April's Ag Advice by April Borders As our crops start to grow and emerge we need to be out in our fields scouting and checking for diseases and insects. Because of the cooler temperatures the plants are growing slower and their root growth is poor. This is leading to pale plants as nitrogen uptake is very slow. As warmer temperatures start we will see these plants start to green up and grow better.
We are also seeing some purple corn and in some cases it is extremely purple. As with nitrogen, when plant root growth is slow because of the cooler temperatures, the root uptake of phosphorus is slow. The immobile nutrients are affected even more than the mobile nutrients are. Again as temperatures warm, the purple plants will turn green again. However, if they don't and they stay purple into the four to five leaf stage, then a soil test should be done to make sure that levels are adequate for growth.
Cutworms are now starting to cause widespread damage to corn seedlings so you need to be out scouting your fields. SDSU Extension Entomologist Mike Catangui has found black cutworms infestations in fields in southeast South Dakota. The larvae of the black cutworms can be very damaging because they cut the corn growing points from under the soil. Wilted seedlings, scattered pieces of leaves, and small holes on leaves are common signs of black cutworm infestations.
Cutworms are active at night and hide under loose soil during the day. Scouting during the day involves scratching the soil surface to expose hidden larvae. Producers should consider insecticide treatment if 5 percent (one in 20) of the seedlings show signs of cutting or leaf feeding, and if the larvae are still less than an inch long. Insecticides labeled for use against cutworm larvae on corn as seedling foliar sprays include Asana XL, Baythroid, Capture 2EC, Lorsban 4E, Mustang 1.5EW, Pounce 3.2EC and Warrior. Read and follow all directions on the label.
Winter wheat should be inspected for signs of stripe rust. Even though we are not a big wheat producing county, this is still a plant disease that we need to watch for. Stripe rusts can move quickly. It has a shorter regeneration time than leaf rust. In 10 days, the stripe rust situations can deteriorate dramatically, so watch fields with stripe rust closely. SDSU Extension Plant Pathologist Marty Draper says that fungicide treatments are effective against stripe rust, but early treatment is critical. Stripe rust can be treated with fungicides such as Tilt, Quadris and Folicur.
Folicur has received a special label for 2003 allowing its use for the suppression of Fusarium head blight (scab) in wheat, but at the same time it will also provide protection against leaf diseases. If the crop is in the heading stage, Folicur is the best choice for treatment as some fungicides cannot be applied after head emergence or have long preharvest intervals. Draper cautions that the cost of treating the disease may outweigh the benefits unless a producer sees the potential for reaping yields of at least 40 bushels an acre.
As the season progresses we will try to keep you up-to-date on disease and insect problems as we receive notification of them. If you have questions and concerns or have problems in your fields please call the Extension office, this allows us to help you make timely production decisions. For more information call the Extension Office at 677-7111.