For soybean, a general guideline is that if stippling reaches mid-canopy leaves, a treatment is likely necessary. For corn, the goal is simply to keep damage from reaching the ear leaf; treat when the lower one-fourth to one-third of the canopy shows damage and mites can be seen in the middle third of the canopy.
Spider mites live on the undersides of leaves and are more concentrated lower on the plant. If you decide to spray, canopy penetration is critical. Do not skimp on water—for ground applications, use 20 or more gallons per acre; for aerial applications, use 3 to 5 gallons. Evaluate control three to five days after spraying.
If you've decided that an infestation warrants spraying, don't hold up a spray waiting for rain. Instead, if rain is unlikely to occur before the spray dries, go ahead with the spray. Reducing spider mite pressure will allow the crop to take full advantage of any moisture from the rain.
If your field is infested with both spider mites and soybean aphids, base the treatment decision on the worst problem.
Prepare for higher forage prices
At the July 24 hay auction in Pipestone, supreme quality alfalfa hay brought a high of $260 per ton, while grass/alfalfa mixed hay brought a high of $200 per ton, reports Krishona Martinson, crops educator and equine specialist, U-Minnesota Extension. Grass hay was slightly lower at $180 per ton.
To prepare for higher prices, livestock owners should consider these tips:
•Keep in mind that quality forage should be the backbone of the livestock diet. For cattle producers, corn silage, alfalfa or grass haylage, and straw can be added to the diet. However, the drought has affected the supply and price of these feedstuffs as well. For horse owners, forage (in the form of hay or pasture) should comprise a minimum of two-thirds of their diet. Few forage alternatives exist for horses.
•If purchasing drought-stressed forage (hay products or corn silage), the forage should be tested for nitrates. Nitrates can accumulate in stems and stalks of drought-stressed plants. Once livestock consume the forage, nitrates turn into nitrites, which bind to red blood cells, preventing the cells from carrying oxygen to tissues. Two cases of nitrate toxicity have recently been reported in Wisconsin cattle herds. On a positive note, drought-affected alfalfa usually has a higher leaf/stem ration, resulting in better quality.
•If possible, consider adding hay storage to reduce the effects of seasonal price fluctuations. Hay is usually more affordable when purchased during the growing season compared to the winter months.
•If purchasing hay, buy it early. Waiting for later cuttings (which are usually higher in quality) puts livestock owners at risks of limited late-season supplies and higher prices. Having a good working relationship with a hay supplier can help ensure a consistent and reliable source of hay products and/or corn silage.
•Plan in advance. Budget for the price increases in feedstuffs and re-evaluate how many livestock you can afford to feed. Unfortunately, increases in feedstuffs are not always balanced by higher prices for livestock products.
•Finally, try and keep the hay type (grass or alfalfa) or forage product consistent in the diet or ration. Constantly changing hay types can lead to health problems, especially with horses, and can affect production outcomes in cattle.
Comments from the southeast and the north
Extension specialist Ryan Miller, Rochester, reports that crops are more variable than normal. He spent some time last week in southern Steele and Freeborn counties. He saw fields that were considerably drier south of Highway 30; reports were that crops were drier and worse as you headed into the southwestern part of the state.