ZINC DEFICIENCY OF FRUIT TREES IN EUROPE 



hy D. Mulder, Ph.D., 



Wilhelminadorp, Zeeland, Netherlands 



In 1940 Husz described, for the first time in Europe, the 

 rosette disease of apples growing in Hungary. He was able to 

 cure the deficiency by an application of zinc sulphate. 



In 1943 I was confronted with an unknown disease of "Golden 

 Delicious" apples in Holland. Because leaf injection with iron 

 sulphate improved the colour we first thought that we had to do 

 with a special form of iron shortage in that variety. Grafting ex- 

 periments showed that the symptoms were not the result of a virus 

 disease. 



In 1944 it was shown that trees which had been transplanted 

 to another soil became again healthy. In 1945 the same disease 

 was found on other varieties and the resemblance with the symp- 

 toms described, as a result of zinc deficiency, in the United States 

 was noted. 



In 1947 spraying experiments with zinc sulphate showed that 

 the symptoms are indeed due to a deficiency of zinc, at least that 

 they can be cured by application of zinc to the trees. Both the 

 spraying of 5% zinc sulphate, in winter, and of 1.5% zinc sulphate 

 with 0.75% lime, in summer, had good results. 



The information, from other regions of Europe, about the 

 occurrence of this deficiency disease is still very scarce. 



Mr. Conrad (Maag, Zurich) told me that Dr. S. Blumer has 

 noticed zinc deficiency symptoms in apples in Switzerland. 



During a visit to Denmark I found symptoms of zinc defi- 

 ciency in apples. They are attributed to the high phosphorus 

 content of the soil by the Phytopathological Service in Denmark 

 (zinc phosphate is highly insoluble). 



The symptoms of the disease in "Golden Delicious" apples are: 



