376 



Owing to lack of detailed information no effective control measures 

 have been found, but all infested plantations should be coppiced and 

 burnt over. 



In September pupation took place in fallen leaves, and the under- 

 growth was swarming with emerged moths, but in January 1921 no 

 trace was found of living pupae, and it is probable that the last brood 

 had not survived, either because it had been starved, or had been 

 exterminated by other influences. Numerous pupae of parasitic flies 

 were found among the cocoons. 



Chermes coolcyi. — Forestry Commiss., London, Leaflet no. 2, April 

 1921, 3 pp., 1 fig. 



Chermes cooleyi, Gill., which attacks Douglas fir and Sitka spruce 

 in America, has now been introduced into Great Britain, where at 

 present it has only been observed on Douglas fir [R. A.E., A, viii, 423]. 



Nursery plants of this conifer can be cleared of this gall Aphid in 

 autumn and winter by dipping them in a solution of 1 lb. soft soap 

 and 1 gal. water. If dipped in bundles the plants should be loose 

 enough to allow the liquid to reach individual needles. The solution 

 should not touch the roots. The plants should then be suspended, 

 roots uppennost, to drip for from one to five minutes. Even if only 

 isolated plants in nursery beds are infested, the whole bed should be 

 treated. 



LouNSBURY (C. P.). Cyanide Gas Remedy for Scale Insects. — //. 



Dept. Agric. Union S. Africa, Pretoria, ii, no. 5, May 1921, 

 pp. 437-452, 12 figs. 



The process of fumigating citrus trees with hydrocyanic acid gas 

 as a remedy for red scale [Chrysomphalus aurantii] and other " hard " 

 scale-insects is described. Details are given of the materials to be 

 used, the kind of generating vessel that is suitable, and the best sort 

 of cloth for covers. Improved methods of generating the gas, and 

 the various kinds of poles and their adjustment are discussed, with 

 illustrations. The proportions of the chemicals used in a charge 

 should be 1 oz. by weight of 126-130 per cent, sodium cyanide and 

 Ijoz. by measure of 94 per cent, (or higher) sulphuric acid to 2 oz. 

 by measure of water. The basis for calculating dosage is explained 

 and a standard dosage table is given. 



Treatment should be carried out in the absence of sunlight, pre- 

 ferably at night. It should be stopped if the wind is strong enough 

 to sway the covers or if the covers become too heavy with dew to 

 handle. The covers are far more gas-tight in damp air than in very 

 dry air or sunlight ; this explains in part why trees are more injured 

 on some nights than on others. Late summer and autumn are the 

 best seasons for fumigation work, and heavy dosages should be used 

 only at these times. The gas is said to do much injury to trees that 

 have been sprayed with Bordeaux mixture within several months. 

 Gas generated in the ordinary way acts best on the higher parts of 

 the tree [cf. K. A.E., A, vii, 228 ; viii, 29]. As scales on branches near 

 the ground are the most likely to escape the gas, it is advisable to precede 

 fumigation by trimming away any branches that rest on the ground 

 or that would be pressed to the ground by the cover. When killed 

 by fumigation, the scales remain on the tree in a dried condition 

 until scraped off or removed by wind or rain. 



