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Cut-leaved Crane’s-bill (Geranium dissectum) and Dove’s-foot Crane’s-bill (Geranium molle) are the two crane’s-bill species most commonly found as weeds of arable crops, although round-leaved crane’s-bill (Geranium rotundifolium) and small-flowered crane`s-bill (Geranium pusillum) may also be found as weeds. Many other Geranium species also occur in the UK, but rarely as arable weeds. Both cut-leaved and dove’s-foot crane’s-bill occur in a variety of habitats throughout most parts of the UK but cut-leaved crane’s-bill is the species more commonly encountered and has become increasingly common as an arable weed during the past 30 years.
Cut-leaved crane’s-bill is a short/medium, semi-upright or sprawling hairy annual up to 60 cm tall with pink-purple flowers. The leaves are deeply dissected almost to the base and the fruits are hairy or downy. Dove’s-foot crane’s-bill is similar, but tends to be shorter, up to 40 cm tall, and the leaves are more rounded and less deeply dissected, usually only to about half-way to the base, and the fruits are hairless. The cotyledons (seed leaves) of both species are broader than long, slightly asymmetrical, long-stalked and noticeably hairy. The two species are hard to tell apart at the seedling stage but the second true leaf of cut-leaved crane’s-bill has additional, small secondary lobes which are absent in dove’s-foot crane’s-bill.
Crane's-bills are moderately competitive species, with similar competitive abilities to groundsel, red dead-nettle and speedwells. It has been estimated that, on average, a population of 62.5 plants2 can cause a 5% yield loss in wheat crops. They may be more competitive in winter oil-seed rape. See other information sheet: How competitive are different weed species. In the past, crane's-bill seeds were often serious contaminants of seed crops, especially clover, but improved seed cleaning has greatly reduced this risk.
As annual broad-leaved weeds, crane’s-bills are propagated solely by seeds. Both species flower from April to September with seeds being shed from June. The numbers of seeds produced per plant in a competitive crop situation is normally less than 500 but, in the absence of strong crop competition, many more (>2500 per plant) may be produced. Some seeds can germinate soon after shedding and consequently seedling emergence tends to be highest in August/September. This may help explain why crane’s-bills are often associated with early-sown winter oil-seed rape crops. However, some seeds show greater dormancy, resulting in a more protracted germination period which tends to peak again in late spring.
Seedlings can only emerge from seeds within the surface 5 cm of soil. Persistence of cut-leaved crane’s-bill seed in the soil is generally considered to be relatively low (<5 years) compared with many other broad-leaved species. Seeds of dove’s-foot crane’s-bill are more persistent (> 5 years).
See other information sheet (Broad-leaved weeds: occurrence, agro-ecology and management) for the best approaches to integrated weed management of crane’s-bills. The limitations of these mean that control is largely dependent on herbicides on most farms, so maintaining the availability and efficacy of a wide range of herbicides is essential. It is worth emphasising that, as explained above, prevention of seed return over a period of years should greatly reduce the threat from cut-leaved crane’s-bill as the seedbank should decline more rapidly than for many other major broad-leaved weeds (e.g. charlock and poppy).
Herbicides and resistance
- Several herbicides are available for control of crane’s-bill, at least in major arable crops. However, with some of these, good control can only be achieved pre-emergence or by applications to young plants. Consequently, a primary aim must be to treat crane’s-bill plants while they are small.
- Some pre-emergence herbicides applied primarily for black-grass control in winter cereals, such as prosulfocarb, also give useful control of autumn emerging crane’s-bill but are unlikely to adequately control plants subsequently emerging in spring. Prosulfocarb can also be used to control crane’s bill in potatoes.
- In cereals, sulfonylurea herbicides such as metsulfuron+tribenuron can give good control of small plants but restrictions on application to after 1 February may mean that plants are too large for effective control. Sulfonylurea and related herbicides which can be applied in autumn, such as pyroxsulam+florasulam, may be a better option.
- The formulated mixture of chlorotoluron+diflufenican+pendimethalin can also control crane’s-bill species in cereal crops.
- The older synthetic auxin herbicides, such as MCPA and mecoprop, give poor control of crane’s-bills, but the new synthetic auxin herbicide halauxifen-methyl (‘Arylex’), formulated in mixture with fluroxypyr or florasulam, gives good control (although only small-flowered crane’s-bill is on the label).
- In winter oil-seed rape, clomazone+napropamide (pre-emergence only), and dimethenamid (only available in mixtures with metazachlor and/or quinmerac) can give good control of crane’s-bill post-emergence. Imazamox+quinmerac (applied before 9th true leaf stage of the crop) also gives control but can only be used in ‘Clearfield’ varieties.
- No cases of herbicide resistant crane’s-bill (or other Geranium spp.) have been detected in the UK or, indeed, worldwide. Consequently, crane’s-bill can be considered a ‘low resistance risk’ weed based on global experience but should not be consider a ‘no resistance risk’ weed due to the high dependency on herbicides for control. If resistance is suspected, collect a seed sample and have it tested.