87 



Carsner (E.). Susceptibility of various Plants to Curly-top of Sugar 



Beet,— Phytopathology, Baltimore, ix, no. 9, September 1919, 

 pp. 413-421, 7 figs. 



Various experiments have been made to determine from whence 

 the leaf-hopper, Eutettix tenella, Baker, obtains the virus of curly-top 

 disease of sugar-beet in the spring. Although the insect has been 

 known to retain the virus for 58 days when fed on non-susceptible 

 plants, it cannot retain it during the whole winter. Observations 

 show that the red stem filaree, Erodium cicutarium, which appears 

 soon after the winter rains, is accessible to the leaf- hopper as food and 

 for breeding. The disease apparently overwinters in this plant, from 

 which it IS transmitted to beet in the spring. 



Snell (W. H.). Observations on the Relation of Insects to the Dis- 

 semination of Cronartium ribicola. — Phytopathology, Baltimore, 

 ix, no. 10, October 1919, pp. 451-464. 



These observations show that although the spread of Cronartium 

 ribicola by means of insects from pines to Ribes and vice versa is 

 comparatively rare and accidental, the spread of the uredinial stages 

 upon Ribe^ probably occurs with some regularity. A beetle, Serica 

 sericea, feeding on a red currant bush was found to have aeciospores 

 on its body, and the sawfly, Neodiprion pinetum, has been found 

 on Ribes and is known to feed upon Pinus strobus. 



Stone (R. E.). Kerosene Injury to Shade Trees.— Phytopathology, 

 Baltimore, ix, no. 10, October 1919, pp. 476-477. 



Between 1917 and 1918 many shade-trees, especially maple, were 

 dying from an apparently imknown cause. Subsequent investigations 

 showed that three years previously in order to prevent the caterpillars 

 of the tussock moth [Hemerocampa] from crawling up the tree- trunks 

 bands of cotton wool had been placed round them and saturated on 

 several occasions with kerosene, the surplus oil being allowed to run 

 down the trunl^s. It is considered evident that this was the cause 

 of the damage. 



Hopkins (A. D.). The Bioclimatic Law as applied to Entomological 

 Research and Farm Practice.— Separate from Scientific Monthly 

 l^ne loco], June 1919, pp. 496-513, 3 figs. 



The bioclimatic law is founded on the determined country- wide 

 average rate of variation in the time at which periodical events occur 

 in the seasonal development and habits of plants and animals at 

 different geographical positions within the range of their distribution. 

 Other things being equal, this variation is at the rate of 4 days for 

 each degree of latitude, 5 degrees of longitude and 400 feet of altitude. 

 Owing however to topographical variations, as well as those of soil 

 conditions and weather, etc., a greater or less departure of the actual 

 from the computed date of a periodical event for a given place is 

 often found. The amount of this is in direct proportion to the 

 intensity of the controlling influences, which can therefore be measured 

 in terms of days or the equivalent in degrees of latitude or feet of 



