650 EXPERIMENT STATION EECOED. 



At harvest time it was found that 90 per cent of the apples were free from 

 scab, and very few showed any signs of black rot, while other nearby unsprayed 

 orchards were badly attacked by the scab. 



A preliminary report on the effects of arsenical compounds upon apple 

 trees, D. B. Swingle and H. E. Morris {PhytopatJiolofjij, 1 {1911), No. 3, pp. 

 79-93, pis. 2). — The results are given of experiments made in an orchard which 

 had never been sprayed with any arsenical, in which the effects on the bark of 

 fruit trees of the common insecticides were tested. Tests were also made as to 

 which compounds are the most injurious, and the nature and extent of the 

 injuries. 



The following compounds were applied: Arsenic acid (pure), arsenic trioxid 

 (highest purity), arsenic disulphid, arsenic trisulphid (technical), calcium 

 arsenite, lead arsenate (technical), Paris green, sodium arsenite (pure), and 

 zinc arsenite. The chemicals were applied to branches from i to 2i in. in 

 diameter, on bands of absorbent cotton which were wrapped about the limbs in 

 such a manner that the chemicals made a uniform layer of about 4 in. wide, 

 and were kept wet with distilled water. Crowns from 3 to 5 in. in diameter 

 were also treated, by digging a shallow trench close around the tree, partly 

 filling it with the chemical suspended in water, and replacing the earth. Tabu- 

 lated data are given showing the kind of arsenical used, the amount of the 

 arsenical by weight, the variety of tree treated, the diameter of the treated 

 portion, wounds under the bandage holding the chemicals, and the extent and 

 character of injury. Investigations were also made as to the number of cells 

 in the corky layer of smooth bark and in the furrows of rough bark. 



It was found that serious injury to apple trees may result under certain con- 

 ditions from the application of so-called insoluble arsenicals, and that recent 

 wounds through the outer bark, functional lenticels, and dormant buds permit 

 the absorption of arsenicals in solution, recent wounds being especially dan- 

 gerous. The cutting off of water sprouts from the bases of trees in early spring 

 and the subsequent accumulation of arsenicals used as insecticides about the 

 unprotected wounds were found to be dangerous. White-lead paint applied 

 to these wounds will protect against arsenical injury, even when the paint is 

 put on just before the spraying. 



The most noticeable symptoms of rapid arsenical injury through the bark are 

 a discoloration of bark and outer wood along definite lines up and down the 

 stem and a dull spotting of the leaves, followed by wilting, shriveling, and dry- 

 ing. The injury seems to be due more to the soluble impurities in the arsenicals 

 than to the slight solubility of the compounds themselves. Arsenic trisulphid 

 when applied to the bodies of trees did not seem to be more safe than the other 

 arsenicals in common use, but zinc arsenite gave practically no injuries under 

 the most severe tests. 



Researches on the diseases of the grape, J. Capus (Bui. Mens. Off. Rcnseig. 

 Agr. [Paris], 10 {1911), No. J,, pp. 456-Jf6.'f). — Two lines of study are reported, 

 one on the spread of the black rot and mildew in 1909, and the other on the 

 comparative efficacy of different copper sprays as determined by the length of 

 action of each on the vines. 



It is stated that 2 sets of conditions govern the ease with which these diseases 

 attack the grape, as follows. The first set includes diminished daily growth of 

 the branches, the disappearance of starch from the upper internodes, and the 

 cessation of growth of the rootlets, accompanied by heavy rains which wet the 

 earth and by a lowering of the temperature. The second set includes the 

 atmospheric conditions such as sufficient warmth and moisture for the germina- 

 tion of the spores. When these 2 sets of conditions coincide the infection will 

 be certain and rapid, and the intensity of each attack under these favorable 



