February, '22] brittain: the apple sucker 99 



The Treatment of Nursery Stock. The necessity of finding some 

 suitable treatment to be given imported nursery stock known to be in- 

 fested or suspected of being infested with the eggs of these pests, is 

 one that occurs immediately to any official entomologist. 



Fimiigation with hydrocyanic acid gas carried on in exactly the same 

 way as for the San Jose Scale, with exposures varying from 1 hour to 

 10 hours, have been conducted for the past two seasons. Those during 

 the past season, though on a much larger scale then the previous one, 

 are far less satisfactory, because not only a very large percentage of 

 eggs failed to hatch on our check trees, but the hatching was also very 

 irregular. 



However, the final result of all our work is to show that while a single 

 hour's exposure to hydrocyanic acid gas destroys a very large percentage, 

 and in some cases all, of the eggs, some individuals have survived an 

 exposure of nine hours to the same strength of gas. The indications are, 

 however, that spring fumigation is more eftective than fall fimiigation. 

 It may be said that other fumigants such as carbon tetrachloride, even 

 at prolonged exposures, failed to give satisfactory results. 



Dipping the stock in various solutions was also attempted. In some 

 cases we secured perfect results with certain of these mixtures, but in 

 others under exactly the same conditions, a few individuals came through 

 unharmed. As was the case with fumigation, the spring treatments 

 were more effective than the autumn treatm.ents, but the only material 

 that gave perfect results spring and fall was 5% (by volimie) emulsion 

 of carbolineiim. The liability of this compound to injure the buds, 

 however, makes it doubtful whether it will ever find favor for this pur- 

 pose, unless some one can devise a stable product of constant composi- 

 tion, and of equal value as an insecticide, which will, at the same time, 

 be harmless to the trees. Furthermore, dipping as a means of treating 

 imported stock has many disadvantages, as compared with gas treat- 

 ments. Not only is it very laborious, unpleasant, and not adapted to 

 large shipments, but it leaves too much to the individual carefulness 

 of the operator. Even should some treatment be found that proved 

 effective in careful hands, it is a question whether this method would be 

 adopted b}^ any govemm_ent as a means of treating imported stock. 



Orchard Treatments. The control of the insect under orchard 

 conditions may again be subdivided into (1) treatments directed against 

 the egg or hatching young, (2) treatments directed against the nymph 

 and (3) treatments directed against the adult. 



1. For dormant spraying we have obtained best results, so far, by 

 spraying with the lime and salt wash recom.mended by Theobald (In- 

 sect-Pests of Fruit, p. 162, 1909), consisting of 100 lbs. lime and 30 



