348 



reaction under the conditions is not quite so simple as supposed, for 

 ammonia is produced and a good deal of wet, acid spray distributed 

 over the plants and also on the tents, which suffered considerably. 

 The second method may be called the external, and consists in the use 

 of a special generator outside the space to be fumigated, the gas being 

 conveyed by a hose. Special generating machines are described in 

 this article, with reports on the results of their use, and it is claimed that 

 there is a great saving of time and greater uniformity and eflficiency. 

 while no damage is done to the tents and there is also a great saving of 

 labour and less risk. Improvements in construction will however be 

 necessary, as there is a good deal of corrosion of working parts ; but 

 the method is regarded as having great advantages over the pot 

 system. 



Branigan (E. J.). Vedalia vs. Icerya on Pears. — MtJtly. Bull. Col. 

 State Commiss. Hortic, Sacramento, iv, no. 2, February 1915, 

 pp. 107-108, 2 figs. 



During the past two years there have been frequent complaints of 

 serious damage to pears by Icerya purchasi (the cottony cushion scale), 

 and for some reason the Coccinellid, Novius {Vedalia) cardinalis, which 

 was supplied to growers, did not readily attack the scale when breeding 

 upon pears. During 1914, the problem became so serious as to threaten 

 the pear industry in certain localities. The black smut from the 

 honeydew made it necessary to go to the great expense of washing the 

 fruit, and this is not only costly but reduces its quality. Recently 

 the author, being in the infested locality, investigated this apparent 

 aversion of Novius for Icerya on pears. The explanation appears to 

 be due to the constant spraying of the pears for codling moth with 

 arsenate of lead, which saturates the young scales and egg-masses 

 with the poison and is fatal to both larval and adult Novius. This 

 prevents their control of scale on pears, while they control the scale in 

 the same vicinity when on plants other than pear trees. In the 

 laboratory, some Novius were confined on unsprayed scale-infested 

 pear and citrus twigs, and these fed quite as readily upon the pear- 

 infesting scale as on the citrus ones. Novius cannot therefore be 

 used as a control against the scale on pear trees, but as pears cannot 

 be successfully grown without spraying for codling moth, I. purchasi 

 must therefore be controlled by some artificial means. Neither spray- 

 ing nor fumigation has as yet proved sufficiently effective against it. 

 Perhaps Lestophonus and Ophelosia, the two internal parasites of 

 Icerya, may prove of value in this instance. 



Insect Notes. — Mthly. Bull. Cal. Stale Commiss. Hortic, Sacramento, 

 iv, no. 2, February 1915, p. 116. 



The adults of Diabrotica soror, Lee. (western twelve-spotted cucumber 

 beetle) were seen in great numbers hibernating among the dry weeds 

 along a levee in Yolo County, in January 1915. Lygus pratensis 

 (tarnished plant bug) was common in the same place. Aphis avenae 

 (European grain aphis) is threatening barley. During the summer, 

 considerable damage was done to the leaves of bay trees by Trioza 

 alacris (laurel Psylla) ; in November, when some of the worst infested 



