-9- 



Boron Toxicity (B) . Toxicity symptoms of this element are observed in a few orchards 

 each year. Symptoms occur on bearing trees sprayed with a foliar application of B, 

 on trees fertilized with B the year of planting, or bearing trees that received excessive 

 rates of B containing fertilizer. Figure 6 shows typical foliar symptoms of B toxicity. 

 The symptoms are characterized by loss of chlorophyll (green coloration) from along 

 the midrib and larger lateral veins. The symptoms are first apparent at the base of 

 the leaf blade. In severe cases, loss of chlorophyU is more extensive than shown in 

 the picture. 



Boron Deficiency (B) . Occasionally B deficiency is so acute in pear trees that the 

 fruits become malformed and cracked (Figure 7). B deficiency on apple trees is less 

 common than B toxicity. It is very easy to prevent, thus it is embarassing to have 

 the disorder. It certainly hurts financially because all the fruit where deficiency exist 

 should be sold only for cider. 



The most common symptom of B deficiency is found internal in fruit being characterized 

 by brown, round or irregular shaped lesions of about 5 inch diameter (Figure 8). The 

 dead cell masses become dry, hard and corky before harvest. Fruit affected with the 

 disorder will have a pebbled surface (particularly noticeable on Cortland), open calyx, 

 and abnormally dark color as they mature. However, frequently the first recognition 

 of the problem is excessive preharvest drop. 



Figure 6. Boron toxicity symptoms on apple leaves. 



