Silene latifolia subsp. alba
(white campion)

S. latifolia subsp. alba is a biennial or short-lived perennial herb growing to 1 m in height, producing white, 5-petalled, showy flowers. Native to Eurasia, it has been introduced to East Asia, Australasia, and North and South America. In some introduced areas it has become a noxious invasive weed of hay fields and pastures. In North America it is a seed contaminant of lucerne (alfalfa), clover, grass and small grain seed crops. In western North America it is displacing the native and threatened Silene spaldingii.

The native range of S. latifolia subsp. alba encompasses most of Europe, from Scandinavia and the UK in the north, to the Mediterranean and western North Africa (Morocco, Algeria), then east to West Asia and through Russia as far as its Far Eastern provinces. The species has been introduced to East Asia (China, Japan), Australia, New Zealand and North America, and there are reports from South America (GBIF, 2015; USDA-ARS, 2015). In Canada it is reported from every southern Canadian province from British Columbia to Newfoundland. It is listed as a noxious weed in Alberta and as a class C noxious weed in Washington State, USA (Washington State Noxious Weed Control Board, 2010; Center for Invasive Species Management, 2014). In the USA it is found in most states, particularly in those of the north-central and north-eastern areas (USDA-ARS, 2015; USDA-NRCS, 2015).

S. latifolia subsp. alba can be introduced to new areas by accidental inclusion as a contaminant in fodder crop seed or as a contaminant of hay imported for livestock feeding.

S. latifolia subsp. alba is commonly found in pastures and hay fields, along roadsides and rights-of-way, on grass embankments and in wasteland, as well as in many undisturbed areas (Washington State Noxious Weed Control Board, 2010). It prefers well-drained soils and is seldom seen in dry climates.  Seedlings do not tolerate high temperatures.

S. latifolia subsp. alba competes with seed crop species including lucerne, clovers, grasses such as timothy and small grains. It displaces native plants such as the threatened Silene spaldingii (US Fish and Wildlife Service, 2007).

Genetics

The chromosome number of S. latifolia subsp. alba is 2n=24 (Halkka, 1985). It hybridizes with S. dioica when both species grow in close proximity, producing offspring with pink flowers (NatureGate, 2015).

Reproductive Biology

S. latifolia subsp. alba is dioecious and thus obligatory outcrossing. Male flowers open longer than female ones in order to increase the chance of pollen dispersal by insects. The longer the flowers are open, the higher the chances that pollination will occur. Flowers usually open for more than 12 hours, from evening until mid-morning the next day, allowing a range of both diurnal and nocturnal pollinators to effect pollination. Most pollination occurs at night, the primary nocturnal pollinators being noctuid and sphingid moths. Diurnal pollinators are bees, flies and wasps (Young, 2002). Plants are profuse seed producers; a single plant produces about 50 capsules, each capsule containing about 500 seeds (Frendahl and Anderson, 2013).

S. latifolia is a key plant model in the study of sex determination and sex chromosome evolution (Kejnovsky and Vyskot, 2010).

Physiology and Phenology

S. latifolia subsp. alba flowers from the end of April up to the end of October, but usually has two distinct flowering peaks at the end of May and the beginning of August (Biere and Honders, 1996). 

Longevity

It is a biennial or short-lived perennial (Alberta Weed Monitoring Network, 2014).

Associations

S. latifolia subsp. alba is an alternative host or vector for Lychnis ringspot virus, which infects sugarbeet (Alberta Agriculture and Forestry, 2015).

Environmental Requirements

It can grow on light sandy, loam and heavy clay soils, with pH acid, neutral and alkaline. It prefers moist soil and cannot grow in the shade.

In western Europe, the caterpillars of the specialist Hadena bicruris, a night-active pollinating moth, are the most important herbivores consuming developing seeds of S. latifolia (Brantjes, 1976; Elzinga et al., 2005).

In North America, S. latifolia populations have become infected by the anther smut pathogen Microbotryum lychnidis-dioicae, a member of the M. violaceum complex, brought in fairly recently from Europe; the system is a well-studied model in evolutionary biology and ecology. Fontaine et al. (2013) found that the actual pathogen was likely introduced as a single population from Scotland, UK.

Environmental

• Wildlife habitat

Materials

• Chemicals

Apart from flower colour and wider leaves, S. latifolia subsp. alba is very similar to S. dioica. Two other campions, S. vulgaris (bladder campion) and S. uniflora (sea campion), are sometimes mistaken for S. latifolia subsp. alba, but S. vulgaris has branched flower stems and greatly enlarged sepal tubes (seed pods), while S. uniflora is a short plant also with swollen sepal tubes but having unbranched flower stems, each topped by a single bloom (First Nature, 2015). Furthermore, S. vulgaris is not hairy or sticky, seed capsules only have 6 teeth and the calyx has netted veins. S. noctiflora also has similar flower appearance to S. latifolia subsp. alba but is hairy and sticky, its seed capsules only have 6 teeth and the calyx has branched veins. In general, S. latifolia subsp. alba can be differentiated from similar species by having (i) white flowers with 5 lobed/notched petals; (ii) leaves that are opposite and hairy; (iii) flowers which open at night and have a pleasant odour; (iv) hairy stems which may become almost woody when mature; and (v) a tap root and lateral roots (Alberta Weed Monitoring Network, 2014).

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Prevention

To prevent the infestation of pastures and seed crops by S. latifolia subsp. alba, the use of grass and legume seed that has a Certificate of Analysis declaring it free of S. latifolia subsp. alba seed is advocated. Also, any hay for livestock feeding should be certified as free of S. latifolia subsp. alba. As it requires full sun for best growth, crops sown at high densities and vigorous forage stands can generally outcompete its seedlings; however, established campion is not significantly reduced by crop competition (Alberta Agriculture and Forestry, 2015). 

Eradication

Eradication of S. latifolia subsp. alba from S. spaldingii habitats involves the use of integrated pest management measures (US Fish and Wildlife Service, 2007).

Cultural Control and Sanitary Measures

Cultivation or tillage for seedbed preparation will kill many S. latifolia subsp. alba plants, although well-established plants generally survive cultivation, and tillage will promote weed seed germination. Tillage should be deep enough to cut off roots below the crown and deposit the plant on the soil surface to dry out. Tillage can be a suitable control method in row crops or prior to sowing small-seeded grasses or legumes. Surface tillage will also control seedlings in summer fallow situations. The addition of fertilizer to the crop, unfortunately, will enhance S. latifolia subsp. alba growth. Mowing can be effective in preventing campion seed production, but the weed can withstand annual mowing as the root will send up new shoots (Strand and Wyse, 1982; Alberta Weed Monitoring Network, 2014).

Physical/Mechanical Control

Hand pulling will work for small infestations, but the entire root must be removed (Alberta Agriculture and Forestry, 2015).

Chemical Control

Based on information from Minnesota, S. latifolia subsp. alba can be controlled in field crops by herbicide application most easily when it is at the seedling stage or during seed germination. In grass seed fields, dicamba has been shown to be the most effective, while for small-seeded legumes, benefin (benfluralin) gave the best results in new sowings. Metribuzin was among several herbicides used effectively on older stands (Strand and Wyse, 1982).

IPM

Integrated pest management practices used in controlling S. latifolia subsp. alba in S. spaldingii habitats include spot spraying of herbicides, prescribed burning and hand pulling (US Fish and Wildlife Service, 2007).

22/06/15 Original text by:

Andrew Praciak, Consultant, UK