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Herbicide Bleach


Herbicides Photosynthesis Inhibitors

In a Nutshell

  • Blotches of yellowing tissue between leaf veins.
  • Yellowing of leaf margins at later stage.
  • Leaf veins remain green.
  • Bleached appearance.
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Leaves develop interveinal chlorosis or mottling, turning the tissue between veins yellow. During later stages, the leaf margins become yellow while the leaf veins remain green. Gradually, leaves dry up and may drop within two to five days, giving them a 'paper bag'-like appearance.

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The symptoms depend on the product used, dosage and time of application. The damage is caused by group C herbicides, such as atrazine, bromoxynil, diuron, and fluometuron. Due to their rapid and harmful effect on leaves, they are often qualified as 'bleachers'. They block photosynthesis and destroy the green pigments contained in the cells, discolouring them. Older leaves are more affected than younger leaves. Symptoms develop most rapidly in full sunlight. Problems with development of resistance are common in several types of weeds (grasses, mustard, stinging nettle and wild radish, for example).

Organic Control

There are no biological control solutions for the damage. Prevention and good farming practices are the keys to avoiding harm in the first place.

Chemical Control

Always consider an integrated approach with preventive measures and biological treatments, if available. Before planning a herbicide spray, be sure that you know the type of weed you are dealing with (basically broadleaf weeds vs grasses) and choose the best. Carefully select the herbicide, by reading the label carefully and following dosage instructions, as indicated.

Preventive Measures

  • Be sure to know the type of weed you are dealing with (basically broadleaf weeds or grasses).
  • Carefully select the herbicide that best fits your purpose.
  • Read the label carefully and follow dosage instructions, as indicated.
  • Always clean the spray container after use to avoid contamination with a different herbicide.
  • Avoid spraying in windy conditions to prevent drift to other fields.
  • Use drift reducing spray nozzles that target weeds better.
  • Try and test the herbicide in pastures and hayfields to monitor results.
  • Check weather forecast carefully and do not spray while rain or direct exposure to sunlight.
  • Maintain proper record of activities with application dates, products, field locations and weather conditions.

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