117 



Herbert (F. B.). U.S. Bur. Ent. Results of Washing Experiments 

 for Control of the European Elm Scale. — Jl. Econ. Ent.. Concord, 

 N.H., xiii, no. 6, December 1920, pp. 471-475. 



Gossyparia spuria, Mod. (European elm scale) may be satisfactorily 

 controlled on small trees by washing with a garden hose and nozzle, 

 and an average force of water. During experiments at San Jose, 

 California, large trees were successfully treated by means of a 

 steam fire-engine and water from the large city mains, producing a 

 pressure of from 100 to 160 lb. to the square inch. An ordinar}^ orchard 

 spray outfit is advocated for trees up to 35 or 40 ft. high. This 

 method is slightly more expensive than washing, but it will probably 

 be more satisfactory. The best time for such operations is just before 

 the leaves unfold. At San Jose this was about 17th to 25th April 

 in 1918. 



WoGLUM (R. S.) & Rounds (M. B.). U.S. Bur. Ent. DayUght 

 Orchard Fum.igation. — //. Econ. Ent., Concord, N.H., xiii, 

 no. 6, December 1920, pp. 476-485. 



Further trials have been made to determine the possibility of success- 

 ful daylight fumigation with liquid hydrocyanic acid gas for the 

 control of scale-insects [R.A.E., A, vii, 288; viii, 29]. The most 

 suitable material to use for fumigation tents and the relative tempera- 

 tures under light and dark coloured tents are discussed, and tables 

 show the comparative results of night and dajdight fumigation on the 

 black scale [Saissctia nigra], and of the relative mortality in different 

 parts of a tree fumigated in the sunshine. 



Sunshine coming into contact with plants immediately after fumi- 

 gation, and before they have fully recovered their normal physiological 

 activity, is one of the most important factors as regards injury to the 

 tree. The strength of gas, the length of exposure and the temperature 

 or intensity of the sunshine are all considerations that form the basis 

 of daylight fumigation procedure. Injury from daylight fumigation 

 is characterised by dropping of the leaves, particularly on the sunny 

 side of the tree, and in severe cases by bleaching of green fruit. It 

 is noticed that lemons seem to be far less susceptible to sunshine fumi- 

 gation than oranges. 



As a result of experimental daylight fumigation carried on from 

 the middle of the active fumigation season in October throughout 

 the winter period, the authors are convinced that, where practicable, 

 daylight winter fumigation is preferable to night work. At this 

 period the scales are particularly diiBcult to kill on cool nights. 

 Moreover the trees are in a dormant condition and can withstand a 

 stronger gas, even at temperatures approximating 80° F. Particular 

 attention should be given to the exposure. It is not considered, 

 however, that the daylight practice can be recommended to supersede 

 night work, except in the case of experienced and careful operators 

 who can constantly manipulate the dosage and exposure. Fixed 

 doses and exposures are the safest, but the necessary data have not 

 3-et been accumulated to establish these ; in fact, they will be 

 difficult, if not impossible, to establish in the extreme varieties of 

 daylight weather during the usual fumigating season, and in view of 

 the widely differing conditions between the hot interior valleys and the 

 cooler, more humid coastal belt. 



