Wheat
will begin flowering in the southern portion of Wisconsin over the next several
days. This is a critical time to determine if the crop is at risk for Fusarium
head blight (FHB). Following from our previous updates, a check of the risk map for
today indicates a low risk of infection across the state. Weather over the next
week is forecasted to range from overnight temperatures around 50F to daytime
highs around 75-80F (Air Resources Laboratory, ready.arl.noaa.gov). A similar check for
rainfall suggests an extended dry period, with isolated showers or
thundershowers in the forecast. An examination of several weather stations in
the main wheat production areas indicates low amounts of accumulated rainfall.
Based on this, the risk for FHB this week appears to be low. Fungicide
decisions should be based on a combination of this risk as well as active
scouting of fields to determine if any foliar diseases pose a risk to the upper
canopy.
A
reminder, as the wheat crop moves into flowering, it is critical to understand
the difference in harvest restrictions related to the different fungicide
products. Primary compounds recommended for control of FHB have harvest
restrictions of 30 days (Proline, Prosaro, and Caramba). These products also
carry good to excellent ratings for control of several major foliar diseases
(powdery mildew to the different rust diseases). However, as we earlier pointed
out, it is important that you take the time to scout fields to determine if the
level of disease warrants a fungicide application.
The most effective timing for FHB management is Feekes 10.5.1 Recent work has shown (Christine
Cowger, USDA and NCSU) that post-flowering infection can occur. However, I
would say that going in early doesn't get you the best efficacy. There are
still questions related to the early, pre-anthesis risk of infection however, because
the greatest risk of infection is at that early flowering period, this is the
optimal timing.
Joint contribution from Shawn Conley; State Soybean and Small Grain Specialist; University of Wisconsin, Madison and Dr Paul David Esker, University of Costa Rica.
