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Herbicide Resistance Testing
Over-reliance on a much smaller range of herbicide modes of action has led to an increased risk of herbicide resistance developing to any given active. In the UK there are now four main grass weeds and three broadleaved weeds affected by herbicide resistance. At ADAS, we have over 30 years experience with testing herbicide resistance in these weeds. We offer both standard and bespoke grass weed herbicide testing for black-grass, Italian ryegrass, wild oats, and brome. A standard test costs £240.
Order a grass weed herbicide test
We also offer ALS-inhibitor (sulfonylurea) resistance testing for broadleaved weeds: mayweed, poppy, and chickweed. A broadleaved weed test costs £150.
Order a broadleaved weed herbicide test
If there has been a gradual decline in weed control over several years, this may indicate herbicide resistance. You may also notice that one weed type seems increasingly hard to control while others remain well-controlled. Herbicide resistant weeds tend to occur in species-specific patches, so healthy weed patches may be found beside dead weeds of the same species.
Ideally, fields should be tested every three years to coincide with a typical three year rotation. Understanding the resistance profile of the grass weed population in the field will help to optimise control measures.
Herbicide resistance risk could be increased by:- Repetitive application of herbicides with the same mode of action
- Multiple herbicide applications during the same growing season
- A lack of non-chemical management
- Using herbicides with long residual periods
- A lack of crop rotation
- Reduced or less effective dose rates of herbicide are applied
Once you have placed your grass weed order or broadleaved weed order, and collected your seed sample, place your name, address and field identification outside of the envelope or bag and send by 1st Class Post to: Herbicide Resistance Tests, ADAS Boxworth, Cambridge, CB23 4NN.
Once we receive your sample, ADAS will acknowledge with a receipt. As most grass weeds have a dormancy period testing will not begin until 2-4 weeks after seeds arrive. Tests then take 8-10 weeks to complete with tests being sown every 2-3 weeks.
Please note, samples with poor germination may result in delayed or failed tests.
Results will be sent as soon as they are available. As a guide, if seeds are received by the end of July, results will normally be available by the end of September. Samples must be received by 1 October to guarantee testing in the year of collection.
Your results will come with a guidance document which will explain what tests were done and our interpretation of the results. For grass weeds, we will also calculate a resistance rating for your sample(s) using the UK resistance-rating ‘R’ rating system.
Resistance rating
- RRR – Resistance confirmed, highly likely to reduce herbicide performance
- RR – Resistance confirmed, probably reducing herbicide performance
- R? – Early indications that resistance may be developing, possibly reducing herbicide performance
- S – Susceptible