Northern corn leaf blight (NCLB) has been reported in numerous fields in Iowa. Most of the reports have come from central and western Iowa, but since the pathogen that causes this disease is spread by wind and rain, the disease could be more widespread.
Soybean samples have been arriving almost daily at the ISU Plant and Insect Diagnostic Clinic this year. Early season problems were primarily damping off diseases and problems with herbicide carryover or sometimes a combination of the two.
We continue to receive several questions about Northern corn leaf blight, Goss’s wilt and fungicides. Here is some additional information.
Basics of fungicides
Parts of rural Iowa are abuzz about fungicide use to manage some emerging diseases, and we have received several questions about the basics of fungicides. A quick reminder, APS PRESS recently published a book geared towards farmers and agronomists on the basics of fungicides.
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.
The lack of reliable traits to distinguish Palmer amaranth and waterhemp during vegetative stages complicates efforts at stopping the spread of Palmer amaranth across the state. However, both plants should be in full reproductive mode at this time, greatly simplifying the identification of the two amaranths.
While most agronomists and weed scientists prefer to identify weeds using vegetative traits, the small bracts (modified leaves) associated with flowers of Palmer amaranth and waterhemp are the most, if not only, reliable way to differentiate the two species. Palmer amaranth has relatively large, green bracts that extend well beyond the other flower parts, whereas on waterhemp the bracts are similar in length to the tepals surrounding the seed capsule. On close examination, Palmer amaranth’s bracts on mature female plants are easily seen protruding from the plant’s seedheads without the use of a hand lens. Redroot and smooth pigweed also have large bracts; however, these species have hairy stems in contrast to the smooth stems of Palmer amaranth and waterhemp.
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.
AMES, Iowa – Field Scouting Basics Workshop, an Iowa State University Extension and Outreach educational program, will be Monday, May 18, at the Field Extension Education Laboratory near Boone, Iowa. Designed for beginning-level crop scouts, the half-day course provides hands-on, in-field experience to crop scouts for the 2015 growing season.
The Iowa State University Integrated Pest Management (IPM) Program is pleased to present the 7th annual Crop Scouting Competition for Iowa youth.
Iowa State University Extension and Outreach has published the Field Crop Scouting book as an online learning tool for students and ag professionals in Iowa. This interactive textbook allows individuals to acquire knowledge about crop scouting topics such as corn and soybean growth stages, insect identification, crop diseases and weed identification through a self-paced, innovative design.