OCR Text |
Show Let's Control Alfalfa Weevil By George F. Knowlton Extension Entomologist Utah State Agricultural College The alfalfa weevil costs the Utah farmers several hundreds of thousands thou-sands of dollars each year. Many years the loss has exceeded $500,-000. $500,-000. Such losses can be very largely large-ly prevented. Alfalfa weevil control now is a relatively simple, profitable farm operation.- The efficient farmer watches his early growth. When the alfalfa shoots reach a height of l2 to 2 inches, the field is sprayed with 4 ounces of actual heptachlor or dieldrin per. acre. The amount of water used may vary from 6 to 50 gallons per acre, as desired. This means that 1 gallon of 25 per cent emulsified heptachlor should' treat about 8 acres; 1 gallon gal-lon of 18 per cent dieldrin should be used to treat 6 acres. In sea sons of army cutworm infestation, the grower does well to increase his dosage to 6 or 8 ounces of dieldrin, or not less than 10 ounces per acre of actual heptachlor. This should control adult alfalfa weevils, wee-vils, before they lay many eggs, and also clean up the cutworms, so that the alfalfa crop may grow normally.. Adult alfalfa weevils killed before be-fore they reach sexual maturity lay no eggs. If left to develop normally, each female weevil may deposit from 200 to 800 eggs. Usually Us-ually the infestation of alfalfa wee-vill wee-vill larvae appears during early May, to cause crop damage during last May and early June. (The infestation in-festation develops a few weeks earlier in "Utah's Dixie.") The most profitable way to pre- vent alfalfa weevil damage, with its loss of quality and reduced crop yield, is to destroy the adult weevils early. This prevents serious ser-ious outbreak. Control every season sea-son is profitable, when applied with careful timing and dosage, in areas of Utah where the weevil commonly causes crop losses. When alfalfa is grown for first crop seed, any additional weevil control needed, beyond the early spring stubble treatment, is care for when the crop is sprayed, in early bud' stage, using V2 pounds of actual DDT per acre. This treatment should always be applied ap-plied to the prospective seed crop for lygus bug control. If a dust is used instead of a spray, 20 pounds of 10 per cent DDT shoruld be applied per acre. Either treatment treat-ment controls alfalfa weevil larvae, lar-vae, lygus bugs, and reduces thrips populations. ... Forage Crop Protection Where alfalfa raised for forage (not seed) has been stubble sprayed, spray-ed, or where' the application was poorly timed, an insecticide treatment treat-ment may be necessary when forage for-age injury becomes obvious. Such a crop may be' treated with 1 ounce of heptachlor, 2 ounces of aldrin, 1 to 2 ounces of lindane, or 4 ounces of parathion per acre, i applied as a spray. Forage hay treated with heptachlor hep-tachlor may be cut within three days, but it , normally should be applied earlier than this before cutting time. Wait 15 days after treatment before cutting parathion, aldrin or lindane treated alfalfa. Do not feed DDT treated alfalfa to cows being milked, or the DDT will appear in the milk. Read and carefully follow the safety precautions printed on the insecticide container label. Use particular care to avoid poisoning of operator, other persons, or warm blooded animals when parathion spray or dust is handled and applied. ap-plied. ., If you desire further details of alfalfa weevil control under Utah conditions, secure a copy of Utah State Agricultural College Extension Exten-sion circular 213 from your local county agricultural agent. |