450 Diseases of Economic Plants 



usually possible to combine the two so that only one applica- 

 tion is necessary. The stomach poison which is commonly 

 used for spraying tree fruits is lead-arsenate. It comes in two 

 forms, the powder and the paste. The latter contains 50 per 

 cent of water. The powder should be the fluffy, finely di- 

 vided kind. Either form may be used with Bordeaux mix- 

 ture or boiled or self-boiled lime-sulfur. The powder is vised 

 at the rate of 1 pound to 50 gallons of spray, the paste at 

 the rate of 2 pounds to 50 gallons. 



Paris green can not be used with lime-sulfur, at least in 

 spraying tree fruits, because of the resulting foliage and fruit 

 injury. When used with Bordeaux mixture for spraying 

 other plants it may be made up at the rate of 5 ounces to 

 each 50 gallons of spray. 



Calcium arsenate seems to be a promising stomach poison 

 for use with Bordeaux mixture or lime-sulfur. 



Nicotine preparations for the control of plant lice can be 

 used with lime-sulfur, or with lime-sulfur and lead arsenate. 

 There have been reports indicating that it should not be used 

 with Bordeaux mixture. 



Bordeaux injury. •'^^' ^^"' ^^^ — Many plants sprayed with 

 Bordeaux mixture assume a deeper color and are more 

 vigorous and live longer than unsprayed plants, even in the 

 absence of fungous attacks. The potato is a notable exam- 

 ple. Other plants are injured to a greater or less extent. The 

 peach, plum, sweet cherry, and apricot are so severely af- 

 fected by Bordeaux mixture that this fungicide is not used in 

 spraying them. 



Ever since the first trials of Bordeaux mixture upon the 

 apple, some injury has been noted upon both leaves and 

 fruit, due to the mixture itself. The amount of injury differs 

 with different varieties and with other conditions. Water, 

 deposited as rain or dew on the surface to which Bordeaux 

 mixture has been applied, is a necessary contributing cause. 

 As the season advances the foliage becomes more susceptible. 

 On the other hand, the fruit is most susceptible early in the 

 season. The most damage to the fruit occurs from the spray 



