164 MASS. EXPERIMENT STATION BULLETIN 179. 



2. Soaj). — The addition of soap to a spray material increases its 

 spreading qualities and at the same time adds to its adhesive properties. 

 For red spider control soap is inefficient as a contact poison, but if used 

 in faii'ly concentrated solutions it proves to be an excellent adhesive 

 spray. 



Ivory soap used at the rate of 1-1 pounds in 25 gallons of water was 

 tried as a spray and found to be as effective as flour paste (8-8-100), with 

 the advantage of being much easier to make and not requiring constant 

 agitation. 



Results. — After this spray has been applied the water evaporates, leav- 

 ing a brittle film of soap over the mites, which is fairlv efficient in sticking 

 these pests to the leaves. However, nearly all mites which are in the 

 quiescent stage molt and establish themselves, and quite a few of the 

 actively feeding mites are able to break the brittle film of soap covering 

 their bodies and thus become liberated to feed on the leaf as before. The 

 eggs are not affected. 



A common brand of fish oil soap, at the rate of 1 pound in 10 gallons 

 of water, was applied to mites on cucumbers. The efficiency of this over 

 ordinary soap proved to be very little, if anj\ 



(c) Sulfur and Compounds of Sulfur. 



Sulfur and many of its compounds have been recommended for the 

 control of red spiders attacking various plants. The following have 

 been tried thoroughly, but have proved, for the most part, inefficient. 



1. Dry Sulfur. — In southern California, where the temperature is 

 high, dusting plants early in the morning so that the dew on foliage 

 will cause the particles of suKur to adhere has been found very suc- 

 cessful, especially upon low-growing plants. The use of resublimed 

 or flowers of sulfur on plaats which are not prostrate has proved very 

 unsatisfactory as a control for red spiders. Many of the market gardeners 

 of Boston have thoroughly tried out this method without any material 

 success. Several experiments were conducted, but dusting did not seem 

 to affect the red spiders in the least, even though the temperature was 

 high. 



2. Sulfur as a Liquid Spray. — This spray has been recommended for 

 controlling red spiders, but experimentally proves to be of very little 

 value. 



3. Sulfur Compounds, (a) Potassium Sulfid {Liver of Sulfur) KoS. — 

 This spray has been recommended by McGregor as being very effective 

 in controlling red spiders attacking cotton. Using 3 pounds of potassium 

 sulfid to 100 gallons of water, McGregor found that 100 per cent, of the 

 mites on cotton were killed by this spray. This is an easily prepared 

 material which may be a])plied ^vith safctj'' to foliage, but at the present 

 time, on account of the increasing demand for potassium salts for use in 

 the manufacture of munitions and fertilizers, this is very difficult to 



