ISSUE 4 June 3, 2010
WINTER WHEAT AND HEAD SCAB RISK
Winter wheat fields in southeast and south central counties of ND are in the head emergence to early flowering stage in many fields (June 1). The Fusarium head blight (fhb = scab) model indicates very low risk of scab infection in these locations at this time. Recent weather in the south and eastern portions of ND was not favorable for infection as relative humidities were very low.
In contrast, relative humidities were very high over the past week in the northwest and north central regions, and the model does indicate high risk of infection for any winter wheat flowering in the these areas of ND. However, reports from area extension specialists at Williston and Minot indicate that most, if not all, winter wheat fields in those areas are not yet headed. Growers with winter wheat in the boot stage to early heading stages should keep watching the scab forecast and weather conditions for potential risk of scab.
NO RUST OBSERVED YET IN ND
No stripe rust or leaf rust of wheat was observed in Ransom or Sargent county scouting of winter wheat and spring wheat on June 1. We will keep looking in our scouting program, as stripe rust is being observed commonly on winter wheat in Nebraska now, as well as low levels of leaf rust.
TAN SPOT IN WHEAT
Tan spot fungal leaf infections are the most common disease observed in winter and spring wheats. Levels of infection vary considerably, depending on amount of old wheat residue present and recent weather conditions. Where residue is abundant and dews have occurred, tan spot is severe. The NDSU Small Grain Disease forecasting model indicates risk of tan spot in those areas of the state where more rainfall has occurred in the past week.
Extension Plant Pathologist
CONTROLLING WILD AND VOLUNTEER SUNFLOWERS IMPORTANT FOR RUST MANAGEMENT
It is possible for sunflower rust to complete its life cycle on wild and volunteer sunflowers; this can exacerbate rust in two ways. First, when the pathogen completes its life cycle race changes are more likely to occur. This can lead to new races that overcome resistance in commercial hybrids. Secondly, when the pathogen completes its life cycle, the disease shows up earlier in nearby commercial fields. The earlier that rust appears in commercial fields, the greater the yield loss potential. If possible, destroy wild or volunteer sunflowers that are next to commercial plantings. Although it won’t prevent rust, it may delay the disease and help limit potential race changes.
Wild sunflowers can lead to increased problems with sunflower rust.
Extension Plant Pathologist
IPM SCOUT CORRECTION
Last week we introduced the readers to the IPM scouts for 2010, and introduced you to one scout incorrectly. The IPM – scout in the Central and South Central region is Rick Glatt, and he will be advised by Greg Endres (Area Extension Specialist – Carrington)
Sam Markell and Marcia McMullen
Extension Plant Pathologists