Rat’s-tail Fescue

Occurrence

Largely confined to the southern half of England this annual grass-weed, Vulpia myuros, is increasingly found in arable fields, although it is more commonly found on waste ground, roadsides and in urban areas. A major problem in herbage seed crops due to difficulties in control and contamination of harvested samples from which it can be difficult to remove. Increasingly found in arable fields possibly as a consequence of sowing grass margins with contaminated seeds mixtures. Often seems to ‘appear from nowhere’ and may disappear just as fast. Closely related to Squirrel-tail Fescue (Vulpia bromoides) which is more widely distributed but is largely confined to man-made habitats and rarely occurs as an arable weed.

Identification and damage

Produces lax or dense panicles, often tinged purple when mature, which are usually curved or nodding. The lower part of the panicle often remains enclosed within the uppermost leaf sheath – an unusual characteristic. Glumes very unequal, with the shorter usually much less than half the length of the longer. (In Vulpia bromoides the shorter glume is usually more than half the length of the longer).There is little information on effects on yield here but increases of over 50% were recorded in USA wheat trials as a consequence of control. A serious weed of herbage seed crops.

Control Options

• Has high fecundity because of its ability to self-pollinate and produces many seeds with low dormancy and high germinability.
• Populations can increase rapidly in favourable conditions such as early sown autumn crops established with minimum cultivation or direct drilling.
• Ploughing can give very good control as this weed is shallow rooted and intolerant of tillage. Conversely, it is encouraged by shallow tillage and especially direct drilling, which greatly favours this weed.
• Predominantly an autumn emerging weed species – spring cropping can help reduce populations substantially.
• Seeds only survive 2–3 years in soil so if seed return can be prevented, populations can be reduced substantially within a few years.
• Rat’s-tail Fescue is naturally tolerant to all ACCase inhibiting herbicides so ‘fops’ (e.g. clodinafop, propaquizafop), ‘dims’ (e.g. cycloxydim, clethodim) and ‘dens‘ (e.g. pinoxaden) will not give adequate control.
• Pre-emergence, flufenacet based herbicides are the best option based on studies in the USA, Denmark and UK. Prosulfocarb and pendimethalin can also give good control but appear to be more dose dependent.
• Post-emergence, the best option in cereals are the ALS inhibitors, with mesosulfuron+iodosulfuron giving particularly good levels of control. Other ALS inhibitor, such as florasulam+pyroxsulam, propoxycarbazone and sulfosulfuron, can also give good control, but achieving the best control appears to be more dose/timing dependent than with mesosulfuron+iodosulfuron.
• In oil-seed rape, propyzamide should achieve reasonable control, especially if applied to small plants. Achieving maximum control from propyzamide is vital, as ACCase herbicides are ineffective and there are few other post-emergence options.
• Glyphosate can give good control regardless of growth stage, provided low doses are avoided, so should be effective for controlling plants before drilling or in non-crop situations.
• No cases of evolved herbicide resistance have been reported in Rat’s-tail Fescue anywhere in the world. However, resistance has been found in Australia in populations of the closely related species Squirrel-tail Fescue.
• If resistance is suspected, collect a seed sample and have it tested.