-8- 



with magnesium compounds has become quite prevalent. Recently it was found 

 that tung trees responded markedly to magnesium applications. 



Symptoms of magnesium deficiency on apple trees have been recognized 

 only very recently in this country although the trouble has been knowii in 

 England, Canada, and New Zealand for several years. It is true that the 

 symptoms have been observed for a number of years but the cause was usually 

 identified as drought injury, spray burn, etc. Typical magnesium deficiency 

 symptoms usually appear in late summer. In late July or August apparently 

 normal trees develop a leaf scorch which characteristically appears as irre- 

 gular areas on the leaf blades. This necrosis is often preceded by a fading 

 out of the green color and with some varieties there is considerable leaf 

 mottling and coloration. The first leaves to show deficiency scorch are 

 usually the older ones near the bases of the current year's shoot growths 

 and the scorch may progress upward as the season advances. Affected leaves 

 often drop early, leaving bare stretches of wood. In serious cases most of 

 the foliage may be affected and pre-harvest drop of fruit is hastened. Fur- 

 thermore, apple quality is inferior and t ree growth is reduced. Seriously 

 deficient trees are not productive nor profitable. The extent and severity 

 of magnesium deficiency in eastern apple orchards seems to be increasing. 

 Hence, effective control measures are eagerly sought by groovers. 



Several approaches to the problem have proven more or less successful. 

 Adequate soil applications of magnesium oxide and magnesiijra salts (such as 

 Epsom salts) have given generally good results on young trees, but a much 

 more delayed response has been characteristic of older trees. In meiny tests 

 high magnesium or dolomitic limestone applications have been relatively in- 

 effective unless the lime was thoroughly dug into the soil around the roots 

 as was done by Boynton in New York. 



The inclusion of Epsom salts in two or three post-blossom spray appli- 

 cations has been effective as vias also the use of high magnesium spray lime 

 in the cover sprays. Investigators have also shown that magnesium deficiency 

 may be worse under condxtions of high potassium nutrition, Boynton recently 

 reported that magnesium deficiency leaf blotch v/as induced in Mcintosh apple 

 trees following fertilization for three or more years with potash. 



Give fools their gold 



And Itnaves their power. 

 Let Fortune's bauble 



Rise or fall. 

 Who sov;s a field 



Or trains a tree 

 Or plants a flower 



Is more than all. 



— -Whittier 



