PESTS AND DISEASES OF PLANTS 223 



Mix these ingredients thoroughly and apply with a power blower. 

 This is one of the. most efficient preparations now being used in con- 

 trolling the red spider of deciduous trees. 



Milled Sulphur. 



This is sulphur to which something else is added to make it possible to 

 grind it exceedingly fine. It is known by the trade names, atomic sulphur 

 and diatomic sulphur. It is very good for red spider and mites. 



Pyrethrum. 



This is commonly known as Persian or Dalmatian insect powder, or 

 Buhach, and comes as a finely ground yellow powder with a pleasant, 

 rather pungent odor. Unfortunately it is not only expensive but quickly 

 loses its effectiveness when exposed to the air. Its practical range is 

 therefore limited, and it is chiefly used on house plants, in the conservatory 

 and in the garden. It is entirely harmless to vegetation of all kinds and 

 does not spot or mark even the most delicate flowers when used dry. It 

 acts a little more promptly and effectively if applied to the insects while 

 they are moist, or at least damp. If the dusty appearance is objectionable, 

 a decoction may be made by steeping one ounce in one quart of boiling 

 water, and then adding two or three quarts of cold water. Into this 

 material potted plants may be dipped, or it may 'be applied with an 

 atomizer. For plant lice on house plants this makes a very clean and 

 effective application. 



Hellebore. 



Powdered white hellebore has been used for many years as a specific 

 remedy against "currant worms," "rose slugs" and other saw-fly larvae, 

 and is very effective, either dusted on as a powder, or in the form of a 

 decoction. When applied, it may be used pure, or it may be mixed with 

 two or three times its own weight of dust, cheap flour, lime, or almost 

 any other light, finely powdered material. When used as a spray, steep 

 one ounce in one quart of boiling water and add another quart of cold 

 water when ready to apply. 



It is also quite effective against certain root maggots, like those 

 affecting cabbage and cauliflower. For these it is used in the form of a 

 decoction, one ounce in one gallon of water and about half a pint poured 

 around an infested plant, from which the earth has been drawn away to 

 facilitate soaking directly around the plant. To be effective, the material 

 must be brought into direct contact with the insects. Hence, it should be 

 liberally used and applied before the maggots get down too far, or into 

 the plant too deeply. In the garden its use is quite practical; in the field 

 it has not been found so satisfactory. 



REPELLENTS. 



It is apparent that certain materials, applied to the foliage of plants, 

 are somewhat repulsive to some insects. One of the most important of 

 these repellents is the well known fungicide, Bordeaux mixture. 



