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Milk thistle (Silybum marianum) is cultivated as a medicinal plant but it also can be a troublesome weed. It is an annual or biennial herb that prefers high rainfall and fertile soils. Milk thistle has become a widespread weed in north-western Pakistan, where it causes yield reductions Յ37% in wheat and poses harvesting problems due to its thorny nature. Shortcomings in cultural practises, such as a low crop seed rate, wide row spacing, broadcast fertilizer, and limited crop rotation have contributed to milk thistle becoming a severe weed problem for farmers in this region.This paper reviews the biology of milk thistle and discusses the possible management options for its control, considering the socioeconomic conditions of farmers in Pakistan.

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to evaluate the effects of nitrogen (N) and sulfur (S) levels and their methods of application on quality parameters of canola . Four levels of S (0, 20, 40, and 60 kg ha −1 ) and three levels of N (80, 120, and 160 kg ha −1 ) and a control treatment (with both nutrients at zero level) were applied as a sole dose at sowing, in two split applications (half each at sowing and leaf rosette stages) and three split applications (one third each at sowing, leaf rosette stage, and early flowering). Large increases in oil and protein concentrations were measured at 40 kg S ha −1 while no further significant increase was observed at 60 kg S ha −1 . However, increasing level of S consistently increased glucosinolate concentrations to the highest level of 60 kg S ha −1 . Nitrogen significantly increased protein concentrations up to the maximum level of 160 kg N ha −1 while glucosinolate concentrations were increased up to 120 kg N ha −1 . However, oil concentrations showed negative trend to increasing level of N.

Two common problems in soybean [Glycine max (L.) Merr.] fields are weeds and incomplete crop plant stands, and these problems may interact in their influence on soybean yield. A study was conducted in 1986 and 1987 to examine whether weed interference was influenced by soybean plant stand and planting pattern. In full stands (26 plants/m row) of soybean, common cocklebur (Xanthium strumarium L.) and velvetleaf (Abutilon theophrasti Medic.) spaced 1.5 m apart in the row decreased soybean yields 29 and 34%, respectively, in 1986 and 19 and 15%, respectively, in 1987. Decreasing the soybean stand 20, 40, and 60% without weeds resulted in yield losses of 8, 18, and 34% (across both years) in evenly spaced soybean plants, while similar stand losses caused by removal of sections of row resulted in yield losses of 14, 28, and 35%, across both years, respectively. When common cocklebur and velvetleaf were present, percentage yield decreases due to stand losses were similar to those in the weedfree treatment; there was no interaction between weed treatment and stand loss treatments. Light interception by the canopy, measured only in 1987, was higher in weedy plots than in weedfree plots, with the additional interception presumably due to the weeds. Common cocklebur produced more dry weight than did velvetleaf, but the two weeds had similar effects on soybean yield. These results indicate that, while weed competition and stand loss can both cause substantial yield losses in soybean, the effect of these factors is additive when both occur in the same field, and weed growth is not greatly enhanced by decreased competition resulting from loss of soybean stand.

A total of 16 different allergenic and invasive weed species belonging to 12 different families collected from different areas of study area. Among the studied plants, most of the species belong to the Asteraceae family. For morphological studies of pollen through LM and SEM the samples were acetalized. We done the fieldwork for the collection of weed plants and also performed the experimental work i.e. SEM and LM for the pollen morphology. Most of the species recorded with pollen of tricolporate and echinate. Species belonging to Asteraceae were considered as most abundant and allergenic as compared to others. The maximum polar diameter was noted in the Convolvulus arvensis is 40.00 µm and the minimum were noted in Oxalis corniculata is 6.15 µm. Maximum exine thickness was noted in convolvulus arvensis is 3.70 µm and Minimum were noted in Sorghum halepense is 1.65 µm. It was noticed that most of the allergenic and invasive weeds found in plain areas of Lakki Marwat during September and April. Present study provides information about the allergenic and invasive weeds plants and their threats to biodiversity. The pollen of such weed plants causes asthma and atopy disease in humans.

Common cocklebur is a new weed in irrigated maize grown for forage in the hot, dry region of northwest Pakistan. We conducted experiments in the Khyber Pakhtunkhwa Province, Peshawar, Pakistan, during 2006 and 2007 to evaluate the interaction of common cocklebur density and maize density on biomass, leaf area index (LAI), and plant height of forage maize. Seven common cocklebur densities (0, 2, 4, 6, 8, 10, and 12 plants m−2) in maize planted at four densities (5, 7.5, 10, and 12.5 plants m−2) were evaluated. An ANOVA for both years revealed significant main effects and interactions for all variables. Regression of measured variables against common cocklebur density showed that maize biomass declined linearly as common cocklebur density increased from 0 to 12 plants m−2, with an increasing rate of decline for high maize densities and low maize densities. Combined data for all maize densities revealed that the relationship between maize biomass and common cocklebur biomass fit a linear function, with 1.28 to 1.35 kg ha−1loss in maize biomass for each kilogram per hectare increase in common cocklebur biomass from about 1,500 to 3,200 kg ha−1. Above 8 to 10 common cocklebur plants m−2, weed biomass declined, presumably due to intraspecific competition. An increase in common cocklebur density decreased maize LAI about 0.15 to 0.3 units for each additional common cocklebur plant per square meter in 2006, and 0.11 to 0.24 units in 2007. Common cocklebur LAI increased in a linear fashion as density of the weed increased. Results suggest that the effect of common cocklebur interference on maize biomass was associated with a change in allocation of resources, resulting in increased crop height growth at the expense of a reduction in LAI and presumably potential light interception by the crop as common cocklebur density increased.