Soybean aphids still a threat Soybean aphids are repopulating some soybean fields in the area to the point they need a second insecticide application. Remember, soybean aphids can double their population every 2-3 days. If even a few aphids survive the insecticide application, three weeks later fields can be at or beyond the economic threshold again. At this stage of the growing season, growers need to pay attention to the section on the label regarding information on pre-harvest interval. This is the minimum time that must pass between treatment and harvest. Warrior has a 45-day pre-harvest interval, so growers will need to consider other products such as Asana, Lorsban, Mustang or Furadan that all have 21-28 day pre-harvest intervals. According to our soybean agronomist at the U of M, Seth Naeve, as of Aug. 14 only 10 percent of the yield had formed, meaning seeds had accumulated only 10 percent of their dry matter. High populations of aphids feeding on pods and petioles could most likely reduce yields, so growers need to continue scouting their fields through Sept. 1 for full-season types. It wouldn’t surprise me if we see fewer soybeans grown next year due to the extra cost of the insecticide applications. For more information on soybean aphids, go to the Web site www.soybeans.umn.edu/home.htm. Cyanide kills cedar waxwings I had a couple of calls this spring from homeowners who found groups of dead cedar waxwings in their yards. Evidently, this was quite a problem in South Dakota too. A veterinarian pathologist there found that the birds had high levels of hydrogen cyanide, also called prussic acid. This product is released in certain plants when they are crushed, wilted, frozen or eaten during periods of regrowth. Evidently birds had eaten Cotoneaster lucidus and crab apples. In recent weeks, I have had calls from homeowners who have dead birds in their yards. I’m sure some birds such as blue jays and crows have the West Nile Virus. The Minnesota Department of Health is no longer interested in having birds sent in for testing, so it’s not necessary to call our office. Renovating lawns Fall is a great time to renovate lawns. Weeds are less competitive and temperatures are cooler so seeding can be done to fill in patches. Use a combination of Kentucky bluegrass and creeping red fescue seed at 3-4 pounds per 1,000 square feet. September is the best time to spray dandelions. All perennial weeds are loading up on carbohydrates in fall to carry them through the winter months. Spraying with 2,4-D products such as Weed B Gone will knock out nearly all dandelion plants in the lawn. Power raking can also be done in early September to stimulate new root growth and remove dead roots. If your lawn feels spongy, it’s a good bet dead roots are building up and need to be removed. Fertilizing the lawn soon after it has been power raked will bring any lawn back to life.
