GREENHOUSE RED SPIDER. 165 



obtain, while the price is rather high. In using this material on cucumbers 

 it is necessary to add soap to the solution in order to increase its spreading 

 qualities. 



Results. — This ^ray proved to be efficient in controlling actively 

 feeding mites, but only a few of those quiescent failed to molt. The eggs 

 were not affected. 



(b) Calcium Sulfid (CaS2). — This spray proved to be of little value 

 as it killed but few mites. Soap cannot be added to this solution as it 

 forms an insoluble calcium soap which is precipitated. Had this material 

 proved of value it could be obtained more cheaply in lime-sulfur, of which 

 it is a constituent, than in the form of the pure white calcium sulfid. 



(c) Sodium Sidfid (NajS). — To determine whether a substitute for 

 potassium sulfid could be obtained by the use of sodium sulfid, a spray 

 was made by the following formula: — 



Pounds. 

 Commercial NaOH, . . . . . . . . . • '^h 



Flowers of sulfur, . . . . . . . . • . .5 



After solution is complete add water to make 100 gallons of spray. 



Results. — Although this spray proved to be as effective in killing all 

 actively feeding mites as did the potassium sulfid solution, its effect on the 

 quiescent stages was materially less. The eggs were not injured. 



(d) Sohible Sulf^ir. — This is a commercial compound made up prin- 

 cipally of sodium sulfid, and as a spray the results check with those given 

 above, with the exception that this spray is very apt to injure the foliage. 



(e) Barium Sulfur (B. T. S.). — This material, used at the rate of 3 

 pounds to 50 gallons of water, is not injurious to foliage, but is inefficient 

 in controlling mites. Soap cannot be added, as it forms an insoluble 

 barium soap. 



(/) Lime-sidfur and Kico-jume Liquid. — This has been recommended 

 as a spray for spider mites as well as the clover mite (Bryobia), and has 

 the f ollomng composition : — 



Lime-sulfur, commercial (quarts), ........ 2 



Nico-fimie (pint), ........... i 



Water (gallons), ........... 25 



Results. — The application of this material caused considerable injury 

 to the cucumber foliage, while it was only fairly efficient in controlling 

 the mites. Several greenhouse men have sprayed -with dilute lime-sulfur 

 solution, but have found it both inefficient in controlling these pests and 

 injurious to the foliage. Nicotine sprays are also inefficient when used 

 alone. 



(d) Oil Sprays. 



1. Sprays containing Petroleum Oils, (a) Arlington Oil. — This is a 

 chemically miscible oil containing approximately 90 per cent, petroleum 

 oil. Used at the rate of 1 part oil in 50 parts of water it was found effective 



