April, '10] BALL AND OTHERS: ARSENICAL POISONING ]93 



died. Mr. L. W. Sweitzer's orchard, near Delta, presents a typical 

 case of this kind. The Jonathans are becoming affected in small 

 groups, while the blocks of Winesap, Gano and Black Twig are ap- 

 parently uninjured. Upon examining the soil in the places where the 

 Jonathans were dying, it was found that in every case the marl was 

 near the surface in these areas, so near that oftentimes it would be 

 pulled up with the roots of the trees. As has been noted by previous 

 writers 3 when large limbs are sawed off from affected trees, they con- 

 time to bleed and deposit large masses of calcareous material. It is 

 possible that the excess of this material in the sap is the cause of the 

 trouble, but whatever it is, the Jonathan seems to be practically the 

 only tree that is affected in this region, the Ganos in this same orchard 

 being very healthy. Located as these orchards are on rather high 

 and well drained mesa land, there is little trouble from alkali or 

 seepage. The Ashenfelter orchard near Montrose is located upon a 

 mesa in which this marly layer is particularly close to the surface and 

 here the condition of the trees suggests a lack of fertility in the soil. 

 This condition was apparent in this particular orchard before it 

 came into bearing, and, therefore, before sprays were applied. This 

 condition has been referred to as systemic arsenical poisoning. 



Summary of Orchard Investigations: It will be seen from the 

 above descriptions that in the regions like the Pajaro Valley, the 

 Rogue River and Hood River Valleys, where little or no irrigation 

 water is used, and where if anything the orchards suffer from lack 

 of water, and the soils are comparatively free from alkali, the trouble? 

 under consideration are entirely unknown. 



That in every district in which the alkali is present in sufficient 

 amounts to appear on the surface and where water is sufficiently 

 abundant to cause seepage in the lower districts, that more or less 

 of these root rot or collar rot conditions occur. In bad cases of seep- 

 age whole orchards are stricken within a year or two, oftentimes after 

 they have borne a number of heavy crops. This may be due to a 

 gradual rise of the ground water, or to the gradual extension down- 

 ward of the roots of the trees. In milder cases, only here and there a 

 tree is affected and these often linger along for a number of years, 

 sometimes in a dry year, partially recovering, only to be stricken 

 again in a wet one. If there is any perceptible slope to the ground 

 the trouble will usually be more marked on the lower end of the 

 irrigation furrows. Where alkali is evidently the cause of the death 

 of the trees, no variety seems to be exempt, all being equally affected. 



3 Headden, Col. Exp. Sta. Bull. 131, p. 25, '08. 



