■5- 



The toxic component of walnuts is a chemical compound known as 

 juglone. It is toxic to fungi and bacteria and has even been used in cur- 

 ing skin diseases, including ringworm. In field tests in 1943 at the 

 Connecticut Station on the control of black spot of roses, juglone gave 

 a degree of control equal to that of 2^ times as much 325 mesh sulfur, 

 the standard control for this disease, 



Juglone occurs definitely in the black v/alnut and the butternut, 

 and probably in the English walnut. It is formed by the oxidation of hydro- 

 juglone which is a non-toxic substance occurring in the inner bark and 

 green husks of the nuts. V/hen roots of other plants contact these parts, 

 oxidation produces the toxin and the roots are injured or killed. Thus 

 root contact is required. In some cases, ihe plant root systems are shallow 

 and do not contact the deeper roots of the walnut, especially in plowed 

 ground. Also, some plants may send out sufficient surface roots to keep 

 them alive in spite of injury to the deeper roots. This explains why many 

 plants are not adversely affected wh'-in grown near walnut trees. However, 

 the fact does remain that many plants, including fruit trees, often will 

 die or not do v/ell in the vicinity of walnut trees. This is not a myth - 

 it is a fact, 



— Lawrence Southv/ick 



RELATION OF McINTOSH DROP TO MGNESIIM DEFICIENCY 



We are just beginning to realize how low in magnesium are many of 

 our crchard soils. This problem is not confined to the lighter soil types 

 but may be equally severe in badly eroded soils and in other soils which 

 are shallow because of hardpan, waterlogging or ledge. Strongly acid soil 

 conditions, brought .about by the continued use of sulfur, has further ag- 

 gravated the situation. Much of the apple leaf scorch previously attributed 

 to spray injury is now known to be due to a shortage of magnesium. Fairly 

 liberal use of potash fertilizers in some orchards has tended to accentuate 

 the magnesium deficiency by creating a lack of balance between potassium 

 and magnesium. Not that potassium isn't a highly essential mineral element. 

 But a tree might "worry along" on a low magnesium diet provided other ele- 

 ments were also low. As v;e step up the level of one element, we seem to 

 create a demand for more of the others. Acontent of magnesium in the leaves 

 amounting to at least ,2% of the dry matter appears to be necessary. 



Observations in Massachusetts orchards shov/ a much greater tendency 

 of Mcintosh apples to drop from trees which are deficient in magnesium. 

 Both leaves and apples tend to drop prematurely if the magnesium supply 

 is very limited. It is .also well known that hormone sprays and dusts 

 fail to produce the desired results under these conditions. One Middlesex 

 County grower who has recently corrected a magnesium deficiency, reports 

 that last fall, for the first time, he got a definite response to- the pre- 

 harvest spray. Our first job as Mcintosh apple growers is to restore the 

 magnesium balance. If that is done, the Mcintosh drop problem may partially 

 disappear. 



