- 4 - 



Stating these advantages cannot be done lightly without at once recognizing 

 the need for better understanding of the increasing number of chemicals. Such 

 diverse selection means varying response to different weather conditions, to 

 combinations with other materials in relation to compatibility, to variety dif- 

 ferences, etc. As a matter of fact, in the days of limited choices of fungi- 

 cides and insecticides, one could predict with considerable certainty the 

 results of simple combinations such as arsenate of lead and sulfur. In other 

 vjords , injury to foliage or fruit, although admittedly not occurring so often, 

 still may happen as a surprise and is not always easy to explain. 



Accordingly, the economics of pest control demands a very good balance of 

 judgment. Most growers will accept a little more outlay for materials that 

 will produce the result desired. Most are not inclined to omit a spray if there 

 is reasonable doubt about the feasibility of doing so. This decision cannot be 

 mathematical, for one can suffer much more in actual loss and down-grading of 

 fruit than can possibly be saved by leaving out one application. A fallacy in 

 figures that is too frequently presented is gauging the percentage of control 

 to the operation. For instance, 90 percent control cannot be set as a point 

 of attaining the most profit. Nor can this be set at 75, 80 or any other per 

 cent. On paper, hoii/ever, it is possible to produce figures of diminishing re- 

 turns above a certain point. The trouble is that pest damage often occurs so 

 quickly that the stopping point in percentage cannot be accomplished short of 

 disaster. 



All of this does not mean, nevertheless, that one cannot achieve pest con- 

 trol effectively and still inject efficiency and practical saving into the job. 



Emphasis should be placed on dosing correctly. Those who feel that "if a 

 little will do good, drastically increasing the mixture strength will do better" 

 waste money. They also increase chances for foliage and fruit injury and 

 damage to fruit finish. The residue problem is increased. With concentrating 

 of materials more or less common, it has become increasingly important to 

 figure dosage accurately. 



The operation of the equipment can affect greatly the cost of pest control. 

 Applying too much can have the same results as indicated with mixing too strongly. 

 On the other hand, poor results will occur if the mixture is too weak or the 

 application too light, not distributed well and generally not thorough. With 

 air blast sprayers, accuracy in operation pays in money. Gallons per tree is 

 the index and observing the coverage in application and deposit comprise the 

 check. All are essential--tractor speed, nozzle capacity and nozzle arrange- 

 ment and adapting the rig to the job. Substantial checking as the season starts 

 and as conditions change during the season will go far towards accurate, effi- 

 cient operation of the rig. 



For setting up the air blast sprayer for proper delivery this formula has 

 been used effectively over the years. It will bear repeating here. 



Gallons per minute per Rate of travel in One half of dilute 



X gallonage 



sprayer side feet per minute (F) required per tree (G) ^ 

 equals 



required for average tree X concentration Average tree spread in feet (S) 



X or 



in block at given speed desired Distance between trees (D) 



