UNIVERSITY OF CALIFORNIA AGRICULTURAL EXPERIMENT STATION BENJ. IDE WHEELER, President THOMAS FORSYTH HUNT, Dean an o Director BERKELEY H. e. van norman, vice-director > >o dean University Farm schooi COLLEGE OF AGRICULTURE CIRCULAR No. 195 March, 1918 REVISED COMPATIBILITY CHART OF INSECTICIDES AND FUNGICIDES By GEO. P. GEAY STOMACH POISONS Acid Lead Arsenate Basic Lead Arsenate (Neutral) Paris Green Zinc Arsenite Tobacco Infusions Concentrated Tobacco Preparations FUNGICIDES Bordeaux Mixture Lime Sulfur Solution Sulfur Alkali Sulfides Cyanide Fumigation TRACHEAL POISONS KEY TO CHART: Data lacking: .Probably dangerous JDangerous combinations ^ ^ .Recommended combinations .., , .,. ..Probably safe Doubtful combinatious, m _ _ ^Doubtful useful under some conditions Paste on a Sheet of Cardboard and Hang up for Convenient Reference REVISED COMPATIBILITY CHART OF INSECTICIDES AND FUNGICIDES The present high cost of supplies and the scarcity of labor have brought the agriculturalist face to face with many new problems, not the least of which is that of pest control. With the exception of cyanide fumigation, the cost of an insecticide or fungicide is usually much less than the cost of its application. Spraying operations are often limited to a short space of time on account of unfavorable weather. The tendency to use, whenever possible, combination sprays in the control of two or more pests is thus accentuated. Untried com- binations are apt to be made use of, sometimes with disastrous results to fruit and foliage. The matter of the compatibility, or incompati- bility, of insecticides and fungicides, therefore, is now of unusual interest. In complex mixtures of this sort grave chemical or physical changes may take place which render the combination wholly unfit for use. On the other hand, the original ingredients may remain unchanged, or may be improved by their new associates. Numerous experiments have been made to determine the advisa- bility of various combination spraj^s and many of the results have been published in bulletins of the U. S. Department of Agriculture, the state experiment stations, and in agricultural journals. These reports are so scattered, and at times the conclusions of the various investigators are so conflicting, that one must spend much time in a search of the literature before arriving at a definite conclusion. In order to bring this information into more available form and to make it more easy of access, it was condensed into tabular form and pre- sented before the State Fruit Growers' Convention in assembly at Davis, June 1-6, 1914. It is believed that this compatibility table and its discussion was the first comprehensive one of its kind ever made public. It was therefore presented with no little hesitation, and was considered as a tentative one only. Some little publicity was later given the table through its publication in at least six agricultural publications. Discussion and criticism were invited so that if any of the classifications were incorrect, or did not correspond with practical experience, the faults could be corrected. Since then, the matter has been followed closely, and minor corrections have been made to cor- respond more closely to the best practice. The original table has been simplified and arranged in the form of a circular chart, 1 and is now believed to be an accurate reflection of the best thought of the various investigators who have worked on the subject of compatibility of in- secticides and fungicides. The accompanying revised chart is pub- lished in the hope that it will be of value in indicating the sprays which can be applied in combination, thus reducing the cost of ap- plication one-half, or in warning of dangers in apparently harmless mixtures. i The writer is indebted to Prof. C. A. Noren, Oregon Agricultural College, for suggesting the circular arrangement of the chart. A circular chart based upon the writer's original table and investigations by Mr. W. C. Morris, Hastings, New Zealand, has been published in the New Zealand Journal of Agriculture, vol. XII, no. 3, p. 193, and in the Fruit World of Australasia, vol. XVIII, no. 10, p. 17. The stomach poisons are arranged about the upper left segment of the circle, the fungicides about the upper right segment, and the tracheal poisons (contact insecticides, gaseous, liquid, and solid) about the lower segment. Lime-sulfur solution, sulfur, and the alkali sul- fides have important uses both as an insecticide and as a fungicide, consequently the segments upon which they are arranged are made to overlap, to indicate their double utility, and to avoid duplication and an unnecessary number of lines. The materials listed have been strictly confined to the standard remedies in common use in orchard spray practice. Colored connecting lines are made use of to indicate the effect of mixing. The color scheme of railroad signals has been adopted and is as follows : red, danger ; green, proceed ; yellow, pro- ceed with caution. The meaning of the solid red and green lines appears to need no further explanation. A yellow connecting line is used to indicate that mixing is apt to produce chemical or physical changes which destroy the original properties or value of one or both of the ingredients, or that the mixture is recommended for use in cer- tain sections, but not in others, or for certain specific purposes. The broken lines indicate combinations which have not been experimented with, or not sufficiently so to definitely establish their status. The probabilities are, however, indicated by the color scheme as nearly as can be judged. For the use of the chart in connection with materials, the names of which are not listed thereon, the following list of equivalents has been arranged: Names not Listed Coal-tar ' ' Dips ' ' Dilead Arsenate Dry Lime-sulfur Iron Sulfide Lead Hydrogen Arsenate Liver of Sulfur Miscible Oils "Neutral" Lead Arsenate Nicotine Sulfate Potassium Polysulflde Sodium Polysulflde "Soluble" Oils ' ' Standard ' ' Lead Arsenate Sulfide of Potash Sulfide of Soda Sulfur Pastes, Commercial (as now manufactured) Tobacco Extracts, Home-made Tobacco Juice or Tea ' ' Tri-plumbic ' ' Lead Arsenate Wettable Sulfurs, Commercial (as now manufactured) Wettable Sulfurs, home-made (con- taining glue, flour, or dextrin) Corresponding Compatibility Soap-oil Emulsions Acid Lead Arsenate Lime-sulfur Solution Sulfur Acid Lead Arsenate Alkali Sulfides Soap-oil Emulsions Basic Lead Arsenate Cone. Tobacco Preps. Alkali Sulfides Alkali Sulfides Soap-oil Emulsions Acid Lead Arsenate Alkali Sulfides Alkali Sulfides Sulfur Tobacco Infusions Tobacco Infusions Basic Lead Arsenate Sulfur Sulfur