Stripe Rust Update

 

Growers should be aware that Stripe Rust was confirmed in different parts of Virginia, including the Eastern Shore, over the weekend.  As mentioned last week, it was confirmed in Kentucky, North Carolina, and Tennessee the previous week.  Currently the level of infection is low in areas of VA where the pathogen is found, so the potential for any significant movement into our area is low.  Regardless, growers in southern parts of Sussex county Delaware and Southern counties in Maryland should plan on scouting for the disease over the next 2 weeks, as the forecast continues to look favorable for potential disease development.

 

The fungus produces yellow to orange pustules that will rub off on your hands, leaving a rusty residue.  Often the pathogen will form pustules in strips following the leaf veins (Figure 1).  Under cool wet conditions the pathogen can spread rapidly on susceptible varieties.  If stripe rust is detected, applications of a premix fungicide at early flag leaf will provide excellent control, provided that significant infections have not already occurred.  Fungicides containing a strobilurin – (QoI, Group 11) fungicides should not be applied later than Feekes 8/9.  Make sure you scout your fields and assess it for diseases before pulling the trigger.  Look for foliar disease symptoms on upper, green foliage.  In addition to stripe rust, look for leaf blotch complex (tan spot, Stagonospora) and powdery mildew.  Temperatures have been colder than optimal for these diseases of late, but it is always best to check to see if diseases are present and where they are located in the canopy.  In dense canopies the microclimate can differ from the ambient conditions, sometimes promoting disease.