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Show Weevil Control Methods Outlined; Fanners Advised onEarly Prevention (By George F. Knowlton, Extension Exten-sion Entomologist, Utah -State Agricultural College The alfalfa weevil is a serious pest in Utah practically every year. Damage was somewhat less serious in 1952 than most seasons, sea-sons, due to the very rapid growth of the crop which occurred oc-curred after the high spring water wa-ter receded and permitted the crop to grow. However. 'in 1951 the weevil caused great damage In most areas where early spring control had been neglected. The new alfalfa weevil control con-trol program, developed by USDA entomologist F. V. Lieberman and his associates at the Utah Agricultural Experiment Station, ami entomologists working In Montana and other western states, has proven that this pest can be controlled economically by destroying the overwintered adult weevils. Control, however, must be accomplished before the female weevils lay many eg,'s Otherwise the eggs will hatch and become worms to feed on alfalfa foliage during June and early July. A new insecticide called hep-tachlor hep-tachlor will enter the alfalfa weevil control picture in Utah and much of the northwest, this season. Research oy entomologist entomolo-gist Lieberman and his associates associ-ates at the Legume Seed Research Re-search laboratory showed this i I i i : incn ...l. (.nt-lIllLrfl uuiuig nnvn ap plied at the rate of four ounces actual heptachlor per acre as a spray, to give control equal to any other insecticide tested for the early spring weevil control treatment. Ordinarily an insecticide insecti-cide Is not recommended for control con-trol use on the basis of one year's research data, no matter how favorable. However, because extensive ex-tensive research in Montana, Colorado and Idaho last season yielded control results almost identical with those secured in Utah, the Utah entomologists decided de-cided to place a tentative recommendation recom-mendation for use of heptachlor for 1953. The widespread geographical geo-graphical area of experimental tests last season helped to quite an extent to prove its use under varied climatic conditions, such as might have been encountered in a single area through control tests made over several seasons. In 1952 great amounts of dlel-drln, dlel-drln, as well as chloidane, were sprayed on N alfalfa in early lent weevil control in practically practical-ly all cases. Control chemicals were adequate in supply for all Utah needs in 1952. They should again be adequate to meet all 1953 weevil control needs. Possibly a little information on the seasonal history of the alfalfa al-falfa weevil will help us to understand un-derstand the control problems: Adult weevils emerge from cocoons co-coons in the fields from May 'to August. Most of the emerged weevils survive on through the next winter. Some females deposit de-posit a few eggs in the fall. Many more eggs are laid during dur-ing the following spring. At first eggs are laid only in small fragments frag-ments of dead alfalfa and grass stems. However, after the spring alfalfa growth becomes six inches inch-es tall, more and more eggs are laid in growing alfalfa stems. Each female weevil deposits from 200 to 800 eggs. Only small numbers of larvae hatch before be-fore May 1. Larvoe becomes dam-agingly dam-agingly abundant during late May and early June. Each Larvae Lar-vae molts three times before spinning its netlike cocoon among leaves on or near the surface of the ground. Pupation occurs in this cocoon. The early spring treatment doen't destroy the eggs, nor the worms, after they are hatched out. It is aimed to kill the adults. We must do this before eggs are laid. You might call this "preventive "pre-ventive insect control". Could anything be better than to pre- vent worm damage to first crop, avoid any growth delay between first crop being cut and the new growth appearing on second crop? This keeps the quality of alfalfa "tops" and that counts as much as tonnage in a hay crop. |