The biology of Canadian weeds. 3. Lepidium draba L., L. chalepense L., L. appelianum Al-Shehbaz (updated)

Abstract

Al-Shehbaz (updated). Can. J. Plant Sci. 88: 379Á401. This paper updates an earlier paper by Mulligan and Findlay (1974) on the cruciferous weeds Lepidium draba, L. chalepense and L. appelianum (treated in the previous paper as Cardaria draba, C. chalepensis and C. pubescens, respectively). Known collectively as hoary cresses, these species reached North America in the 19th and early 20th centuries as contaminants in seed or in ballast. The three species spread extensively in the western parts of the continent by the mid 20th century, partly through seed dissemination, but also by establishment of clonal patches and rhizomatous spread. In the prairie provinces the three species are weeds in grainfields, hayfields and forage crops, and have been largely under control in those crops since the 1970s. By the 1970s all three species had spread into agricultural regions of south central British Columbia and remain a serious problem there. They have also spread into forest, range, and riparian areas of Alberta and British Columbia and are among weedy threats to native ecosystems. Populations in Saskatchewan and Manitoba appear to have stabilized, but remain on noxious weed lists. In the western United States, the species have also spread from cultivated areas into rangelands, and L. draba in particular competes successfully with native vegetation, resulting in reduced local biodiversity. Lepidium draba can also reduce forage production, quality and palatability. Biocontrol measures for L. draba are under investigation. Mechanical controls have proved to be generally ineffective in large populations. Herbicides are effective in the short term in some agricultural crops, but do not provide long-term control, and are of restricted use on rangelands and at riparian sites. Potential beneficial uses of Lepidium draba in phytoremediation and as a source of disease-fighting chemical derivatives are reported. e sie`cle, elles s'e´taient largement disse´mine´es dans la partie ouest du continent, en partie graˆce a`la dispersion des semences, mais aussi par clonage et propagation au moyen de rhizomes. Dans les provinces des Prairies, les trois espe`ces envahissent les champs de ce´re´ales, de foin et de plantes fourrage`res, mais on parvient a`les controˆler dans ces cultures depuis les anne´es 1970. Par la suite, les trois espe`ces ont gagne´les re´gions agricoles du centre-sud de la Colombie-Britannique ou`elles demeurent un se´rieux proble`me. Elles ont e´galement atteint les foreˆts, les grands parcours et les zones riveraines de l'Alberta et de la Colombie-Britannique ou`elles figurent parmi les adventices menac¸ant les e´cosyste`mes naturels. Les populations du Manitoba et de la Saskatchewan semblent s'eˆtre stabilise´es, mais les espe`ces restent sur la liste des mauvaises herbes nuisibles. Dans l'ouest des É tats-Unis, elles ont aussi quitte´les zones cultive´es pour les grands paˆturages et L. draba, en particulier, livre une concurrence fort efficace a`la ve´ge´tation indige`ne, ce qui nuit a`la biodiversite´locale. Le...

Phenology and temperature‐dependent development of Ceutorhynchus assimilis, a potential biological control agent for Lepidium draba

“…It is therefore likely that the stimuli triggering L. draba growth and the activity of C. assimilis after aestivation are similar. Moisture is most likely the most important factor for the formation of new L. draba rosettes after summer (Francis and Warwick ). Between June and October, precipitation is generally higher in north‐eastern Romania than in southern France (300 mm in Romania vs. 160 mm in France; multiyear averages: Romania, Iaşi weather station 2009–2014; France, USDA, ARS, EBCL –2014).…”

“…It causes important economic losses by invading many economically important crops, including peas, alfalfa, sugar beet. It can spread into adjacent rangeland grass communities and riparian areas, turning large areas into monocultures and becoming a threat to local plant communities, habitat diversity and forage production (Mulligan and Findlay 1974;McInnis et al 2003;Francis and Warwick 2008). Furthermore, L. draba contains glucosinolates that can be a serious threat to livestock health and thus may significantly affect regions with large cattle industries (McInnis et al 2003).…”

“…Broad-spectrum herbicides are widely used, but their application is limited if L. draba occurs in fields of cultivated or broad leaf crops, which do not tolerate the treatment. For effective control of L. draba, often multiple applications are needed, which are highly costly and may threaten surrounding plant communities and habitats (Francis and Warwick 2008). Mechanical control including mowing, grazing or hand pulling can be effective when combined with chemical treatments, but are limited by the large rhizome system of L. draba and phenological variability of the weed (Miller et al 1994;McInnis et al 2003).…”

Pericarp-mediated chemical dormancy controls the fruit germination of the invasive hoary cress (Lepidium draba), but not of hairy whitetop (Lepidium appelianum)

“…The noxious and invasive weeds hoary cress [Lepidium draba L.; also known as Cardaria draba (L.) Desv. or heart-podded hoary cress] and hairy whitetop (Lepidium appelianum Al-Shehbaz; also known as globe-podded hoary cress) belong to the Brassicaceae (Francis and Warwick 2008). These closely related species rank 8th out of the 45 most frequently listed noxious weeds of agricultural land, pastures, and riparian and waste areas in the western United States and Canada (Supplementary Figure S1; Mulligan 2002;Mulligan and Findlay 1974;Skinner et al 2000).…”

A new variety of the weed Borreria densiflora DC. (Rubiaceae)

“…Weeds present taxonomic diversity, not only within a genus (Sexsmith 1964; Anonymous 1981; Wang et al. 1995a,b; Francis & Warwick 2007) but also at the species level, leading to phenotypic diversity. Thus, correct identification must be considered within integrated weed management.…”