SCAB FUNGICIDES 



The following information about scab fungicides was obtained from various 

 sources and should be helpful in selection and use of materials in the disease 

 control program. 



Material 



RET. 



RED. 



*Infection time from beginning 

 of rain 



"1^5^ 



lo^ 



55^ 



60OF 



Captan 50% 2 lbs. 

 Dichlone 50% 1/2 lb. 



Dodine 

 **Ferbam 

 **Glyodin 



1/4 lb. 



65% 1/2 lb. 

 75% 1-1/2 lbs. 

 30% 1 qt. 



**Glyoxide 70% 10 ozs. 



Phenyl Mercury 



10% 1/2 pt. 

 10% 1/4 pt. 



**Sulfur 

 **Paste 



Thiram 



95% 5 lbs. 

 70% 7 lbs. 

 65% 2 lbs. 



Fair 

 Fair 

 Fair 

 Good 

 Very Good 

 Good 

 Good 



Good 

 Good 



Fair 



Good 



Fair 



Good 

 Fair 

 Fair 

 Good 

 Good 

 Poor 

 Poor 



Poor 

 Poor 



Good 



Good 



Fair 



40 hrs. 

 60 

 50 

 ? 

 20 

 20 

 20 



90t 

 60* 



24 hrs. 



48 



36 



28 



14 



14 



14 



72 

 48 



20 hrs. 



40 



30 



25 



11 



11 



11 



65 

 40 



18 hrs. 

 36 

 24 

 20 



9 



9 



9 



60 

 36 



20 

 20 

 36 



14 

 14 

 20 



11 

 11 

 18 



9 



9 



15 



RET. = Retention or the ability to withstand the washing action of rain. 



RED. = Redistribution or property of being washed around by rain to other parts 

 of the leaf or from leaf to leaf. 



Retention and redistribution are interesting properties. Obviously, the 

 most desirable combination is sufficient retention so the fungicide is not washed 

 off easily and at the same time some redistribution so the spray will wash to 

 parts where no spray was applied. These properties are difficult to evaluate for 

 scab control. For example, the retention of captan, when subjected to rain 

 washing tests in the laboratory, is only fair and yet, in the orchard, it gives 

 excellent scab control. The retention of ferbam is very good and much better 

 than captan and it also has good redistribution, yet it does not give as good 

 scab control as captan or thiram. Nor is it as good as glyodin which has good re- 

 tention but only poor redistribution. Again we repeat, the properties of retention 

 and redistribution are interesting but the performance of the fungicide in the 

 field is what counts. 



*Infection time in the table is calculated from the beginning of the rain and is 

 for the average temperature during an infection period. The hours in the column 

 for a given temperature are different for different fungicides. To be sure of 



4 



