Mildew starts in spring some people say scab. Only control either one is with big fan sprayer. Air circulating around tree help if in earily morning. Tree health will help fertilizing with 10-10-10 4 pound per inch of diameter if got large tree as posted lets take 30 inch diameter tree times 4 = 120 lbs to that tree. Any tree having promblems as your need zinc sulfat. You can get zinc about any farm store in south Georgia. It will take 5 years bring trees out stavation one year want do anything to tree third year you will see turn around and start production 5th year max out. One thing should warn if these trees staved for long time all limbs be long and weak the fertlizing set heavier folage wind brake off. So good cutting limbs back to short length help tree come into production prunning always help pecan tree be stronger.