509 



Lees (A. H.). Some Aspects of Spraying against Pests. — JJ. R. Hortic, 

 Soc, London, xlii, no. 2-3, September 1917, pp. 213-228. 



The bulk of the matter in this paper has already been noticed [see 

 this Review, Ser. A, iii, p. 286, v, pp. 173, 360, 362]. The physical 

 means of controlling the chief pest% which occur in the egg-stage on 

 fruit trees, by the application of hot water, has been found 

 impracticable in the English climate under outdoor conditions, as 

 forcing the water through a fine nozzle reduces its temperature to a 

 point below that at which it coagulates the egg-contents. Chemical 

 treatment ^\^th penetrative oily bodies, such as nitrobenzine or paraffin, 

 has also proved a failure, as it damages the buds when the substance 

 is used of a strength sufficient to kill the eggs. Experiments made 

 ^vith commercial bleaching powder, which is an impure hypochlorite 

 of calcium, showed that eggs were unaffected by the strongest 

 solutions, but when caustic soda was present as well they were attacked 

 in a time varying from 10 to 40 minutes. The difficulty of keeping 

 them moist with a spray fluid for so long was overcome by using a 

 lime wash as a base, the eggs being found dead and shrunken on its 

 removal. It was proved that bleaching powder and lime or caustic 

 soda and lime have no lethal effects, all three substances requiring to 

 be present together to obtain success. The eggs of moths were found 

 to be most easily destroyed, then those of apple-suckers [PsyUa], and 

 Aphids ; those of red-spiders seemed to be quite unaft"ected. The 

 action appears to be, first the partial dissolution of the chitin of the 

 egg-shell by the hypochlorite, followed by the penetration of the 

 alkali to the egg-contents, causing coagulation of the albumen. 



Adams (J. J.). Disease and Insect Pests. — Ann. Rept. 1915-191G 

 Dept. Agric. British East Africa, Nairobi, June 1916, pp. 44-47. 

 [Received 20th September 1917.] 



Young lemon trees in the stock nursery were affected by citrus 

 psylla [Trioza], which was however kept in check by the use of 

 Cooper's V2 fluid. A one-year-old Tahiti lime tree that was covered 

 with scale-insects was painted all over with lime-sulphur wash — 40 to 1 

 mixture — only one application being necessary to free the tree of this 

 pest. A small yellow beetle appeared in large numbers at the beginning 

 of the rainy season doing great damage to all plants and trees. The 

 action of rain rendered spraying A\ith arsenate of lead and Paris green 

 ineffective, lime-sulphur proving only slightly more adherent, while 

 small fires of weeds and rubbish emitting dense volumes of smoke 

 cleared the trees but did little harm to the beetles. Plums and peaches 

 were sprayed for fruit-flies with lead arsenate, once just after the 

 fruits were formed, and again when half-grown, with satisfactory 

 results. Some trees in various districts were very badly infested with 

 the citrus red scale, CJmjsomjjhalus [Asjjidiotus) aurantii, which is 

 most difficult to control, and planters should purchase trees only from 

 nurseries that have passed the Government Entomologist's inspection. 

 The only remedies are the painting of the whole tree, if young, with 

 resin wash, or, in the case of large trees, fumigating with hydrocyanic 

 acid gas. 



