Crop Action Article - Weeds in Cereals update Aug'22

Herbicide resistance is an ever-present threat to herbicide efficacy in the most commonly encountered grass weeds in the UK. Resistance levels are highest in black-grass followed by Italian ryegrass. Levels are low in wild oats and very low in brome but when resistance occurs populations can spiral out of control and remain a problem due to seed in the seedbank for many years.

In recent years we have reported cases of herbicide resistance to ALS-inhibitor herbicides (HRAC group 2) in one great, four sterile, two meadow and four rye brome populations. Herbicide resistance is present in brome species and in 2021 we found a further population of meadow brome resistant to this type of herbicide.  For further information see AHDB Project 636 (Cook et al., 2021).

Grass weeds are now beginning to shed seed, which is earlier than usual. If you have had poor control, it is a good time to collect and post samples for herbicide resistance testing. Please post samples to us as soon as they have been collected. Testing will commence from 1^st September.

Where to sample: At random from across the field or area, ensuring a representative sample

How to sample: Collect when seed is starting to shed, remove seed from the heads by gentle rubbing.

• Collect enough dry, ripe seed to fill a mug. 
• If damp, seed should be dried in an open tray before dispatch.
• Store dry seed in a paper envelope.  Do not store seed in plastic bags as it will go mouldy. 
• Mark each envelope or seed container clearly with your name and address.

We offer testing over a range of herbicides in the below table 1: -