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(Bio) Weeds

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Joined: 06 Jul 2005
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Location: Angel C. de Dios

PostPosted: Sat Sep 02, 2006 7:21 am    Post subject: (Bio) Weeds Reply with quote

University of Chicago Press Journals
1 September 2006

Why are there so many weeds in your garden this year?

Some years, no matter how diligently you pull, your backyard garden is always covered with weeds. Other years, with the minimum of effort, your garden remains weed-free. What is the cause of these oscillations? A group of weed scientists based at the Spanish National Research Council (CSIC) spent fifteen years studying flixweed – a member of the mustard family commonly found in areas where the ground has been cultivated or disturbed – in an attempt to identify the processes underlying these fluctuations.

"The failure to recognize the intrinsic nature of many weed population changes may result in over-application of control inputs, with subsequent negative economic and environmental effects," says Jose Gonzalez-Andujar, who co-authored the study, forthcoming in The American Naturalist, with Cesar Fernandez-Quintanilla and Luis Navarrete.

Many populations exhibit cyclic oscillations. Everybody can recall a summer where mosquitoes hindered attempts at al fresco dining. These cycles can be produced by climatic conditions or by internal feedback mechanisms. However, in contrast with studies of insect and animal populations, little attention has been directed at the study of cycles in plants. What happens with your garden weeds?

The researchers demonstrate that there are some intrinsic mechanisms that explain observed plant oscillations – more specifically, evidence of cycles produced by delayed density dependence in a plant population growing under field conditions. This study can have a capital importance in crop protection.

"Traditionally, the major objective in weed management has centered on how weeds can be controlled. The emphasis on control, however, has obscured the overriding question of why weeds are so abundant at certain times and places," write the authors. "This is an ecological question that may lead to a better understanding of the agroecosystems and to the development of more sustainable agricultural systems."

Founded in 1867, The American Naturalist is one of the world's most renowned, peer-reviewed publications in ecology, evolution, and population and integrative biology research. AN emphasizes sophisticated methodologies and innovative theoretical syntheses--all in an effort to advance the knowledge of organic evolution and other broad biological principles.

J.L. Gonzalez-Andujar, C. Fernandez-Quintanilla, and L. Navarrete, "Population cycles in an annual plant produced by delayed density dependence." The American Naturalist 167:9.


American Phytopathological Society
1 September 2006

Fight weeds with plant pathogens

St. Paul, Minn. (September 1, 2006) -- Although plant pathogens are typically viewed as detrimental, plant pathologists with the American Phytopathological Society (APS) say plant pathogens may be a successful, eco-friendly tool for managing weeds.

"The use of plant pathogens to suppress weeds is considered as one of the alternative weed control options for areas or production systems where the use of chemical herbicides is not permitted or feasible," said Erin Rosskopf, USDA, Agricultural Research Service, Fort Pierce, FL. "Plant pathogens may also be used when the herbicide selection or usage must be rotated with other control methods in order to prevent the development of resistant weeds or lessen the impact of herbicides on the environment," she said.

Weed management is important due to the amount of damage weeds can cause to agricultural productivity. Weeds can reduce crop yields by as much as 12 percent (causing up to $32 billion in losses), based on the potential value of all U.S. crops of approximately $267 billion/year. Weeds also pose serious ecological problems. Invasive weeds are capable of altering ecosystem processes and displacing native plant and animal species. In addition, weeds serve as reservoirs for plant pathogens that impact crops.

According to Rosskopf, there are two approaches used for managing weeds with plant pathogens-the classical biological control approach and the bioherbicides approach. The classical biocontrol approach uses a pathogen imported from a foreign location to control a native or naturalized weed with minimal technological manipulations.

"Classical biological control using imported pathogens has an overall success rate of 57 percent and has been just as successful as the use of imported insects, with no instances of unexpected or undesirable effects," says Raghavan Charudattan, University of Florida, Gainesville, FL.

The bioherbicide approach utilizes native plant pathogens that are isolated from weeds and are grown to produce large numbers of infective propagules (such as spores). Infective propagules are applied at rates that will cause high levels of infection, which will greatly reduce the growth of, or kill the target weed before economic losses are incurred. Annual applications are required since the pathogen does not generally survive between growing seasons. It is estimated that there are more than 200 plant pathogens that have been or are under evaluation for their potential as bioherbicides.

More information is available in the first of a two-part series on using plant pathogens for weed biocontrol, located at
APS is a non-profit, professional scientific organization. The research of the organization's 5,000 worldwide members advances the understanding of the science of plant pathology and its application to plant health.


Questions to explore further this topic:

What are weeds?

What are the different types of weeds?

Identifying weeds

What are noxious weeds?

A list of invasive plants

Plant threats to Pacific ecosystems

Aquatic weeds

Images of weeds

Weeds in the Philippines

A Weed Management Handbook

Putting Weeds to Work

Are herbicides toxic?

Do herbicides have a lasting presence in the environment?

Biological Control of weeds

A National Strategy Invasive Plant Management (USA) (Australia)

Impact of Environmental Weeds on Biodiversity


Last edited by adedios on Sat Jan 27, 2007 3:43 pm; edited 2 times in total
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Joined: 06 Jul 2005
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PostPosted: Thu Sep 28, 2006 6:32 pm    Post subject: Cunning Weed Sniffs Out Victims Reply with quote

Cunning Weed Sniffs Out Victims

By Jeanna Bryner
LiveScience Staff Writer
posted: 28 September 2006
02:00 pm ET

It may look like a benign spaghetti noodle, but a bizarre parasitic plant has some cunning moves. When the stringy dodder plant emerges from the earth, it sniffs out a plant victim in the first known example of an amazing form of plant communication.

Then it sucks the life out of the other plant.

Considered an agricultural pest, the dodder relies solely on other plants to survive and infests a variety of crops, including tomatoes, carrots and alfalfa, earning it a spot on the U.S. Department of Agriculture’s Top Ten Weeds List.

Now, scientists from Pennsylvania Statue University have discovered the parasitic weed can sense airborne chemicals released by host plants and then steer in that direction. The finding, detailed in the Sept. 29 issue of the journal Science, shows for the first time that plants can "chatter" with one another, helping to resolve a decades-long debate about whether volatile chemicals are involved in plant-to-plant interactions.

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PostPosted: Mon Sep 24, 2007 12:45 pm    Post subject: Ragweed Research Is Nothing to Sneeze At Reply with quote

Ragweed Research Is Nothing to Sneeze At
Graduate Students Probe How Pesky Pollen Spreads
Under Varying Weather Conditions
Johns Hopkins University
24 September 2007

To a person with a pollen allergy, an 18-acre ragweed field sounds like a sneezy, red-eyed zone of misery. But to two environmental engineering researchers at Johns Hopkins, the parcel presented a rare and valuable opportunity to learn how the troublesome weeds grow, reproduce and scatter their pollen under varying weather conditions.

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