Lepidium draba (hoary cress).

Lepidium draba is found in a wide range of habitats ranging from roadsides (highly disturbed sites) to rangelands, meadows and pastures, cultivated fields, home gardens, national parks and wasteland. It exists at high and low latitudes, above and below sea level. It is found under irrigation and in soils of high moisture content and also exists in arid regions. It invades all soil types, although it prefers alkaline conditions and can germinate in saline soils. All of these characteristics and adaptations provide exceptional advantages for this noxious weed and reflect its high potential to invade different agricultural systems. The absence of L. draba plants from plantations or sites where it has not been reported may not be due to the species' ability to invade, survive, grow or develop in these sites but rather to the absence of initial infestation. The weed can invade both agricultural and natural ecosystems (Larson et al., 2000). In summary, L. draba is a serious threat to agriculture and the environment. It is of a high ecological tolerance and is potentially harmful to human and animal health. Its ability to invade and reproduce by different means and to host plant pathogenic agents make this weed invasive with significant problems to man and natural resources.

Broadleaf weed control in rain-fed chickpea

Weeds are among the main limitations on chickpea production in Iran. The efficacy of herbicide treatments including linuron PPI, imazethapyr PPI, PRE, and POST, pendimethalin PPI and POST, bentazon POST, pyridate POST, and oxadiazon POST along with one or two hand weedings were evaluated for weed control and yield response in rain-fed chickpea in Aleshtar, Lorestan, Iran in 2015 and 2016. Wild safflower, threehorn bedstraw, wild mustard, and hoary cress were the predominant weed species in both experimental years. Total weed dry biomass in weedy check plots averaged 187 and 238 g m−2 in 2015 and 2016, respectively, and weed density and biomass were reduced in all treatments compared to the weedy check in both years. Treatments composed of pyridate followed by one hand weeding or imazethapyr POST followed by two hand weedings resulted in the lowest weed biomass. The presence of weeds reduced yield by 74% and 66% in the weedy check plots compared to the weed-free control plots in 2015 and 2016, respectively. Application of oxadiazon, bentazon, and imazethapyr PPI, PRE, and POST resulted in lower chickpea yields. All herbicides tested injured chickpea slightly, with pyridate causing the least injury.

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

This study provides a comparative analysis of the dormancy and germination mechanisms of the indehiscent fruits of hoary cress (Lepidium draba L.) and hairy whitetop (Lepidium appelianum Al-Shehbaz), two invasive weeds of the Brassicaceae. Germination assays comparing isolated seeds (manually removed from the fruits) and intact indehiscent fruits showed that the isolated seeds are nondormant and provided full germination for both species. In contrast to this, the species differed in the germination properties of their indehiscent fruits, in that L. appelianum fruits were nondormant, while the L. draba fruit coat (pericarp) conferred a coat-imposed dormancy. The pericarp of L. draba fresh fruit was water permeable, and neither mechanical scarification nor surface sterilization affected germination, supporting the concept that pericarp-mediated dormancy was not due to water impermeability or mechanical constraint. Washing of L. draba fruits with water, afterripening (dry storage), and treatment with gibberellin (GA) stimulated the germination of this species, all of which are indicative of physiological dormancy. Analyses of endogenous abscisic acid (ABA) and GA levels combined with treatment experiments with wash water from fresh and afterripened L. draba pericarps and with ABA dose–response quantification of germination revealed that ABA is a key component of a pericarp-mediated chemical dormancy in this species. Consistent with this, pericarp ABA levels decreased during afterripening and upon fruit washing, and isolated fresh or afterripened seeds did not differ in their ABA sensitivities. The possible roles of the ABA-mediated pericarp dormancy for the germination ecophysiology and weed management of these species are discussed.

Assessment of Allelopathic Potential of Fennel, Rue and Sage on Weed Species Hoary Cress (Lepidium draba)

The current series of experiments was conducted to assess the allelopathic potential of fennel, rue, and sage seed and plant biomass on weed species hoary cress (Lepidium draba). The effect of plants was evaluated through: seed cogermination in Petri dishes, effect of water extracts from fresh and dry plant biomass in two concentrations (50 and 100 g l-1) in Petri dishes and pots, and effect of fresh and dry plant residues in rates of 10 and 20 g kg-1 of soil. The cogermination of seeds affected germination and seedling length of hoary cress with fennel seeds having the highest inhibitory effect and reducing germination up to 34.9%. The water extracts in Petri dish essay had various effects, however the dry plant biomass in higher concentration reduced germination and seedlings growth for up to 100%. The applications of the extracts from fresh biomass in pots with soil differed from results in Petri dishes. Sage extract in higher concentration inhibited germination for 34.2%, and fennel extract reduced root length for 22.7%. The effect of incorporation of plant residues depended on the plant species and amount of the plant residues and was both stimulatory and inhibitory. The emergence reduction was the highest with incorporation of fresh rue residues.

Efficacy of Five Herbicides for Weed Control in Rain-Fed Lentil (Lens culinaris Medik.)

Lentil is vulnerable to weed competition because of its short stature, slow establishment, and limited vegetative growth. Although the vast majority of lentil production is under rain-fed conditions, there is a little published information on weed control with herbicides in rain-fed lentils. Field experiments were conducted to determine the efficacy of nine herbicide treatments including fomesafen, imazethapyr, linuron, pendimethalin, and pyridate alone or in combination compared with one or two hand weeding(s) on weed control and yield response in rain-fed lentil in Khorramabad, Iran in 2012 and 2013. Weed species included catchweed bedstraw, cowcockle, haresear mustard, hoary cress, wild mustard, and wild safflower. Total weed dry biomass in weedy check plots averaged 156 and 170 g m−2 in 2012 and 2013, respectively, and weed density and biomass were reduced in all treatments compared to the weedy check in both years. Plots that were hand weeded twice reduced weed biomass the greatest, whereas fomesafen, linuron, or one hand weeding did not control weeds satisfactorily. Noncontrolled weeds reduced lentil yield by 67% both years compared to the weed-free control. Lentil yield in 2013 (1,370 kg ha−1) was higher than in 2012 (1,150 kg ha−1). All herbicides tested injured lentil slightly, with pyridate (1,200 g ai ha−1) and pendimethalin (660 g ai ha−1 plus imazethapyr at 250 to 500 g ai ha−1) causing the least injury. Across all treatments, imazethapyr plus pendimethalin PRE, pyridate POST, and two hand-weeding treatments had the best performance for weed control and lentil yield.