19201 ECONOMIC ZOOLOGY — ENTOMOLOGY. 755 



prove that insects may spread tlie urediiiiospore stage from bush to bush. It 

 is l)elievc(l that while the spread of C. ribicola from pine to Kibes or vice versa 

 may be infrequent or accidental, the spread of the uredinial stage upon Kibes 

 probably occurs with considerable regularity. 



Piue rust control, II. Hesselman (Slatcns SkogsforxokHanst., Flyybl. 15 

 (1919), pp. 8, figs. If). — This deals with the question of controlling pine rust 

 iPcridermium pint) under different conditions and on pines of widely varying 

 ages. 



A brief report of the proceedings and recommendations of the Inter- 

 national White Pine Blister Rust Conference for Western North America, 

 1919 (CorvalUa, Ornj.: Aincr. Plant Putholugists Ad. Bd. Rpt., 1919, pp. //).— 

 This account with dis-cussion of the work of this conference, which was held 

 in Portland, Oreg., Ai)ril 23 and 24, 1919, under the auspices of the Advisory 

 Board of American Plant Pathologists, includes the recommendations adoptetl. 



An outbreak of Trametes pini in a forest of maritime pine, F. Guiniee 

 (Bui. Soc. Path. Vcg. France, 6 (1919), No. 3, pp. 42, 48-51).— An account is 

 given of widespread attack on maritime pine (Piniis pinaster) by T. pini, in 

 parts of France. 



ECONOMIC ZOOLOGY— ENTOMOLOGY. 



Insecticide investigations, A. L. Lovett (Oregon Sta. Bui. 169 (1920), pp. 

 55, figs. 6). — This is a report on the progress of an investigation of insecticides 

 under way at the Oregon Experiment Station, which was commenced in 1914 

 and has been in part previously noted (E. S. R., 37, p. 759). The work has 

 shown that the acid salt, or lead hydrogen arsenate, has a higher killing effi- 

 ciency at a given dilution than either the neutral salt (basic lead arsenate) or 

 calcium arsenate. 



"All the arsenic devoured by caterpillars feeding upon sprayed foliage is not 

 assimilated, a portion passing through the digestive tract in the excrement. 

 The proportion assimilated is higher where an acid arsenate is employed. 

 This accounts for the higher killing efliciency of the acid lead arsenate. . . . 



" It requires approximately 0.1595 mg. of arsenic pentoxid to kill 1,000 small 

 tent caterpillars, and approximately 1.84 mg. of arsenic pentoxid to kill 1,000 

 nearly mature tent caterpillars, irrespective of the particular arsenate used as 

 a spray. A dilution of 1 : 400 of lead hydrogen arsenate proved a satisfactory 

 killing dosage for the very small caterpillars." 



" Under laboratory control conditions a dilution of 1 lb. of the acid lead 

 arsenate to 400 gal. of water proved an effective killing solution for very small 

 tent caterpillars. It is reasonable to assume that new>y hatched codling-moth 

 larvjB are no less susceptible to poison. 



"The commercial lead arsenates on the market, unless specitically iirepared 

 and labeled otherwise, are nearly pure acid lead arsenate. The powdered lead 

 arsenates are physically superior to the paste forms and are generally the 

 advisable form to use. Particularly is this true if one is not near the point of 

 manufacture, so as to insure a freshly made paste which has had no opportunity 

 to dry out or freeze. Allowing for the natural factors which render ideal 

 control conditions impossible in commercial orchard spraying, the apparent 

 discrepancy between the theoretical killing dosage of arsenate and the standard 

 dosage in vogue is due in part to physical defects: (a) In the methods of ap- 

 plication of spray; (b) In the spray solution; (c) in the spray material. Com- 

 mercial lead arsenates are in general a standard product. They vary but 

 slightly in the percentage of arsenic carried or in the low percentage of soluble 

 arsenic present. 



16032°— 20 5 



