292 MASS. EXPERIMENT STATION BULLETIN 246 



Sprai/ing 



Below the temperature of 70° F. and in prevailing dull weather, sulfur dust- 

 ing materials do not give control. Mildew in contact with sulfur particles is 

 destroyed but that on the lower and sheltered parts of leaves is not affected. 

 When sucii weather conditions render sulfur dust of no value, spraying must 

 be resorted to for controlling the fungus. 



Both copper and sulfur spraying materials kill mildew but they are inju- 

 rious to foliage at strengths ordinarily used on other plants. At weak- 

 strengths they impart no harmful effect to the foliage and control mildew. 

 In the case of copper sprays, complete wetting of the foliage is important 

 since the action of the spray is exerted only when the fungus is wetted. After 

 the spray has dried, the copper residue offers little, if any, protection from 

 subsequent infection. Frequent treatments with copper sprays may be neces- 

 sary to maintain control. Freshly prepared Bordeaux mixture of the formula 

 1-1-50 or commercial copper preparations diluted to contain an equivalent 

 amount of copper are recommended. Slightly longer protection from infec- 

 tion is provided by sulfur spray residues, of which potassium sulfide made 

 up at t.lie rate of 1 pound to 50 gallons of water is tlie most satisfactory. 

 Bordeaux 1-1-50 leaves a slight residue which may require wiping the cucum- 

 bers before they are packed, while potassium .sulfide at the rate recommended 

 leaves none. Aside from this fact the use of either copper or potassium sul- 

 fide should be influenced by its compatibility with insecticides recommended 

 for controlling insects and red spider. 



Bordeaux mixture should be prepared as follows: 



As many pounds of bluestone as there are gallons of water are suspended 

 in a sack in the upper surface of the water in a wooden barrel. When the 

 crystals are completely dissolved eacli gallon will contain 1 pound of blue- 

 stone. Similarly, in a second barrel bim]> or granulated lime is slaked in 

 water. Slaking should proceed slowly with tlie addition of water as needed. 

 After the lime is slaked, tlie container is tilled witli water so that the mixture 

 contains 1 pound of lime to each gallon of water. Hydrated lime may be 

 substituted if lump lime cannot be obtained. Ciiemically hydrated lime is 

 considered the best, but if plasterer's or finishing lime is used it should be 

 soaked in water over night. One poimd of chemically hydrated lime, or IJ. 

 poimds of finishing lime will be required for each gallon of water. In the 

 making of Bordeaux 1-1-50, one gallon of stock lime water is drawn after 

 ligitating the mixture thoroughly and poured through a strainer into the spray 

 tank containing 30-40 gallons of water. While the agitator is running, 1 gal- 

 lon of stock bluestone solution is added. Water is then added to bring 

 the liquid up to 50 gallons. If larger or smaller quantities of spray are 

 desirecl, proportionate amounts of stock solution must be used. Separate pails 

 .'hould be used for drawing from the stock licpiids and a wooden ])ail should 

 be vised for the bluestone. The stock solutions will keep indefinitely but in 

 o^de" ^-hnt the nripinnl r-o^cpn'rn^^if^n nf one poimd of material to 1 gallon of 

 water is maintained, the barrels should be kei)t covered. 



Commercial co])per preparations may be substituted for freshly prepared 

 Bordeaux but they should not be diluted according to directions accompany- 

 ing the package since these are not applicable to hothouse plants. One pound 

 of bluestone present in Bordeaux 1-1-50 contains about 25 per cent of copper. 

 Each package of copper fungicide bears a statement giving the percentage of 

 copper present in the contents. To determine the amount of material required 

 for making 50 gallons of spray containing as nuich copper as is present in 

 Bordeaux 1-1-50, divide 25 by the per cent of copper indicated on the pack- 



