August 2005

Pesticide Potpourri

  • wpdoc13.gifAphids salivate at the thought of beans! In fact, if it weren't for their saliva they would starve to death. Bean plants contain contractile protein bodies (forisomes) which change their shape in response to calcium (released during stress). In reaction to wounding, forisomes block the sieve plates (structures in the stems which regulate fluid transport) by changing their shape and acting as a 'plug'. The dispersion of the forisome protein prevents fluids from leaking out of the plant (otherwise your plants would 'bleed' to death when you mow your lawn). Aphids overcome this blockage by injecting their saliva into the plant. The reaction of the aphids to the change in fluid flow was investigated with the use of an electrical circuit. When plugging occurred at the sieve plates, feeding aphids reacted by producing more saliva. (Society for Experimental Biology, 7/13/05).
  • wpdoc14.gifScientists at Washington State University in Pullman have discovered a molecule that plays a role in the battle plants must win against bacteria and fungi. The group isolated a small protein called Pep1 that appears to act like a hormone, signaling the rest of the plant to raise its defenses at the first sign of an infection. They also discovered the receptor protein which binds Pep1 to exert its protective effects. Pep1 was isolated from the plant Arabidopsis thaliana, but the same molecule is found in crop species such as canola, soybean, potato, tomato, rice, and poplar. Therefore, further work on Pep1 and its receptor could lead to a general increase in the resistance of crops to pathogens, which could greatly benefit farmers. Already, the researchers have used the Pep1 gene to increase the resistance of Arabidopsis plants to the fungal pathogen Pythium irregulare. (American Society of Plant Biologists, 7/19/05).
  • wpdoc15.gifThe California Department of Food and Agriculture announced in July that a majority of California's wine grape growers have voted to continue paying assessments through March 2011 to find a cure or treatment for a deadly grapevine pest. With more than 4,000 growers voting, 89 percent favored a new round of assessments that have raised a total of $17.8 million for research into Pierce's disease over the past four years. This year, growers are being assessed $2 for each $1,000 in grapes sold for crushing to pay for the research program. The assessment varies each year from $1 to $3 per $1,000 of grapes sold. (The Sacramento Bee, 7/26/05).
  • Ghana has taken a questionable stance against the receipt of genetically modified (GM) foods. The Food and Agriculture Minister was cited as saying the country would reject, without hesitation, the importation of any GM foods, crops and materials into the country although it might solve the famine problems being experienced, especially in the northern part. (The Ghanaian Chronicle, 7/28/05).
  • wpdoc16.gifThe United Kingdom’s Department for Environment, Food, and Rural Affairs has released “The Potential For Dispersal Of Herbicide Tolerance Genes From Genetically-Modified, Herbicide-Tolerant Oilseed Rape Crops To Wild Relatives.” In the study, researchers assessed the transfer of herbicide tolerance both in the field and in the laboratory, on a total of 95,459 seedlings of wild relatives of herbicide tolerant oilseed rape (canola). Plants were tested by application of a small quantity of glufosinate ammonium to individual leaves, and observing whether any necrosis resulted. Any plants showing signs of tolerance to the herbicide were subjected to polymerase chain reaction (PCR) to identify whether the gene was present. A single plant of Sinapis arvensis showed no reaction to the application, and a leaf of this plant was taken for PCR analysis. Researchers found that the gene construct was present in the leaf sample. Since only one plant showed resistance to treatment, researchers stated that they did not see the transfer of herbicide tolerance to wild relatives as a major problem, and that the risks of such a phenomenon were “minimal.” They also estimated the incidence to be very low, since no other examples of resistance to herbicide treatment were found in other samples in the study, or in other samples in studies conducted elsewhere (e.g. in France, where over 2 million seeds of wild relatives were tested). (Crop Biotech Update, 7/29/05).
  • wpdoc17.gifPlant Management Network recently published a paper that summarized organic fungicide trials in tomato. The Ohio State tests examined a number of organic products or product combinations. Among the items tested were horsetail (Equisetum arvense) extract, Bordeaux mixture, copper hydroxide, garlic extract, humic acid, potassium carbonate, hydrogen dioxide (Oxidate®), Bacillus subtilis strain QST 71113 (Serenade®), Bacillus pumilis strain QST 2808 (Sonata®), seaweed cream, tea tree (Melaleuca alternifolia) oil, and neem oil. The main disease pressures were early blight (Alternaria solani) and Septoria leaf spot. Interestingly, in the first year of the study, many of the treatments actually increased the incidence of early blight in a year in which disease pressure was light. In the subsequent year (2003), disease pressure was more intense. Although none of the treatments increased yield significantly compared to the water control, Sonata®, tea tree oil, and horsetail extract treated plots yielded between 35 and 45 percent more tomatoes. It was also demonstrated (again) that copper reduces leaf diseases. (Plant Management Network, 7/13/05).
  • wpdoc18.gifIn early August, the UN’s Food and Agricultural Organization (FAO) warned that Iraq's seed industry has collapsed and the country is currently not able to meet farmers' needs for improved crop varieties. High-quality seed is one of the most critical inputs for sustainable agricultural production. FAO has launched an appeal for a $5.4 million project to rebuild the national seed industry. Iraq had a relatively stable and functioning public- sector controlled seed industry before the war in 2003. After the war, research and seed production facilities have greatly deteriorated. Agricultural research centers were devastated and most of the equipment and machinery, including seed processing facilities and seed stocks, were looted or damaged. As a result, Iraq can only cover four percent of the national demand for quality seeds from its own resources. Most seeds come from farmers' own seed reserves, which are of low quality. (FAO Release, 8/8/05).

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