Two species of Rye-grass commonly occur in the UK: Italian Rye-grass (Lolium multiflorum) and perennial Rye-grass (Lolium perenne).
Even the most intractable and costly grass weed problems can be overcome with the right management, the necessary determination and sufficient time. Understanding, commitment and flexibility are the main keys to success.
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Italian Rye-grass is very similar to Black-grass in its germination pattern, seed persistence and the depth from which seedlings can emerge.
Although herbicide resistance is currently less of an issue with Italian Rye-grass, its wide UK occurrence and the weed’s aggressive nature should make it a major concern in control programmes.
Effective cultural alongside chemical controls are, therefore, crucial for the most sustainable Italian Rye-grass management.
The best Black-grass herbicide programmes will also give effective Italian Rye-grass control, making specifically-targeted treatment only necessary where black-grass is not also a problem.
WARNING: As well as having a greater potential for rapid spread than Black-grass, Italian Rye-grass is a more competitive weed, making effective early control of infestations even more important.
Rotational ploughing can give excellent immediate Italian Rye-grass as well as Black-grass control, especially where years of shallow tillage have kept the weed seed bank near the soil surface.
Ploughing will not be as effective where Italian Rye-grass seed is spread throughout the soil profile and ploughing again within 4-5 years can bring viable seeds back to the surface to germinate.
Several years of shallow tillage is recommended after ploughing to keep any remaining weed seed near the surface where it can be controlled with glyphosate stale seedbeds.
WARNING: For the greatest control ploughing needs to give complete soil inversion and bury all trash. Otherwise, too much Italian Rye-grass seed will escape burial to a depth from which it cannot emerge.
Although Italian Rye-grass is still reasonably well-controlled with herbicides in most cases, cultural controls should always be integrated with the most appropriate spraying programmes to combat resistance development.
Pre-planting glyphosate is vital to remove all weed growth before drilling, and where planting is delayed by more than a few days a permitted glyphosate is also recommended post-planting but pre-emergence of the crop.
Residual pre-emergence cereal herbicides are essential and post-emergence treatments should be targeted at the youngest possible weeds, with herbicide actives rotated over successive seasons to minimise the risk of resistance development.
Where cereal crops still have high levels of Italian Rye-grass in the spring spraying-off patches – or even whole fields – with glyphosate will be important to limit seed return.
WARNING: If herbicide resistance is suspected, seed or plant samples should be resistance tested to establish their exact status and ensure only the most effective in-crop chemistry continues to be used.
Like Black-grass, infested fields should not be drilled with wheat until after the soil surface has become sufficiently wet to stimulate germination, allowing weed seedlings to be eliminated with glyphosate ahead of planting.
Choosing wheat varieties for the late-drilled slot on the basis of their known weed competitiveness and using higher seed rates is also advisable.
Where September drilling is important for workloads, wheat can be replaced with substantially more competitive six-row barley providing the rye-grass risk is not too high.
Spring cropping is recommended for severe infestations to allow the greatest amount of weed growth to be stimulated and sprayed-off with glyphosate before the next crop is planted.
WARNING: Without active measures to control Italian Rye-grass, neither delayed autumn drilling nor spring cropping is likely to be effective in managing the problem. Where there are high levels of weed seed in the soil profile more than one spring crop in a row may be necessary.
Full advantage should be taken of every opportunity break crops provide to control Italian Rye-grass in the rotation.
Unless preceded by winter barley, pre-planting glyphosate control opportunities are limited in winter OSR, but a range of post-emergence chemistry offers effective in-crop control.
Later sowing gives much more time for pre-planting control ahead of winter beans which also offer good in-crop control opportunities.
Spring crops offer the greatest pre-planting control opportunities – either in stubbles or through the use of cover crops sprayed off ahead of drilling – with fallowing or three year grass breaks very effective if seed return is effectively prevented.
WARNING: Less-than-ideal grassweed control has become common-place in modern cereal breaks, putting unnecessary extra pressure on management in the inherently more challenging cereal parts of the rotation.
Whenever crops are drilled, moving as little soil as possible at drilling will ‘wake-up’ the least amount of Italian Rye-grass as well as black-grass seed.
Applying as much to spring as autumn drilling, and to break and cover crops as much as cereals, this will make a useful contribution to reducing the viable seed bank in the soil.
Separate seedbed preparation in advance of drilling needs to be avoided, as do drills which actively cultivate more than the immediate drilling strip as part of their operation.
Direct and strip till drills tend to move less soil than other cultivator drill types but this may not always be the case.
WARNING: Standard tines on many cultivator drills can still move too much soil. Using narrow points has been found to substantially reduce weed emergence in the seedbed.
