■9- 



Zn-containing fungicides contribute a certain amount of zinc 

 to the tree, but are not adequate to correct deficiencies. Zn 

 chelates (EDTA) offer the most satisfactory control. These are 

 compatible with many of the commonly used pesticides. Rates as 

 suggested by the manufacturer would be adequate under most circum- 

 stances. In relation to leaf analysis results, the following may 



be suggested: 



Leaf 



Zn (ppm dry wt . ) Zinc treatment 



55 to 50 Continue present program. If zinc fungicides 



were used add 1 spray of ZnEDTA (1 lb. per 

 100 gallons dilute rate) at first cover. 



20 to 35 One spray of ZnEDTA (1 lb. per 100 gallons 



dilute rate) at first cover. 



below 20 Two sprays of ZnEDTA (1 lb. per 100 gallons 



dilute rate) at tight cluster plus first cover. 



Correction of Zn deficiency is often difficult. Contributing 

 factors include cold soil temperatures during the spring, high soil 

 organic matter content, and high levels of P in the soil. The ratio 

 of P/Zn sometimes indicates the Zn status more accurately than Zn 

 alone. Ratios over 150:1 generally are associated with Zn deficiency, 

 while ratios below 100:1 indicate adequate Zn availability. Var- 

 ieties such as Delicious and Golden Delicious usually accumulate 

 higher levels of P and are more sensitive to Zn deficiency than 

 varieties like Mcintosh. Severe pruning results in temporary relief 

 from Zn deficiency. One difficulty in diagnosing Zn deficiency from 

 leaf analysis results from the lack of normal dilution because 

 growth is limited. 



Similar treatments are suggested for other tree fruit crops. 



Mangane se (Mn ) shortages are most likely to occur under high 

 pH conditioiTs~(generally above 6.3). Coarse soils, especially those 

 of glacial-till origin, may be inherently low in manganese. Trees 

 on these soils may show Mn deficiency at lower pH levels. 



Mn-containing fungicides applied in 2 or 3 cover sprays, or 

 a single spray of Mn sulfate (2 to 4 lbs. per 100 gallons dilute 

 rate) applied 1 to 2 weeks after bloom are usually adequate to over- 

 come Mn deficiencies in tree fruits. In a preventive program., 

 these applications might be suggested where leaf samples are found 

 to contain less than 35 ppm Mn, or where symptoms are evident. 



