Control Measures 217 



bordeaux. There have been years when certain fields 

 have shown no increase from spraying, but usually a suffi- 

 cient increase has been obtained, if the spraying has been 

 well done, to pay for the cost of the applications. Even 

 in years when the blight is absent, the application of bor- 

 deaux appears to stimulate the vines, for they are greener 

 and remain alive longer than unsprayed vines. Bordeaux 

 also acts as a repellant to the flea-beetle and reduces the 

 amount of tip-burn and so protects the leaves from vari- 

 ous injuries. In years when blight is present, the evi- 

 dence is greatly in favor of spraying. One cannot tell 

 with any certainty when blight will come, so one should 

 practice spraying as a protection. Growers should accept 

 the evidence and make spraying of potatoes with bordeaux 

 a general farm practice every year whether wet or dry on 

 both early and late varieties. 



Preparation of bordeaux mixture (See Plate XIII) 



Bordeaux mixture can be purchased on the market as 

 a paste or powder. Usually most of the proprietary mix- 

 tures contain in addition an arsenical poison for killing 

 biting insects. They are prepared for spraying by the 

 simple addition of water to a given quantity of material. 

 For this reason they are convenient to use and also safer 

 when one needs to depend on irresponsible help to do the 

 work. However, these do not stay in suspension as well 

 as bordeaux properly made at home, and they are more 

 expensive. Home-made bordeaux, according to most 

 comparative experiments, is the most satisfactory. Its 

 preparation is easy and inexpensive and one requires but 

 a short time, when the apparatus for making it is once 

 constructed. The following directions with a few addi- 



