10 B.C. Ento.mological Society. 



(2.) For some one or more reasons not clear to us, tmr kuowleilye of spraj's and 

 their effects is very unsatisfactory. 



(3.) Wliile our commercial insecticides are more or less stable, under certain 

 ideal conditions the results obtained from their use are too variable for us to make 

 definite and well-defined recommendations. 



(4.) The economy of spraying and the uumerous new sprays ou the market at 

 the present time demand an entirely new investigation of the subject. 



Outline of Experiments. 



With these facts in view the following series of experiments have been out- 

 lined : — 



(1.) Knowing that certain sprays are effective when used alone, to determine 

 what ones may be successfully combined without lessening insecticide values. 



(2.) Having effected the combination of certain sprays, to determine, if possible, 

 the factors that govern successful application with a miniuiura of injury to fruit and 

 foliage and at the same time give a maximum of protection. 



Combination Sprays. 



During the last few years the economy of proper plant-protection has become a 

 problem of great importance to the farmer and fruit-grower. We have well-known 

 insecticides and fungicides which are quite effective in the control of different pests, 

 but in order to be effective they mu.st be applied at the proper time. Every pest has 

 a distinct life-history method of development and manner of attacking its host or 

 hosts. These factors in most cases determine the method of treatment and time of 

 application. 



In former years the number of standard sprays for insect pests or fungous dis- 

 eases was very limited, and combination or mixed sprays were practically unknown. 

 With the development of the fruit-growing industry the number of important pests 

 increased, and at the same time more elaborate methods of control became necessary. 



The time of application of a spray for a fungous disease often coincides with the 

 time of application for some one or more important insect pests. This has led to 

 many experiments in the combining of insecticides and fungicides to determine the 

 practicability of applying two or more sprays at the same time, instead of making 

 separate applications of each. Considerable success has resulted from these experi- 

 ments, and the combining of a fungicide and an Insecticide or two insecticides is now 

 a common orchard practice of considerable value to the fruit-grower. 



However, many complications have arisen in the work, and while many general 

 conclusions have been upheld, combination sprays are very unstable and many details 

 are yet to be worked out. The greatest difliculty arises from the fact that arsenic 

 is the base of nearly all poison insecticides. Free arsenic will cause great injury to 

 foliage, and in order to use it some insoluble compound is necessary. In the form 

 of lead-arsenate, when jjroperly prepared, arsenical sprays can be applied with a 

 reasonable degree of safety, but in combination with other compounds the nature of 

 the original arsenical may be easily changed and free arsenic liberated. A very 

 important factor is also found in that lime-sulphur and Bordeaux mixture, the two 

 most important fungicides, are liable to cause spray injury when used alone, and 

 arsenates or arsenites are very apt to accentuate this danger. Climatic conditions 

 are also supposed to enter more or less into the serious injury that sometimes 

 happens from the use of these sprays. 



Some experimenters have claimed that in the combining of lime-sulphur and 

 arsenates of lead certain chemical reactions take place which impair the efficiency 

 of both. As there seemed to be no published data on experiments which might throw 

 light on this subject, the Dejiartments of Plant Pathology and Entomology of the 

 Oregon Agricultural College undertook in 1912 to make a series of experiments 

 ■svhich would at least show some indication as to the relative combative effects of 



