I'm concerned about my fifteen-year-old Apricot tree. In the spring the growth is lush and vigorous, but in the early summer one branch or limb will appear to become sick and dies. Eventually, I have little or no tree left. My other Apricot tree died in a similar fashion. What can be done to prevent this?
Answer:
Phytophthora Root Rot and Euypta Die Back are the two primary causes for sections of the canopy in Apricot trees to die. They effect major and minor branches/limbs. Phytophthora Root Rot is a soil borne fungus that attacks the roots of Apricot, along with Cherry, Peach, Nectarine and Plum trees. Root rot is the primary suspect when a limb or section of a tree fails to break dormancy and leaf out in the spring. It's also the reason when for no apparent reason the foliage on a branch collapses/wilts and turns brown shortly after the rainy season concludes. You would expect this problem in clay soils that drain poorly and receive excessive summer irrigation. A good soaking with a large watering basin once every three weeks is sufficient for mature Apricot, Cherry, Peach, Nectarine and Plum trees. Phytophthora Root Rot is a slow developing disease. You'll find more information at http://www.ipm.ucdavis.edu/PMG/r5100611.html.
That being said, I don't think this is your problem. Instead, Euytpa Die Back would be my educated guess. Euytpa Die Back is only a problem with Apricot trees and grapes. It's an airborne fungus that enters the tree through the pruning wounds made during the winter months during wet and moist conditions. You need a week or so of dry weather so the pruning wounds callus over. The wet conditions last year may when you pruned a bigger concern than in 2015 when it was a non issue. The effected branches or limbs collapse around Memorial Day or in the early summer for no apparent reason. This is easily corrected by changing the time of the year you prune. It is now recommended to prune Apricots from August through early November. Although the foliage hasn’t turned yellow and dropped, they’re in the early stages of dormancy as multiple their growing and fruiting cycle is finished for the year. You'll find more information at
http://www.ipm.ucdavis.edu/PMG/r5100911.html.
Note:
When fruit trees are under stress from Phytophthora Root Rot and or Euypta Die Back, borers can attack and be a secondary problem. It’s not uncommon for globs of amber colored sap to be on the limbs and branches. It's very possible for an Apricot to be suffering from both problems concurrently. The ideal prevention is to keep the tree healthy by not over watering during the summer months and avoid planting under the canopy. Watering once every three weeks is sufficient. Each tree should have a watering basin around them that is six to eight inches high and extends from the trunk to a foot beyond the drip line. This basin is filled multiple time when you water.
