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Show Alfalfa Weevil Control... i By George F. Knowlton Utah State Agricultural College Extension Entomologist The alfalfa weevil has cost Utah hay and alfalfa seed growers many millions of dollars in crop losses over the years. This began in 1904 when the weevil was first found near Salt Lake City. Now this is a pest over most of the west. It recently has also caused serious crop injury in some eastern areas of the Nation. . Insects cause a loss of from $7,000,000 to well over $10,000,000 to Utah crops and livestock each year. The alfalfa weevil annually would cause injury ranging from approximately $300,000 to $1,000,-000, $1,000,-000, if not controlled. Research on alfalfa weevil control, con-trol, conducted largely by F. V. Lieberman, , U. S. Department of Agriculture Entomologist, located at the Utah State Agricultural College, Agricultural Experiment Station, has to a large extent made possible the elimination of alfalfa weevil losses. During the several seasons since the development develop-ment of the new spring stubble-treatment stubble-treatment to kill adult weevils, estimated crop savings of y2 million mil-lion dollars to nearly 1 million dollars have been achieved by our Utah farmers. Control the alfalfa weevil in early spring. Do this by means of a heptachlor or dieldrin stubble spray, Mr. Lieberman and other Utah State Agricutural College entomologists advise. This involves applying 4 ounces of actual heptachlor hep-tachlor or dieldrin per acre. To be most beneficial this spray should go on when alfalfa first growth is only V2 to 2 inches high. This occurs fairly early, we must remember. This early spring treatment is aimed at destroying the overwintering overwin-tering alfalfa weevils before the females lay their eggs. Only a few female weevils mature sexually sex-ually and lay any eggs in the fall. This early spring treatment makes for better quality and more alfalfa, al-falfa, for larger alfalfa seed crops, and makes it unnecessary to have an insecticide residue present on first crop alfalfa when it is cut for hay. To secure most effective and . profitable alfalfa weevil control, let's remember a few special points. 1. Whether alfalfa is grown for hay or seed, the best way to control con-trol the alfalfa weevil with an insecticide in-secticide is to apply a spray when the first spring growth is to 2 inches long. This usually is between be-tween March 5 and April 15. 2. Use 4 i ounces of heptachlor or 4 ounces of actual dieldrin in at least 6 gallons of water, per acre. 3. This kills most of the adult weevils before they lay many eggs. It thus prevents the development develop-ment of enough larvae to damage the crop later. When first crop alfalfa seed is to be grown, any necessary additional ad-ditional weevil control is provided provid-ed by the application of DDT for control of lygus bugs. This application appli-cation should be made when ' the plants are in the early bud stage. The recommended dosages are 1.5 pounds of actual DDT per acre applied as a spray or at least 20 pounds of 10 DDT applied as dust. When first-crop hay is raised, some growers may desire to control con-trol the alfalfa weevil by killing the larvae after they become a-bundant, a-bundant, in late May or early June. For maximum benefit, this treatment should be made before most of the plants have started to turn grey. Spray or dust with to 1 ounce of heptachlor or 1 to 2 pounds of actual methoxy-chlor, methoxy-chlor, 4 ounces of parathion, 2 ounces of aldrin, or 1 to 2 ounces of lindane. If parathion is used, it should be applied with power machines only and in strict observance ob-servance of the directions and warnings of the manufacturer. This control is not considered to equal, in benefits, the spring stubble spray. Wait 3 days before harvesting heptachlor-treated hay. Wait 15 days after treatment before cutting cut-ting hays treated with parathion, aldrin or lindane. Do not feed alfalfa al-falfa from crops treated with DDT to dairy animals being milked, to animals being fattened for slaughter slaugh-ter or to poultry. When heptachlor, hepta-chlor, chlordane, orlieldrin is applied ap-plied for early-seasons control of alfalfa weevil adults, it is best not to allow dairy animals being milked to graze on the alfalfa until after the first cutting. |