Blackgrass Control

Key Points

  • Shifting trends in farming practice have encouraged the prevalence of this weed.
  • One plant is capable of producing 20 tillers and each seed head can produce 200 seeds.
  • According to the plant competitive index, the presence of just 12.5 plants/m2 can cause 5% yield loss.
  • UNITE and Broadway Sunrise offer excellent post-emergence control of blackgrass and other grassweeds.
  • Rotational control of blackgrass can be achieved using Kerb Flo 500 in oilseed rape, which provides excellent control of blackgrass and other grass weeds.

Introduction

Identification - Blackgrass is an annual weed that can reach heights of 80-90cm. The stems are round and slender with few nodes. The leaves are hairless with no auricles and the ligule is long, blunt and finely serrated. The flowering head is a compact spike 3-6cm long, narrow and pointed, often with a purple tinge. Spikelets are single flowered with prominent awns.

Blackgrass is a major problem to UK farmers. As an individual plant it is not as competitive as wild oats, but because populations of 200-400 plants per square metre are quite common, yield penalties are severe. It has been calculated that just 12 plants/m2 can reduce yield by 5%. Seed is shed before harvest thereby replenishing the soil seedbed.

Increasing prevalence of grassweeds in cereals can be attributed to a shift in farming practice including:

  • Movement towards more profitable Autumn cropping
  • The use of minimum cultivation systems
  • A trend towards earlier drilling
  • A reduction in rotations and spring cropping
  • The straw burning ban

 

Biology
Blackgrass is particularly problematic on heavy soils or where drainage is poor and soils are wet. The major blackgrass regions are on the eastern side of the country which has traditionally been the cereal growing area of the UK.

The Blackgrass life cycle favours winter cereals grown in a minimal cultivation system. 80% seeds germinate in the autumn peaking in September-October. Seed dormancy is more prolific if the season is cool and wet. Blackgrass flowers in May-August, and seed is shed over 8 weeks, normally all before harvest. Each head can have up to 200 seeds, which can remain viable for 7-9 years in the soil.

Product Choice
UNITE and Broadway Sunrise are both based on the ALS inhibiting Pyroxsulam molecule. Both products offer an effective solution to blackgrass control when used as part of an integrated management approach. Effective post-emergence herbicides such as Unite and Broadway Sunrise give farmers greater flexibility in their cropping choice.

Optimal timing of ALS inhibitors is in the autumn, at the 1-3 leaf stage of the blackgrass and whilst the weed is actively growing. Both Broadway Sunrise and Unite can be applied to the crop from GS-11 to GS-29 for Broadway Sunrise or GS-30 for Unite, and up to GS 24 of blackgrass, offering a wide window for both autumn and spring applications. Both products have a favourable following crop profile with no cultivation restrictions.

Elsewhere in the rotation, Kerb Flo 500 will help get on top of the blackgrass problem.  Not only does it provide excellent grassweed control, there is also no known resistance, it is a stronger formulation meaning more hectares can be treated per pack, and there are no foil lids to dispose of.

UNITE is the widest spectrum graminicide in the UK controlling key grassweed species in winter wheat including blackgrass, ryegrass, brome species and wild oats. It is also active against loose silky bent, canary grass, couch (from seed) and meadow grass, as well as a number of broad-leaved weeds. Unite can be mixed with a residual herbicide to offer comprehensive treatment of blackgrass populations.  To view our video on blackgrass control in winter wheat with UNITE, click here. 

Broadway Sunrise offers excellent control of key grassweed species including blackgrass, ryegrass, brome species and wild oats in winter wheat, rye and triticale. It also offers cross-spectrum weed control against a number of key broad-leaved weeds. The combination of pyroxsulam and pendimethalin in Broadway Sunrise gives both contact and residual activity against target weeds.