Grasshopper activity has been noted this week in Iowa. These insects feed on grasses and weeds, and can become field crops pests. In corn and soybean, feeding is frequently, but not always, restricted to field edges. When crop injury does occur, it usually is related to drought conditions due to a reduction in natural vegetation.
Since 2000, soybean aphid has been the primary soybean insect pest in Iowa. Infestations are sporadic and unpredictable, but this insect has the ability to cause significant yield loss during periods of optimal reproduction. Several notable infestations have been reported, particularly in north-central Iowa, this week, and therefore scouting to determine population densities is strongly encouraged. Fields that have a fairly uniform infestation with low densities (e.g., 50% of plants infested with an average of 40 aphids per plant) should be closely monitored in August.
Soybean diseases are starting to show up in Iowa fields this growing season. In an On-Farm Network trial in north central Iowa, brown stem rot (BSR) was recently found. This disease is caused by the fungus Phialophora gregata, and infection can result in yield loss for Iowa farmers.