295 



in thorough spraying is most apparent. So far as apple scab is con- 

 cerned, the work of 1914 produced results approximating to those 

 obtained in 1913. Dust mixtures, containing 10 per cent, of lead 

 arsenate, appear to be as effective as those containing twice that 

 quantity [see this Review, Ser. A, ii, p. 709]. The quantity of sulphur 

 applied per tree may be reduced without reducing the fungicidal value. 

 No satisfactory information was gained as to whether the addition of 

 an inert substance would improve the adhesive properties of the dry 

 mixture. Paste sulphur, although applied very cheaply, does not 

 seem to be the equal of lime-sulphur solution, though the test cannot 

 be regarded as conclusive. 



High (M. M.). Cactus solution as an adhesive in arsenical sprays for 

 insects. — U.S. Dept. Agric, Washington, B.C., Bull. no. 160, 

 22nd January 1915, 20 pp. 



Ojpuntia lindheimeri, Engelm., the prickly pear, is very mucilaginous 



and is invariably used by Mexicans in the manufacture of whitewash 



to promote adhesiveness. This suggested its use in preparing arsenical 



sprays against Diabrotica balteata, Lee. (the belted cucumber beetle). 



It is applicable for the treatment of insects of related habits, such as 



the striped and twelve-spotted cucumber beetles. Spineless cactus 



may be used, but the spiny variety appears to be nearly one-third 



richer in mucilage. If sliced at right angles to the spines, the cactus 



yields a higher percentage of mucilaginous matter and the time 



required for preparation is materially shortened. Large pieces are, 



however, best cut both ways, as this insures a more rapid and copious 



flow of the juices. The sliced cactus is placed in water in the evening 



previous to spraying, and the following morning the soUd particles are 



removed before the poison is added. The use of the regular " pear 



burner," or torch, which singes the spines, enables the cactus to be 



handled with ease ; only a short time is required to burn the spines 



from enough cactus to make sufficient adhesive material for several 



thousands of gallons of spray mixture. Cactus growing in low wet 



places yields less glutinous matter than that from high dry soil. The 



insecticides that have been employed in combination with cactus 



include lead chromate, Paris green, zinc arsenite (in both powder and 



paste forms), lead arsenate (paste), ferrous arsenate, and iron arsenite. 



With the exception of lead chromate, all these have been the subject 



of experiments described in this paper. The powdered zinc arsenite 



gave excellent results in every instance when used in combination 



with cactus water, and the mortality was in some cases higher than 



when three times the weight in paste form was used. Very favourable 



results were obtained with ferrous arsenate in most cases, while the 



results with iron arsenite were not quite so good. Iron arsenite has 



little insecticidal value unless an effort is made to apply it in uniform 



coating to the foliage. A comparison of whale-oil soap and cactus 



was instituted in order to test their respective value as adhesives, 



without considering their cost. Thirty-five pounds of sliced cactus was 



placed in 60 U.S. gallons (50 Impl.) of water in the evenng and had 



given up its glutinous matter by the following morning, when 1 lb. 



of zinc arsenite powder was added. One acre of cabbage was then 



sprayed with this mixture, which spread and adhered exceedingly 



