Keep alfalfa weevils in mind while scouting for stands and evaluating for winter injury. A recent ICM News article gave some great tips for assessing winter injury and providing additional resources. Adult alfalfa weevils become active and start laying eggs as soon as temperatures exceed 48°F. Alfalfa weevil eggs develop based on temperature, or accumulating degree days, and hatching can start around 200-300 degree days.
Integrated Crop Management News
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Seedcorn maggot is a seed and seedling pest of corn and soybean. Plant injury is especially prevalent during cool and wet springs. The larvae, or maggots, feed on germinating corn and soybean seeds or seedlings (Photo 1). They can feed on the embryo, delay development or kill the plant. Infestations tend to be field-wide instead of having a patchy distribution like for many other pests. To confirm seedcorn maggot injury, check field areas with stand loss and look for maggots, pupae and damaged seeds (e.g., hollowed out seeds or poorly developing seedlings).
This spring's weather conditions may be slowing down corn planting but soybean planting has not yet been impacted. As of May 5, soybean planting progress is estimated at 8% compared to 11% for the 5-year average (USDA-NASS, 2019). However, because of recent rains and corn planting delays there is concern that soybean planting will soon fall behind. In this article, we discuss the soybean yield potential and maturity selection considerations as planting progresses into late May and possibly June.
Black cutworm (BCW) is a migratory pest that cuts and feeds on early vegetative-stage corn. Black cutworm moths arrive in Iowa and other northern states with spring storms each year. These moths lay eggs in and around crop fields, and emerging BCW larvae can cut seedling corn. This pest is sporadic, making it essential to scout fields to determine if management is needed.
Every spring, alfalfa growth and development is different due to variations in climatic, variety, stand age and other crop production factors. With the 2019 growing season being off to a cooler than normal start, this has slowed alfalfa growth this spring. This is a good reminder that while calendar date may be one method used to determine when to harvest first crop alfalfa, this method is not the best method to use. Instead, the PEAQ method (Predictive Equations for Alfalfa Quality) developed by the University of Wisconsin does a better job.
Bean leaf beetle adults (Photo 1) are susceptible to cold weather and most will die when air temperatures fall below 14°F (-10°C). However, they have adapted to winter by protecting themselves under plant debris and loose soil. Each spring, adult beetles emerge from overwintering habitat and migrate to available hosts, such as alfalfa, tick trefoil, and various clovers. As the season progresses, bean leaf beetles move to preferred hosts, like soybean. While initial adult activity can begin before soybean emergence, peak abundance often coincides with early-vegetative soybean.
Corn planting began a couple of weeks ago and according to the May 5 USDA-NASS Crop Progress and Condition report only 36 percent of the corn crop is planted; 15 percent behind the 5-year average. The greatest progress has been in central and west central Iowa at 56 percent and 57 percent, respectively. Since May 5 there has been limited opportunity for planting to occur. Current weather forecasts for May 8 to 14 indicate two inches of rain and 20 to 30 lower than normal GDD accumulation across Iowa, which may cause additional planting delays.
As of May 6 2019, 36 percent of Iowa’s corn is planted according to the USDA-NASS. Under cool conditions (50 to 55oF soils), it may take more than three weeks for corn to emerge whereas corn in 70oF soils can emerge in less than a week (Licht et al., 2001).
As flood waters recede, the renovation of flooded pastures is just beginning. Now is a good time to check pasture plants for survival. Forage production is a function of the plant species, and their density and growth. Evaluate live plants (plant vigor), plant density, and desirable species versus weeds.
Iowa’s most significant soybean insect pest, soybean aphid, has host-alternating biology. This species has multiple, overlapping generations on soybean in the summer and moves to buckthorn in the winter. Fall migration to buckthorn is based on senescing soybean, and decreasing temperatures and photoperiod. For the majority of the year, soybean aphids are cold-hardy eggs near buckthorn buds (Photo 1). As spring temperatures warm up, soybean aphid eggs hatch and produce a few generations on buckthorn before moving to soybean (Photo 2). Tilmon et al.