Capsella bursa-pastoris (shepherd's purse)

C. bursa-pastoris is an annual or biennial small, erect herb that reproduces by seed.The height is variable, ranging from 5 to 80 cm. Stems are erect, solitary or branched from the base, striate, glabrous or sparsely haired (hairs simple or branched) and pale green. The root is a thin taproot which is sometimes branched. The basal leaves are petioled, oblanceolate with a blunt tip and are commonly deeply lobed. They are 15 cm long, 4 cm wide and spread in a rosette form (Holm et al., 1977). The upper stem leaves are smaller (8 cm long, 1.5 cm wide), alternate, sessile and clasping the stem with ear-like projections.The flowers are white in long terminal racemes with a pinkish or green calyx, a white corolla and four obovate petals of 2 mm length. The pod (silique) is flattened, triangular, notched at the apex and stalked. Each pod contains about 20 seeds attached to a thin membranous septa. The seed is about 1 mm long, oblong, orange-yellow with a dull and punctured surface.

C. bursa-pastoris is a cosmopolitan species which originated in Europe. It has now spread and grows throughout the temperate parts of the world (Ivens, 1971). According to Terry and Michieka (1987), it is also abundant in eastern Africa at higher altitudes.C. bursa-pastoris invades almost all kinds of crops in ample regions. The information available is not enough to complete a detailed and precise statement for which countries (and eventually regions or provinces) is invasive/not invasive.

Three habitat characteristics that are generally thought to encourage invasions are disturbances, low species richness and high resource availability. The impact of an invasive plant depends on the area covered by the species and its abundance (Booth et al., 2003). It is difficult to predict which ones will become pests and often it is simply the characteristics of a particular place that allows an introduced species to become invasive. (Williamson et al., 2003).

Seeds of C. bursa-pastoris have a mucilaginous epidermis which, when moist, attaches the seeds to animals or other transport vehicles and allows long distance dispersion. The ingestion of seeds by earthworms seems to play an important role in vertical short-distance transport in soils (Hurka and Haase, 1982).

C. bursa-pastoris is a weed in cultivated fields in all temperate areas of the world, including higher altitudes in the tropics and sub-tropics. It will grow on many soil types and in many crops.

C. bursa-pastoris may be confused with Capsella rubella; the convexity of the pod is a key factor in differentiation (Kissmann and Groth, 1993).C. bursa-pastoris is extremely variable in size, fruit and leaf form. It can be distinguished by its long terminal racemes and triangular pods, its white flowers and by the deeply lobed basal leaves which form a rosette.

C. bursa-pastoris is present on arable land in nearly all temperate parts of the world in practically all crops, gardens, lawns, non-cultivated areas, roadsides and waste grounds. It grows on all soils and has very flexible ecological requirements (Holm et al., 1977).

C. bursa-pastoris serves as a host for insects, fungi and viruses, including many insect pests and diseases of crops.It is a winter host to Aphis gossypii (Hosoda et al., 1993) and Thrips palmi (Nagai and Tsumuki, 1990) in Japan. Overwintering of Myzus ascalonicus is reported by Karl (1983) in Germany. It is also host to Brevicoryne brassicae (Gabrys et al., 1999), Lygus sp. (Khamraev, 1999) and Ceutorhynchus albosuturalis (Hong KiJeong et al., 2000).C. bursa-pastoris is a host to Sclerotinia sclerotiorum (Hance and Holly, 1990), Peronospora parasitica (Tewari, 1993) and Albuga candida (Sansome and Sansome, 1974).The following viruses were found on C. bursa-pastoris: Beet yellows virus (BYV), Beet western yellows virus (BWYV) (Paczuski and Blachowska, 1992) and Cucumber mosaic virus (CMV) (Conti et al., 1979). Holm et al. (1977) lists the following viruses: anemone mosaic virus [Turnip mosaic virus], Aster yellows virus, Beet curly top virus, Beet mosaic virus, beet ringspot virus [Tomato black ring virus], cabbage black ringspot virus [Turnip mosaic virus], cabbage ring necrosis virus [Turnip mosaic virus], Cauliflower mosaic virus, Tobacco broad ringspot virus, Tobacco mosaic virus, Tobacco ringspot virus, Turnip crinkle virus, clover big vein virus [Clover wound tumor virus], potato yellow dwarf virus [Potato yellow dwarf virus], Radish mosaic comovirus and Turnip yellow mosaic virus.C. bursa-pastoris is also reported to be a host for the sugarbeet nematode Heterodera schachtii (Gleissl and Bachthaler, 1988; Gleissl et al., 1989) and the soyabean cyst nematode Heterodera glycines (Ramarao Venkatesh et al., 2000).Capsella bursapastoris among other weeds were found to be highly susceptible to Verticillum dahliae in Greece (Ligoxigakis et al., 2002) reports.Capsella bursa-pastoris among other weeds have been found to host Alfalfa mosaic virus, Cucumber mosaic virus, Potato virus Y, Soybean dwarf virus, and Tomato spotted wilt virus in New Zealand, Fletcher (2001) reports.

C. bursa-pastoris generally does not give any serious problems on arable land under short rotations. Although readily controlled by cultivation, C. bursa-pastoris produces large quantities of seed and therefore dense infestations can form a serious weed problem in some cases (Ivens, 1971).Studies carried out in a wheat field in China by Yu-JinFeng et al., (2002) determined that the eco-economic threshold period (ETP) was of 180-200 plants/m2 of broad-leaved weeds such as C. bursa-pastoris, Descurainia sophia and Silene conoidea.Suspected nitrite poisoning in pigs caused by Capsella bursa-pastoris has been suggested by Wiese and Joubert (2001).C. bursa-pastoris may be important as an alternative host of many plant pathogens causing crop damage. See Natural Enemies for further details.

The nutritional composition of wild crucifer species has been determined by Guil Guerrero et al (1999). Authors found that the omega-3 series of fatty acids were predominant in C. bursa-pastoris.Dog et al., (2001), under an integrative approach studied the effects of herbal remedies for menstrual flooding and irregularities during menopause, which include chastetree fruits and shepherd's purse (C. bursa-pastoris).

In China C. bursa-pastoris is an important wild vegetable exploited for its taste, nutritional value and medicinal characteristics (Wu Zhou, 1998).

C. bursa-pastoris is extremely variable in size, fruit and leaf form. It can be distinguished by its long terminal racemes and its triangular pods, its white flowers and by the deeply lobed basal leaves which form a rosette.

Cultural Control 

The addition of Brassica hirta to air-dried soil (20g/400 g soil) reduced the emergence of C. bursa-pastoris by 97% (Al Khatib et al., 1997).

C. bursa-pastoris in apple orchards was suppressed by the dominance of water foxtail (Alopecurus aequalis var. amurensis) in the Korea Republic (Jung et al., 1998).
The effects of grazing intensity on weed populations in annual and perennial pasture systems has been studied by Harker et al., (2000) in the USA. In perennial pastures, each unit increase in grazing intensity led to 51 more C. bursa-pastoris per m². At lower levels of grazing intensity, C. bursa-pastoris and other species were most abundant in the annual pastures. The response of the weed population to grazing pressure in annual pasture systems is restricted because of annual tillage and MCPA. Therefore, pasture managers may subject annual pastures to heavy grazing pressure with less negative weed population consequences than perennial pastures where herbicides are not applied.

Tillage for seedbed preparation in the annual system supports a proliferation of annual weeds in the spring.

Manual and Mechanical Control

C. bursa-pastoris can be readily controlled by conventional manual and mechanical weeding. The influence of four tillage systems, varying from intensive to zero tillage, on weed populations and the vertical distribution of weed seeds in the soil was determined by O´Donovan and Mc Andrew in Canada (2000). The winter annuals such as shepherd's-purse (C. bursa-pastoris) increased in the soil seedbank as tillage was reduced, however, higher populations in the soil seedbank did not always result in higher spring seedling populations under zero tillage.

Chemical Control

Many products are available for control of C. bursa-pastoris. It is susceptible to the action of auxin-type growth-regulators and to most contact and residual herbicides (Ivens, 1971). Good control is achieved using sulfonylureas (Eberlein et al., 1994), amidosulfuron, metsulfuron-methyl (D'Sousa et al., 1993), thifensulfuron (Müller, 1992), chlorsulfuron (Rudfeldt, 1983), substituted ureas (Baumann, 1994), acetanilides (Penner et al., 1993), imidazolinones (Miller, 1986; D'Sousa et al., 1993) and triazines. These herbicides are often used in mixtures and sequences with other herbicides to achieve optimum control of the weed.

Post-emergence application of imazethapyr during establishment following pre-plant application of trifluralin consistently provided 80% control of Avena fatua and C. bursa-pastoris without any injury to the crop (Darwent et al., 1997). According to Lueschen et al. (1997), only post-emergence aplications of imazamox gave good control of C. bursa-pastoris. Pre- and post-emergence applications of rimsulfuron gave good control of C. bursa-pastoris in tomato (Mullen et al., 1999). Isoxaflutole provided effective control of annual broad-leaved weeds including C. bursa-pastoris in maize (Dorontic and Loubiere, 1999). Isoproturon + amidosulfuron effectively controlled important weeds of winter cereals including C. bursa-pastoris (Cimerman and Babnik, 1999).

In experiments conducted in wheat fields from 1993-1997 a range of sulfonylurea herbicides controlled broad-leaved weeds including C. bursa-pastoris by more than 90%. However, continued use of sulfonylureas year after year caused a shift in the weed community (Jiang DeFeng et al., 1999).

Sulfosulfuron may be used in potatoes, providing more than 90% control of C. bursa-pastoris (Gough and Calstrom, 1999). Clomazone may also be used in this crop (Genot et al., 2000).

A chemical weed control trial conducted by Montemurro et al., (2000) in a 10-year-old olive orchard (Italy) demonstrated that all rates of azafenidin at single application showed high and lasting levels of efficacy in controlling Anthemis arvensis, Capsella bursa-pastoris, Conyza canadensis, Diplotaxis erucoides, Sonchus oleraceus, Lolium spp. and Poa spp. The herbicide treatments tested did not have significant effect on crop yield when compared with tilled control.

Montemurro and Facchiolla (2000) report that azafenidin gave consistent control of C. bursa-pastoris among other weeds without any damage to olives.

A comparative survey of weeds surviving in triazine-tolerant (TT) and conventional (C) canola crops in south-eastern Australia have been recently made by Lemerle et al., (2001).They found that some weeds were more prevalent in (C) canola (e.g. Fumaria spp., Arctotheca calendula, Capsella bursa-pastoris and Papaver somniferum) while others were more common in TT canola (e.g. Anagallis arvensis, Raphanus raphanistrum, Lepidium africanum and Conringia orientalis). Results suggest that widespread adoption of TT canola will affect weed population dynamics, thereby leading to new weed problems.

Integrated Control

Fennimore and Jackson (2003) have evaluated the effects of minimum tillage vs. conventional tillage and the effects of organic amendments (cover crops and compost) vs. no organic amendments in vegetable fields in USA. Reduced tillage increased the density of shepherd's-purse (Capsella bursa-pastoris) in the upper soil layer (0 to 15 cm) of the soil seed bank compared with conventional tillage. Also shepherd's-purse emergence and seed bank densities were lower in the organic amendment plots, authors report.