Blackgrass
Blackgrass poses a significant weed control challenge in Ireland. Blackgrass populations have been located and identified in most tillage counties but still at a low level (Figure 10). Blackgrass populations have been identified in 1980’s but the imported herbicide resistant blackgrass poses a major risk to all farms. The majority of farms do not have blackgrass and with careful stewardship this can remain the position.
Figure 1. Blackgrass heads with head on right in flower.
Figure 2. Distribution of blackgrass resistant tested by Teagasc, Oak Park.
Controlling Blackgrass on your farm
- Every farm should employ a zero tolerance policy with blackgrass.
- Careful observation and vigilance around bio-security will allow hand rogueing of any plants (before seed set) entering the farm thus preventing seed return and further populations.
- Where hand rogueing is not possible crop destruction before seed set will prevent seed build up. This area should be taken out of crop production for at least 4-5 years to manage/eliminate the weed from the field/farm.
- Farms trying to continue to “manage with blackgrass” will only lead to larger populations on the farm! The populations will continue to expand and may develop resistance, if not already present and will quickly rendering crop production unviable.
Blackgrass: Facts
- Blackgrass is the number 1 herbicide resistance weed in Europe, with the largest problem in the UK.
- Predominately autumn-germinating, between September and November with a smaller plant population establishing in spring cropping.
- Seeds have a short dormancy (< 5 years).
- Seed numbers decline rapidly (70% per year) when buried, and seeds do not emerge from > 5 cm depth.
- Innate dormancy is moderately high due to cool wet weather during seed maturation (i.e. flowering and seed formation).
- Obligate cross-pollinating –high risk of developing herbicide resistance.
- If left uncontrolled, a blackgrass plant can produce up to 600 seeds per plant but significantly more from a well tillered plant..
- Confirmed resistance in Ireland to both ACCase (eg. Falcon, Stratos Ultra) and ALS (eg. Pacifica, Monolith) herbicides. High rates of glyphosate should be used for plant destruction even when the plants are small.
Blackgrass: Identification
- Compact spike (slender) heads.
- Ligule is medium (2-4 mm), blunt and serrated.
- Leaves rolled in shoot.
- Purple leaf sheath (not all populations will have colouration)
More information on Blackgrass identification can be found below.
Figure 3. Identification of Blackgrass