put the rain gauge back up in my backyard today.  Showers – OK, 30-90% chance of showers -- are predicted for the next three days.  Spring rains can help bring about prune rust infections on prune leaves.  Infested leaves will drop and defoliated trees produce small fruit. 

If you haven’t already started looking for rust symptoms in your prunes, you should look after this series of cold storms roll through.  Thursday is supposed to be clear and 79.

Details on rust scouting in prunes can be found at:  http://ipm.ucdavis.edu/PMG/r606100611.html.

Basically, every week beginning May 1, look at 40 prune trees per block.  Look for any rust spots.  Spray (sulfur or labeled, Group 3 or 11 fungicide) once you see the first spot (see photos).  Keep checking after you spray.  If the number of trees with rust spots goes up, spray again.  See the new UC ANR Fungicide Efficiacy and Timing publication at:  http://ipm.ucdavis.edu/PDF/PMG/fungicideefficacytiming.pdf

Don’t let rust sneak up on you.  It is easy to scout for and control as long as you know what you are looking for.   Keep a healthy and profitable orchard with a strong canopy that can produce high quality prunes -- monitor prune rust and control when needed.

Prune leaf with three rust spots viewed from top and bottom.  Rust spots appear angular and yellow from the top and rusty brown when viewed from the bottom.