a number of grass seed crops typically stunts the growth of the crop and may cause reduced seed head size, resulting in reduced seed production. Application of Ally in the fall usually does not result in long-term injury or reduced seed yields to grass seed crops such as timothy. Note that fall applied Ally has caused damage to crops such as perrenial ryegrass and tall fescue.
The herbicide selected will depend on what weeds are present and the tolerance of the grass seed crops to the herbicide. Products such as Curtail M, Prestige, Ally and Spectrum (MCPA ester+clopyralid+florasulam) are used. Spectrum
Many trials comparing products for fall spraying in grass seed crops have been done in the Peace Region. The table below shows a summary of what products work best on certain weeds when applied in the fall.
Table 1. Herbicide options and weed control ratings for fall spraying of grass seed crops. Herbicide
NLHB**
NLHB** (Group 2 Resistant)
Curtail M
Excellent
Excellent
Excellent
Poor
Poor to Fair
Excellent
Prestige
Excellent
Excellent
Excellent
Fair
Poor to Fair
Excellent
Spectrum
Excellent
Good
Excellent
Excellent
Poor to Fair
Fair
Ally
Excellent
Poor
Very Good
Excellent
Poor
Poor
Cirpreme+MCPA
Excellent
Excellent
Excellent
Excellent
Poor to Fair
Excellent
Clover
Dandelion
Canada Thistle
Rough Cinquefoil
