A2B-Lancaster Farming, Saturday, May 17,1986 Activity In Alfalfa BY JOANNE WHALEN Extension Pest Management Specialist University of Delaware Timely management of crop pests can help growers maximize profits. Throughout the growing season, I’ll be reporting on currept insect, disease and weed pests producers in Delaware and neighboring states should be scouting for. I’ll have suggestions from myself and other extension specialists on scouting techniques and control options for these pests. This time, I’m going to talk about the potential for pest problems in alfalfa. When it comes to alfalfa diseases, be sure to look for Sclerotinia crown and stem rot in fall-seeded alfalfa fields. During the past couple of weeks, I’ve seen Sclerotinia infections cause the complete loss of two fall-seeded fields. Delaware’s extension plant pathologist Bob Mulrooney tells me that this fungus attacks new seedlings in the fall and over winters in infected plants. 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As the food supply is exhausted or the weather turns hot and dry, this fungus produces hard black bodies called Sclerotia which may be found on or in the stems and crown. Mulrooney says the only way to control this disease is to avoid contact with the fungus. He recommends: (1) avoiding fall seeding on sites where the fungus was present the previous spring, (2) a three to four year rotation between forage legumes if spring symptoms are present, and (3) deep plowing to bury the fungus source. While scouting for diseases, be sure to check for alfalfa weevils and pea aphids. The alfalfa weevil is the major insect pest attacking the first cutting. Both yield and quality can be reduced by weevil feeding, so early detection is necessary to prevent economic DISTRIBUTOR H.C. 64 - Box 93 ONEONTA, N.Y. 13820 losses. Larval feeding generally begins shortly after plant growth starts in the spring. Damage initially ap pears as small pinholes in newly opened leaves. As the larvae mature, these feeding holes enlarge and leaves appear shredded and skeletonized. Heavily infested fields may look gray. Start checking for alfalfa weevil larvae in mid-April and continue on a weekly basis until the first crop is harvested. Recent scouting reports indicate that weevil populations are higher than last year. However, if we get favorable growing conditions over the next few weeks, the alfalfa could stay one step ahead of the weevil. Base treatment decisions on a random sample of 30 stems collected in an M-pattern throughout the field. Place stems Model 1850 FEATURES: • Zero Turning Radius • Joystick Control • Electric Lift and Clutch • 18 HP Engine • 24 HP Wheel Motors Phone 607/432-0891 in a bucket and beat them against the inside to dislodge larvae. In general, we recommend an in secticide treatment if you find two or more larvae per stem. Remember, long residual materials such as Lorsban, Guthion, or Furadah should be used when economic population levels are found early in the season. As we approach the first cutting, short residual materials such as Malathion and Imidan should be used. Growers often ask if they should cut or spray their alfalfa when they find a threshold level of weevils. In general, if the crop is in the full bud , stage and a threshold level is reached, we recommend har vesting the field instead of spraying. However, if the population level is steady and you cannot harvest in the next three to five days, apply a short residual Of Standing Timber Specializing in: Oak ( Ash, Poplar, Walnut and Other Hardwoods No Job Too Small, No Tree Too Big. Will Also Do Custom Chain Sawing * Clearing Small Acreage * Topping and Removing Trees * * Firewood Cutting, Etc. 8 Years of Professional Exj KUHN QYROSTAR QRS 29 Raka/ Taddar A great raka... and ... a great taddar. Two machinaa in ona! 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We recommend an insecticide treatment if you find 50 to 75 aphids per sweep. Delaware residents who want further information on in-season crop pest activity can call the University of Delaware Cooperative Extension Service’s CROP PEST HOTLINE at 1-800- 345-7544. Out-of-state residents can call 1-302-451-8851. JIM RUTT BUYER Will Give Free Appraisals And Will Also Bid. 717-367-7831 Wall Dona! isags! jolnlnfl ® i6 q years lechnolofly »or o ★ Insured rience ' ft * g*W»f '
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