158 EXPERIMENT STATION RECORD. 



procedure with field and truck crops and usually will prevent serious infesta- 

 tion, although there are some exceptions to the rule. 



" Crop rotation I'romises to be u good procedure in certain instances, although 

 much care should be exercised in selecting a crop that either matures early in 

 the season before serious mite attaclis or is quite resistant to the mites. Trap 

 crops, banding, and irrigation are of questionable value. Fumigation is not 

 effective. This appears to be due to a general resistance of arachnids to poison- 

 ous gases which is correlated with the difference in their system of respiration, 

 from that of insects and some of the other arthropods. Spraying in general, 

 while it will kill a large percentage of the mites if properly done, will not give 

 as satisfactory results as it will with most insects. It is especially troublesome 

 as it must be done in the heat of the summer, and is expensive since two appli- 

 cations must be made. Dry sulphur has a very limited use on account of de- 

 pendency upon weather conditions for effectiveness. Nicotin and emulsion 

 sprays are preferable to the sulphur and lime-sulphur sprays. The latter are 

 at times of questionable value. Adhesive sprays will not always give success; 

 they probably are effective under certain local conditions. The free use of water 

 as a spray is to be reeommende<l, as it knocks many mites from the leaves, so 

 injuring them that they do not return; it lowers the temperature and in this 

 manner reduces the rate of reproduction among the mites ; it checks migrations ; 

 and finally, it favors the multiplication of predaceous mite enemies. The paint- 

 ing of sulphur on the steam pipes in greenhouses, and the throwing of handfuls 

 of sulphur in the crotches of trees, although both are practices time honored 

 and entrenched by custom, should not be followed. They are useless and ex- 

 pensive and give no relief from mite attacks." 

 A bibliography of 01 titles is appended. 



[Spraying tests of insecticides upon potatoes], J. W. Inge {North Dakota 

 Sta. Spec. Bui., 3 {IDlJf), No. 9, pp. Ufl-lol). — This is a report of a preliminary 

 series of potato spraying tests with insecticides, fungicides, and " stickers." 

 There were 150 small plats of potatoes under observation, all sprays being 

 applied four times, about two weeks intervening between sprayings during the 

 season. The results are dealt with under the headings of (1) adhesiveness, 

 (2) effect upon the plant, (3) effect upon insects, (4) effect upon blight, (5) 

 effect upon maturity, and (6) effect upon yield. 



" Lead arsenate and zinc arseuite were s-hown to be greatly superior to Paris 

 green in the power of adhering upon the plant. There was also an apparent 

 increase in sticking power produced by the addition of soap and glue and the 

 carbonates of either iron, lead, or zinc. Even slaked lime and flour seems to 

 increase the adhesive property of sprays. ... It was shown in a very striking 

 manner that sulphur sprays are not satisfactory for potatoes. In every case 

 where lime-sulphur, ' soluble sulphur,' and ' sulfocide ' were used in combination 

 with the arsenicals, the foliage was badly burned at every application and the 

 plants never fully recovered. The sulphur comiX)unds with Paris green seemed 

 to be even more caustic in their action upon the plants than with the lead 

 arsenate. . . . With a few exceptions the beetles invariably avoided the ar- 

 senical sprayed plants and the slugs which started to work upon the vines were 

 very few in number and quickly killed. From the tabulated data it would seem 

 that certain fungicides, as lime-sulphur, and the carbonates and hydroxids of 

 zinc, copper and manganese, exerted a repressive action upon the slugs. . . . 

 The combination of arsenicals and fungicides seemed to be quite effective in 

 prolonging the life of the vines." 



Preparation of nicotin extracts on the farm, W. B. Ellett and J. T. 

 Grisso-M (Virginia St a. But. 20S (lOl-'t), pp. 3-16, fig. 1).— The investigations 



