Capsella bursa-pastoris
(shepherd's purse)

Annual
Broadleaved
Seed propagated

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).

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 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.

Genetics

Flowering ecotypes of C. bursa-pastoris analysed by a cosegregation of phenotypic characters (QTL) and molecular markers have identified by Linde et al., (2001).

The frequencies of the genes of low-molecular-weight alanine-rich cold shock proteins and variation of their primary structure in C. bursa-pastoris among other temperate species, have been determined by Gimalov et al., (2001).

Physiology, phenology and reproductive biology

A brief description on the biology, morphology, distribution, habitat, history and uses of Capsella bursa-pastoris have been recently published by Defelice (2001).

C. bursa-pastoris is an annual or biennial herb which grows up to 80 cm tall. It is a partially self-pollinating, autogamous plant and behaves as a quantitative long-day plant (Hurka et al., 1976). The ovule and seed morphogenesis has been studied in detail by Shamrov (2002).

C. bursa-pastoris propagates by seed, producing 5000-90,000 seeds per plant (Hurka and Haase, 1982). Norris et al. (1996) reported the production of 30,000 to 150,000 seeds by C. bursa-pastoris in the absence of competition. C. bursa-pastoris shows a high production of small and nutritive (oily) seeds of great longevity (Holzner and Numata, 1982).

A description of the complexity of germination in C. bursella-pastoris were made by Popay and Roberts (1970a, b). Most of the seeds are dormant after shedding and the dormancy is normally broken by low temperatures during the first winter. For optimal germination seeds need humidity, temperatures of about 10°C and full-spectrum sunlight. Light filtered by a plant canopy inhibits germination, as well as high carbon dioxide concentrations and darkness. Dormancy regulation ensures that some seeds are always ready to germinate if conditions become favourable and a high percentage of the seed bank stay dormant as a reserve (Holzner and Numata, 1982). This results in germination occurring throughout the year (Markov, 1976). Tillage of the soil under humid conditions exposes more seeds to light, which may lead to germination of buried seeds.

Muniz (2000) studied the influence of temperature and photoperiod on seed germination of C. bursa-pastoris and other common weeds of Spain. The author found that the optimum emergence of C. bursa-pastoris was obtained when seeds were previously subjected to -10°C for three days and then maintained in a climatic chamber under a 12-h photoperiod and constant 25°C.

The annual rate of decrease of the soil seed bank is low. Barralis et al. (1988) measured about 40% per year. Lawson et al. (1993) reported that a 99% decline of the seed bank takes between 4.3 and 6.5 years for the species C. bursa-pastoris, Poa annua, Chenopodium album and Polygonum aviculare.

The influence of germination temperature, pre-cooling, light, nitrate and water stress on the germination of 10 undesirable weeds and grasses was investigated in Germany by Ziron and Opitz von Boberfeld (2001). Among other species, C. bursa-pastoris, light and nitrate were the most important variables, except for B. hordeaceus which germinated mainly in vegetation gaps.

The morphological characteristics of seeds and the effects of environmental factors on seed emergence was investigated in C. bursa-pastoris in Japan by Shibayama and Ogawa (2000). The number of seeds per fruit varied with the ripening or harvesting period, but not with the position of the fruits. The highest germination percentage of seeds was obtained at 25°C (day)-10°C (night). The emergence pattern of seeds stored under low temperature conditions did not vary with the seed harvesting period. The germination percentage seeds was slightly higher under conditions of soil disturbance, compared to control conditions, authors report.

The lipid composition of the aerial part of C. bursa-pastoris, collected during flowering in Uzbekistan, was studied by Bekker et al., (2002). The benzene extract comprised 34.7% polar lipids, pheophytins a and b and monoacylglycerols, 12.4% diacylglycerols, sterols and chlorophylls a and b, 25.8% free fatty acids and triterpenols, 6.7% triacylglycerols, 12.8% waxy esters, 3.5% hydrocarbons, and 4.1% unidentified compounds. The CHCl3 extract was also separated by PTLC and comprised 65% polar lipids (73% glycolipids and 27% phospholipids).
C. bursa-pastoris is frost tolerant (Bonfils et al., 1991) and it shows a high phenotypic plasticity and is split up into several races (Korsmo, 1954; Holzner and Numata, 1982).

Environmental requirements

According the Milberg and Andersson (1997), the seeds of C. bursa-pastoris germinate mainly in the autumn. Light is a requirement for germination and in many cases a short light exposure (1050 µmol/m²) was enough to fulfill this requirement. Changes in seasonal dormancy were detected using this short light treatment indicating that light is not a simple, dichotomous factor in its effect on germination.

Kim Young Jin et al. (1998) studied the effect of soil chemical properties on weed development and plant coverage in pasture at 567 sites in the Korea Republic. Coverage of C. bursa-pastoris increased with rising soil pH (maximum coverage at pH >6.0) and as the exchangeable cation (Ca2+, Mg2+ and K+) content increased in the soil.

Grundy and Mead (2000) have consistently advanced in the modelling weed emergence as a function of meteorological records. Results indicated that temperature was the dominant factor in predicting emergence in five weed species among them C. bursa-pastoris. Soil moisture, while also important, was a secondary factor only becoming important once the species-specific temperature requirement had been satisfied

Associations

Significant differences in some reproductive parameters of biotypes of Bemisia tabaci with regard to four species of winter weeds were determined by Muniz (2000): the highest fecundity (eggs) and fertility (pupae and adults) were obtained with Malva parviflora L. as host, followed by Capsella bursa-pastoris. Results suggest that it is important to suppress the growth of weeds such as shepherd's purse to avoid increased populations of the pest.
Please also see section on Natural Enemies.

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.

Environmental

• Host of pest

Human food and beverage

• Vegetable

Materials

• Poisonous to mammals

Medicinal, pharmaceutical

• Traditional/folklore

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.

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.

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.

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.