70 MASS. EXPERIMENT STATION BULLETIN 233 



THE CHOICE OF FUNGICIDES AS AFFECTING THE CONTROL OF 

 DISEASE AND THE PREVENTION OF SPRAY INJURY 



Contributed by W. L. Doran, Department of Botany, 

 Massachusetts Agricultural Experiment Station 



As indicated by the spray calendar, most of the arsenic sprays for codling 

 moth control must also contain fungicides for scab control. 



A good fungicide for spraying apples must be one which will control 

 scab and cause no more than a minimum of spray injury when combined 

 with the necessary insecticides. Fungicides which have been used for this 

 purpose are liquid lime-sulfur, dry lime-sulfur, drj-mix sulfur-lime, sulfur 

 dust, and Bordeaux mixture. Liquid lime-sulfur is the cheapest of these. 

 It is dependable for the control of scab. It is used much more generally 

 than any of the others in Massachusetts. However, each has its virtues and 

 weak points with which the orchardist should be familiar. 



Bordeaux mixture controls scab but is not at all safe to use on the apple 

 because it so frequently burns or "russets" the fruit. 



Dry lime-sulfur may be used instead of liquid lime-sulfur, if desired. It 

 has been found to be the equal of liquid lime-sulfur for the control of scab. 

 The ordinary commercial dry lime-sulfur should be used at the rate of 8 

 pounds in 100 gallons of water. Either liquid or dry lime-sulfur in com- 

 bination with arsenate of lead may, under some conditions, injure the fruit 

 and leaves of sprayed trees. 



Dry-mix sulfur-lime or, as it is often called, Jersey dry-mix (see New 

 Jersey Agr. Exp. Sta. Circ. 177) may be purchased in the commercial form 

 cr may be made by the fruit grower. It is made by mixing the ingredients 

 together dry in the proportion of 16 pounds fine sulfur, 8 pounds hydrated 

 lime, and 1 pound calcium caseinate. Twenty-five pounds of this mixture is 

 sufficient for one hundred gallons of spray. Dry-mix sulfur-lime is less 

 likely to injure sprayed foliage and fruit than is lime-sulfur, and for this 

 reason it is sometimes substituted, especially for the calyx and later applica- 

 tions. In all except the most severe "scab years," Jersey dry-mix controls 

 scab satisfactorily. In rainy summers, when scab is severe, a somewhat 

 more complete control may be expected from lime-sulfur. 



The prevention of spray-injury is almost as important as the control of 

 certain insects and diseases. Spray-injury includes russeting of the fruit 

 and various degrees of burning and curling of the foliage as a result of the 

 application of the insecticide and fungicide. But there are certain other 

 troubles which are sometimes mistaken for spray-injury. Such injury may 

 occur, especially on trees lacking in vigor, regardless of whether or not 

 they are sprayed, if when the leaves are young a period of cloudy or rainy 

 weather is suddenly followed by drying winds and hot sunshine. Under 

 these conditions the edges or tips of the leaves may be burned. The identi- 

 fication of injury to foliage, due to the lime-sulfur-lead arsenate combina- 

 tion spray, is made easier by the fact that the injury, if it occurs at all, is 

 usually apparent two to four days after the applications are made. Spray- 

 injury, especially on the varieties Baldwin and Mcintosh, is common follow- 

 ing the use of the lime-sulfur-lead arsenate combination, and is most fre- 

 quently associated with the calyx and post-calyx applications. 



