469 



upper and lower surfaces of the leaves is negligible. WTiere insects or 

 fungi had produced holes in the leaves, spray injury was observ-ed 

 around the edges of these holes, but if the rest of the leaf was not 

 affected such injury was not rated as injury by spraying. Injury did 

 not usually appear until a week after spraying, increasing in severity 

 later, but in general the final degree of injury had been reached after 

 about 12 days. Pear and elm proved the most resistant of the trees 

 used in the experiments ; apple came next, but was much less resistant ; 

 then came cherry, Bradshaw plum and peach. No injur}^ either from 

 the pure or commercial materials was obtained with a combination 

 of lower temperatures and humidities, but traces began to appear 

 as these factors becam.e higher. It was shown that with reasonably 

 good materials injury is caused by temperature, humidity and perhaps 

 hght, and an analysis of these effects proved that the neutral lead 

 arsenate used, though not entirely pure, was the safest material in 

 clear weather, and in most cases was better in cloudy weather than 

 the others. Clear weather spraying is safer than cloudy weather, but 

 the difference is not great. Spraying at high temperatures is safe if 

 the humidity is low, and at high humidities if the temperature is low, 

 though the humidity cannot run up as high as the temperature. The 

 experiments have failed to answer the question why arsenical sprays 

 sometimes injure foliage, but they have shown that some of the 

 explanations given can be rejected, viz., that the arsenic (ASgOg or 

 AS2O5) was present in the material uncombined with any base ; 

 that it was so loosely combined with the base as to become Hberated 

 during the addition of water in preparing it for application : or that 

 injurv was due to the presence of injurious impurities in the material. 



CoAD (B. R.), Tucker (E. S.), Williams (W. B.), Boxdy (F. F.) 

 & Gaixes (R. C). Dispersion of the Boll Weevil in 1921.— U.S. 

 Dept. Agric, Washington, D.C., Dept. Circ. 210, 23rd February 

 1922, 3 pp., 1 map. [Received 18th July 1922.] 



The cotton boh weevil [Anthononms grandis, Boh.] has now reached 

 the limit of cotton cultivation in the United States, except in western 

 Texas, south-western Oklahoma, north-eastern North Carolina and 

 Virginia. The situation in the various States is briefly outlined. In 

 all, 66,662 square miles of new territory were invaded b}- the weevil 

 in 1921, making a total of 600,771 square miles. About 105,000 square 

 miles of cotton territory are still uninfested. A map shows the spread 

 of the weevil from 1892 to 1921, and tables record the movement 

 of the pest in 1921 by States and the proportion of the cotton crop of 

 each State produced in uninfested land. Only 5-4 per cent, of the 

 crop from the cotton belt originates from uninfested land. 



iMiLBRATH (D. G.). Control of Diseases of Cucumbers in Greenhouses. 



— Mthly. Bull. Cal. Dept. Agric, Sacramento, xi, no. 5-6, 

 May-June 1922, pp. 430^37, 4 figs. 



The only insect pests dealt with are Aphis gossypii, Glover (melon 

 aphis), Diahrotica vittata, F. (striped cucumber beetle) and D. diiodecini- 

 piinctata, Oliv. (twelve-spotted cucumber beetle), which are carriers of 

 mosaic disease, and Heterodera radicicola, Greef, which causes root-knot 

 in the plants. 



Screening, periodical fumigation and the destruction of wild host- 

 plants of mosaic disease are recommended against the former and 

 sterilisation or removal of soil against H. radicicola. 



