276 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



stems as an adulterant to insect powder; and in a paper published 

 under the title of The Microscopical Identification of Mowrah Meal 

 (Bassia) in Insecticides are described the methods for the detection 

 of this adulterant. Studies upon proper standards for hellebore and 

 upon methods for detecting its adulteration are approaching com- 

 pletion. 



In Department Bulletin 893, Experiments on the Toxic Action of 

 Certain Gases on Insects, Seeds, and Fungi, which was published in 

 cooperation with the Bureau of Entomology, are described the experi- 

 ments upon the action of phosgene, arsine, cyanogen chlorid, chloro- 

 picrin, illuminating gas, and carbon monoxid. Only cyanogen chlo- 

 rid and chloro]ncrin give promise of being useful for fumigation 

 purposes. Neither of these war gases, however, can be used in green- 

 house fumigation because of their injurious action on plants. Never- 

 theless, they probably will prove to be of value in the fumigation of 

 stored products. 



In Department Bulletin 866, Pickering Sprays, are published the 

 results of three seasons' experiments with types of sprays containing 

 smaller amounts of copper sulphate than standard Bordeaux mixture. 

 It was found that such spra3^s, containing from 0.6 to 0.7 per cent of 

 copper sulphate, controlled fungous diseases on potatoes and cran- 

 berries very effectively. Their control of fungous diseases on grapes 

 and apples was not definitely determined, the results being compli- 

 cated by burning or other injury to the foliage and fruit. It was 

 also found that sprays made with barium hydrate instead of with 

 lime were very successful as fungicides for potatoes. Increased 

 yields of tubers were obtained on plots of potatoes treated with Bor- 

 deaux and with a stronger Pickering spray, indicating that these 

 sprays exert similar stimulating and protective action on potato 

 plants. Moreover, the sprayed potatoes yielded tubers with a higher 

 amount of solids than those from unsprayed plots. 



One of the investigations upon spraying that has been in progress 

 for some years has been completed, and the results are being pre- 

 pared for"^ publication. This investigation was planned to deter- 

 mine how much of poisonous elements remain on fruits and vege- 

 tables sprayed with poisonous sprays, and also to cletermine how 

 such poisonous residues may be removed from the fruit or vegetable 

 to be marketed, and finally to determine the conditions of spraying 

 that would yield fruit and vegetables with the smallest possible 

 quantity of objectionable material remaining upon them as they 

 reach the hands of the consumer. 



The effect of the various compounds of arsenic on insects, includ- 

 ing bees, has been studied, and the manner of action of the various 

 compounds noted. It has been found that even insoluble arsenic com- 

 pounds seem to be soluble in the bodies of insects. This solubility 

 varies for different compounds and it seems possible to use certain 

 insects as indicators of the insecticidal value of arsenical compounds. 

 There are indications that the compound that shows the highest per- 

 centage of soluble arsenic in the bodies of these insects is the best in- 

 secticide with respect to killing property. The data are being col- 

 lected and analyses of bees will be made shortly. It is intended to 

 collect and tabulate all the cooperative data on the subject as soon as 

 the analyses are completed. It has also been found that a com- 



