Autumn Defoliation: Effects on Nitrogen, Vegetative Growth, and Fire Blight Chuck Ingels, UCCE Sacramento County Jenny Broome, UCCE Sacramento County Kitren Glozer, UCD Plant Science Dept. Grower Cooperator: Topper Van Loben Sels

Research on Effects of Chelated Cooper + Urea Used in peaches: fertilize, reduce leaching N rapidly absorbed, rapidly translocated Defol. used in nurseries – earlier harvest Chelated Cu more effective than ZnS04 Cu induces leaf abscission  ↓ N remobilization  ↓ N reserves in tree Urea acts as surfactant, enhancing copper Adding urea leads to increased reserve N

Defoliation Trial Defoliant: 1% CuEDTA (Chelated copper, 3.3 gal.) + 2% L-B urea (16.7 lbs.), 100 gpa Treatments (Dorm. oil sprayed 1/3/08 @ 37 CP) Oct. 11 (1 CP) 3. Nov. 20 (7 CP) Oct. 20 (3 CP) 4. Untreated Randomized complete block design 3 replications of one row each Treated rows are 3 rows apart

Photo Oct. 20, 2007 (Spray applied Oct. 11) 4

Photo Nov. 20, 2007 (Spray applied Oct. 11) 5

Measurements Leaves sampled for N content 4/23 & 6/11 Blight strikes counted (none) Inoculated vigorous shoots with blight 5/28 Weighed prunings to evaluate growth Surveyed growers about N fertilization 11 growers, 4,300 acres of Bartletts

Effects on Leaf N Levels Spur and Shoot Leaves Combined

Pruning Weights (4 Trees/Plot)

Fire Blight Lesion Length

Fertilizers Used by Growers