282 



CONTROLLING INSECTS AND DISEASES 



ing^^ stages. Though its use is as yet experimental, it is pos- 

 sible that some of the pre-blossom sprays may be omitted if 

 Elgetol proves to be effective and desirable. 



(6) Consider Materials for Disease Control. Materials 

 used to control fungus diseases are termed fungicides. The 

 active agents in most of these materials are sulfur or copper. 

 Lime is commonly added to neutralize any caustic action that 

 might attend their use. Fungicides prevent germination of 

 the spores and the establishment of the fungus upon the host. 



b : 1. Lime-sulfur, or concentrated lime-sulfur, is used very 

 extensively for the control of fungus diseases. It is described 

 under "Contact Insecticides,^^ a : 5. 



In some sections its use has resulted in a burning of the 

 leaves and a russeting of the fruit. The advice of the experi- 

 ment station serving the section in which the fruit enterprise is 

 located is usually the best guide. 



b : 2. Bordeaux mixture is a combination in certain pro- 

 portions of copper sulfate (blue stone or blue vitriol), burned 

 lime or quicklime, and water. Thus a common formula is 

 1 1 50, i.e., 4 pounds of copper sulfate, 4 pounds of burned 

 lime, and 50 gallons of water. 



There is a decided tendency now in practice to include an 

 additional unit of lime as a further safeguard against burning. 

 Thus, 4-5-50 and 3-4-50 are common formulas among fruit 

 growers. 



Bordeaux mixture is a stronger fungicide than lime-sulfur 

 but under some atmospheric conditions may cause severe burn- 

 ing of fruit and foliage. Some varieties are more susceptible 

 than others. In apples, the greatest injury occurs while the 

 apple is young and held erect on the blossom stalk. It is evi- 

 denced by a russeting of the fruit and in severe cases by sub- 

 normal or abnormal development. Bordeaux mixture does not 

 seem safe as an apple spray in New England, New York, or 

 New Jersey. It is used quite extensively on apples in Nova 

 Scotia and in Virginia. 



