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"Weeds History."
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Promotion of weed species diversity and reduction of weed seedbanks with conservation tillage and crop rotation
In a 6-yr study on four farms (36 fields) in Ontario, Canada, we tested the effects of tillage (moldboard, chisel plow, no tillage) and crop rotations (continuous corn, corn-soybean, corn-soybean-winter wheat) on emerged and seedbank weed species diversity and density. Aside from the imposed experimental treatments, all other management was generally consistent among farms. Tillage had the largest effect on weed diversity and density. No tillage promoted the highest weed species diversity, chisel plow was intermediate, and moldboard plow resulted in the lowest species diversity. These results are consistent with ecological succession theory. The increase in weed species diversity resulted from 20 species being associated with no tillage systems, 15 of which were winter annuals, biennials, or perennials. Emerged weed density was affected only by tillage. Over 6 yr, seedbank declined in no-tillage systems from 41,000 to 8,000 seeds m−3. Crop yields were not affected by tillage or crop rotation. In practical terms, reduced tillage in combination with a good crop rotation may reduce weed density and expenditures on weed management. Nomenclature: Glyphosate; corn, Zea mays L. ‘Pioneer 3902’; soybean, Glycine max (L.) Merr. ‘KG 40’; winter wheat Triticum aestivum L.
Journal Article
The first weed management textbook in the United States (part 2)
This article overviews the earliest weed management book published in the United States. The most problematic weeds of that era are named, along with suggestions for their control.
Journal Article
When does it make sense to target the weed seed bank?
Weed seeds initiate most weed invasions of arable fields, yet there is relatively little information on the value of managing weed seed banks. Matrix population models were used to examine the relative importance of managing weed seed banks, in relation to other life stages, for four model weed species with varying life histories. Simulations for giant foxtail and common lambsquarters, summer annual weeds of arable fields; garlic mustard, an obligate biennial invasive weed of temperate forests; and Canada thistle, a perennial weed of pastures and arable fields, were run under conditions of varying population density and efficacy of seedling control. The models were subjected to elasticity analysis to determine what happened to weed populations when different life stages were targeted. Losses from the dormant seed bank were most important for summer annual weeds, of intermediate importance for biennial weeds, and of low importance for perennial weeds. More effort is needed to develop weed seed-bank management techniques for summer annual weed species as part of integrated weed management systems.
Journal Article
The history, distribution and rate of spread of the invasive alien plant, bridal creeper, Asparagus asparagoides (L.) Wight, as determined from a questionnaire survey of landholders in south-western Australia
The distribution and rate of spread of the introduced weed bridal creeper, Asparagus asparagoides (L.) Wight, were calculated from the results of a questionnaire that was distributed to landholders in the south-west of Western Australia. The weed was associated with regions that receive more than 350 mm of annual rainfall. There was a weak association between properties that had a longer history of disturbance through clearing of native vegetation and the presence of A. asparagoides. On a local scale, the questionnaire indicated that the rate of spread of A. asparagoides peaked at 0.6 m/yr of radial spread for patches of 10m2. The rate of spread of A. asparagoides on a regional scale was calculated as 0.09 postcode regions per year. While 50% of respondents indicated that they attempted to control the weed, only 20% of land managers on neighbouring properties (usually roadside reserves) were involved in some type of weed control. The level of weed control also influenced rates of spread calculated for weed patches for the two groups. Asparagus asparagoides was not ranked highly as a weed by landholders, whereas government officials surveyed considered it the most important environmental weed.
Journal Article
Alien plant species with a wider global distribution are better able to capitalize on increased resource availability
• A high ability of alien plant species to capitalize on increases in resource availability has been suggested as an explanation for being globally successful. Here, we tested this hypothesis meta‐analytically using existing data from experiments manipulating plant resources (light, water and nutrients). • From these studies we extracted the response to resource increase of biomass, as an indicator of plant performance, and the responses of two traits related to resource capture: root : shoot ratio and specific leaf area (SLA). For 211 species recorded in the Global Compendium of Weeds, we assessed the relationship between effect sizes from such studies and the number of global regions where a species was established. • We found that globally widespread species exhibited greater biomass responses to increases in resources overall, compared to less widespread species. Root : shoot ratio and SLA responses to increased resource availability were not related to species global distribution. • In general, globally widespread alien plant species were better able to capitalize on increased availability of resources, through achieving increased growth and biomass accumulation, while greater plasticity of key resource‐capture traits per se did not appear to be related to greater success.
Journal Article
The Origin of Cultivation and Proto-Weeds, Long Before Neolithic Farming
Weeds are currently present in a wide range of ecosystems worldwide. Although the beginning of their evolution is largely unknown, researchers assumed that they developed in tandem with cultivation since the appearance of agricultural habitats some 12,000 years ago. These rapidly-evolving plants invaded the human disturbed areas and thrived in the new habitat. Here we present unprecedented new findings of the presence of \"proto-weeds\" and small-scale trial cultivation in Ohalo II, a 23,000-year-old hunter-gatherers' sedentary camp on the shore of the Sea of Galilee, Israel. We examined the plant remains retrieved from the site (ca. 150,000 specimens), placing particular emphasis on the search for evidence of plant cultivation by Ohalo II people and the presence of weed species. The archaeobotanically-rich plant assemblage demonstrates extensive human gathering of over 140 plant species and food preparation by grinding wild wheat and barley. Among these, we identified 13 well-known current weeds mixed with numerous seeds of wild emmer, barley, and oat. This collection provides the earliest evidence of a human-disturbed environment-at least 11 millennia before the onset of agriculture-that provided the conditions for the development of \"proto-weeds\", a prerequisite for weed evolution. Finally, we suggest that their presence indicates the earliest, small-scale attempt to cultivate wild cereals seen in the archaeological record.
Journal Article
The Role of Ground Beetles (Coleoptera: Carabidae) in Weed Seed Consumption: A Review
Weed management is a challenge in all agroecosystems. Given the negative consequences associated with herbicide-based weed management, it is important to consider integrated weed management options with emphasis on strategies such as biological control. Postdispersal weed seed predation by granivorous and omnivorous carabid beetles results in substantial natural suppression of weed populations. Although the role of ground beetles as “generalist predators” in various agroecosystems is known, their contribution to weed management is not well recognized. In this context, this review presents an account of carabids and their granivorous nature, the importance of a seed diet in the life histories of different carabid groups, factors affecting granivory, and their potential role in weed seed management. Below, we discuss the interrelationships among various factors influencing weed seed consumption by carabids, its consequences for weed management, and the need for future research.
Journal Article