Mild temperatures have kick-started an early planting season for 2012, as well as the potential for increased pests and disease pressures for growers. In fact, entomologists already are seeing significant captures of black cutworm and true armyworm in Iowa, Missouri, Indiana and Illinois.
Scouting your fields is one of the best ways to successfully manage damage to young crop plants. "Below freezing temperatures normally kill most pests and diseases or sets them back a bit," says Paula Davis, senior manager for insect and disease traits at Pioneer Hi-Bred. "Given this year's mild winter conditions, however, we are likely to see insect and disease activity earlier and more of it."
Because insecticide and fungicide seed treatments vary in the degree of control against different pests and diseases, Davis says farmers should keep a close eye on their crops as the growing season progresses.
Potential crop insect pests to watch for in your fields this spring
Several insects should be carefully monitored during the planting season and when crops emerge and are in the seedling stage.
Black cutworm – Black cutworm moths are most commonly drawn to weedy fields with high plant residue and weedy field boundaries. The cutworms lay eggs in the fields which hatch into larvae (worm stage) which can clip off corn seedlings. Clear, tilled fields generally see lower levels of infestations. Fields that use no-till or conservation tillage and use a burndown herbicide to control weeds are still at risk. A timely application of a burndown herbicide in spring can kill potential weeds that are the host plants that attract the cutworm moths for egg laying.
Davis recommends that, if you are using a burndown herbicide, you should wait at least a week before planting the corn to reduce the risk of cutworms moving from dying weeds to seedling corn. Another good protection against black cutworms are corn hybrids with Herculex I technology.
True armyworm – True armyworm moths migrate north into Iowa and the Corn Belt in the spring and prefer to lay eggs in grassy areas. Small grains such as oats and wheat, and pastures, and corn planted near grassy areas, are at greatest risk of damage.
Corn flea beetle – Corn flea beetles can cause severe plant damage and reduce yields through the possible transmission of Stewart's bacterial wilt. Although most corn hybrids are resistant to Stewart's bacterial wilt, it is still important to scout fields of young corn for flea beetles. The most effective management tactic is to use an insecticide seed treatment first—when you plant the corn. Insecticides also may be applied later to the young corn plants as foliar sprays--if populations of this insect are abundant--according to each state's recommended threshold.
Bean leaf beetle – Mild winters increase overwintering survival of bean leaf beetles. Adults are strongly attracted to early-planted soybean fields – making the newly emerging plants more at risk for damage. When scouting for bean leaf beetles, look closely in soil cracks or under crop debris where they typically like to hide.
Potential diseases to monitor in corn and soybean fields this spring
Pythium and Phytophthora – These water molds are favored by cool, wet conditions that delay emergence. Phytophthora is much more aggressive when soil temperatures are above 55 degrees and soils are saturated for more than 24 hours.
"Seedling diseases caused by fungi can be extremely destructive on corn and soybeans," says Scott Heuchelin, Pioneer research scientist in field pathology. "Fungicidal seed treatments are a great way to protect the seedling for the first few weeks until the plant has emerged and is well established," he says. "Suboptimal field conditions, such as prolonged saturated soils, can diminish a fungicidal seed treatment's effectiveness. Saturated soils also stress the germinating seed with low oxygen conditions that make germinating seeds more susceptible to fungi such as Pythium and Phytophthora."
Management suggestions: Compared to other years in the spring, the importance of scouting your fields for insect pests this spring has never been greater. Fields with previous seedling blight issues and no-till or non-rotated fields are at greater risk of seedling blights. "To catch possible problems early on, ideally growers should examine their fields at least once a week and observe emergence," he says. "Delayed or uneven emergence may indicate a fungal or insect pest is affecting seedling establishment."
Heuchelin says if there are any indicators of pest or disease pressure, growers can look to their local Pioneer agronomist for guidance. For more information about disease and pests in your area, visit the Pest and Disease Guide on www.pioneer.com under the Agronomy tab or contact your local Pioneer seed sales professional.