Early Maturing Wheat in the Lebanon area is beginning to flower and conditions are favorable for infection. I talked to a local grower. From his spray records last year he sprayed May 25th when flowers were out this year might be somewhat different. Prosaro and Caramba, only provide about 50-60% suppression when applied at flowering. Depending on the weather conditions, and the baseline level of disease and toxin, 50-60% suppression may be sufficient to avoid or reduce price discounts and dockage. For instance, 50-60% suppression would bring vomitoxin levels from 4-6 ppm to 2-3 ppm, or under more favorable weather conditions, from 8-10 ppm to 3-5 ppm. So, this is what you can expect, suppression, not 100% control. Efficacy is greatly reduced when applications are made before or after flowering, so expect little or no vomitoxin suppression from application made for foliar disease control between flag leaf emergence and heading.
Flowering is when anthers (the yellowish male part of the flower) are seen sticking out of the heads(see picture below). This typically occurs 3 to 5 days after heading. Anthers first emerge in the central portion of the head – this is called early anthesis or early flowering and is the growth stage at which fungicides should be applied for best results against scab and vomitoxin. If conditions are warm, it takes less time between heading and flowering, however, under cooler conditions, it may take longer, up to 5 or more days after heading, and flowering may last for several days. Main tillers (main stems) usually flower first, followed by secondary tillers (side stems). So, the flowering pattern may vary from field to field, depending on the variety and local weather conditions. This variation affects the risk for scab and vomitoxin and fungicide efficacy against the disease and toxin. In general, a well-timed application to a field with a narrow flower window will likely provide better scab and vomitoxin suppression than a poorly timed application or an application made to a field that flowers over several days.
Prosaro and Caramba are the two choices for application at this time.Prosaro 421 SC 6.5–8.5 ounce/acre 30 days HI
prothioconazole + tebuconazole
Caramba 10.0–17.0 ounce/acre 30 days HI