With June’s arrival nut sizing begins in earnest. This means the nuts will grow rapidly and as they grow they will expose newly developed and unprotected tissue. Your scab spray schedule is designed to protect that growth for 2 weeks (the amount of time for new tissue to develop and be exposed). The frequency of rainfall has increased over the last couple of weeks, creating ideal conditions for scab development. There has been a little leaf scab here and there in the state but for the most part it remains under control at this time. However, from here on out it is critical to protect the nuts until shell hardening is completed in mid-August. This means you must spray every 2 weeks (even in dry weather on Desirable and Pawnee because the dew or humidity is enough to generate scab on susceptible varieties) during this time. Tighten up to 10 days when you get 2 or more rain events of 0.1″ or more since your last spray.
While there are a number of fungicides to choose from, Elast at 50 oz/A or a combination of Elast (25 oz/A) + Tin (6 oz/A) have proven to be highly effective materials to use during this critical period. As long as you have not used it much pre-pollination, use Elast or the Elast combo for a couple of sprays and then rotate back to one of the DMI/Strobi mixes (Absolute, Quadris Top, Quilt, Custodia) for a spray then go back to Elast or Elast/Tin again. If pressure is extreme (i.e. lots of rain), Quadris Top would likely be the best option to rotate in when the DMI/Strobi is needed on susceptible varieties like Desirable or Pawnee.
