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Vegetable IPM Updates Archive
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Weeds in Leaf Lettuce (November 12, 2014)
There are more than 50 broadleaf and grass weeds in this area that are common and have been here for a long time. We would like to have a herbicide that will control them all, not hurt the crop and be gone the day after harvest. We are a long way from achieving this. What we have done instead is to select for the weeds that escape
our weed control practices. Anything that shifts the advantage to the crop instead of the weeds will help. This includes herbicides, mechanical techniques and hand hoeing. Good weed control can be achieved using all three but may not be economical. Weed selection due to herbicide availability can currently be seen in leaf lettuce. Kerb, Prefar and Balan were the standard herbicides used in lettuce for the last 50 years. The postemergence grass herbicides were registered about 20 years ago but for broadleaf weeds there has been nothing new in half a century. To the contrary, with the loss of Kerb on leaf lettuce 5 years ago, there is less available on that crop than ever before. Prefar will control grass consistently, purslane and pigweed most of the time, lambsquarters and goosefoot some of the time and all of the other weeds never. Balan will control grass consistently and many of the small seeded broadleaves some of the time. Kerb will control the grasses and most of the broadleaves consistently including many that are not controlled by the other two such as shepardspurse, London rocket and wild mustard. The longer that Kerb is unavailable the more prevalent it will become.
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The Annoying Aphid

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