286 



THE AGRICULTURAL NEWS. 



Septembee 4, 1909. 



BORDEAUX MIXTURE FOR SPRAYING. 



At the Ao;ricultural Ex]ieriinent .Station of tlie 

 University of Illinois, an exhaustive enquiry into the 

 properties of Bordeaux mixture has been carried 

 out. The results of this are published in Bulletin 

 No. 135 of that Station, issued in May 1909, and the 

 chief conclusions that are reached are given below. 

 They are interesting apart from their connexion with 

 the use of this fungicide for spraying alone: — 



1. Injury to foliage of trees following applications of 

 Bordeaux mixture is of common occurrence. Much of the 

 injury reported or observed 'is preventable. The principal 

 sources of injury as determined by obiservations are : — 



(a) Use of impure or improper materials. 



{/>) Carelessness in making the nnxture. 



((■) Improper and ineft'ectivc application. 



Bat when all precautions h?.ve been taken, injury .some- 

 times results. These non-preventable injuries are associated 

 Avith unfortunate weather c'oaditions, and particularly with 

 the action of rain and dew. 



2. The chemical changes occurring in making Bordeaux 

 mixture are still involved in some obscurity. That the 

 copper is deposited in the form of copper hydroxide, as has 

 been generally accepted, is denied by Professor Pickering, 

 Director of the Woburn Experiment Station. 



3. The adhesiveness of Bordeaux mixture depends very 

 anuch upon the manner of making', and upon the character 

 of, the lime used. With lime of good ipiality, a close approxi- 

 mation of equal parts of copper sulphate and lime gives 

 greatest adhesiveness. 



4. No definite experiments regarding the accumulation 

 of copper in the soil under sprayed trees have been conducted, 

 but from results reported of experiments by others it does 

 not appear that there is danger from this source. 



5. Leaf injuries are common and most .serious in neg- 

 lected orchards. Much of the injury following spraying is 

 attributable to abrasions of the epidermis made by insects, 

 and to infection by fungi preceding spraying. 



fi. The ideal spray compound that is peifectly effective 

 and at the same time perfectly harmless on all occasions and 

 under all conditions has not yet been discovered. Bordeaux 

 mixture most nearly approximates to the ideal, but its harm- 

 le.ssness can not be absolutely' de]iended ujion. 



7. Injuries to foliage do sometimes follow ajiplications 

 of ];ordeaux nnxture and appear to be unavoidable. The 

 carbon dioxide contained in the air and in rain-water is 

 accepted as an activ? agent in rendering soluble the copper 

 of ISordeaux mixture, and it is believed that the ammonium 

 <;ompounds brought down by rain may also exert a solvent 

 notion on the copper. 



8. Laboratory exiieriments gave results showing that 

 the copper of Bordeaux mixture remained insoluble for long 

 periods. Field experiments, however, directly contradict 

 the laboratory results and show conclusively that, under 

 ^>rchard conditions, copiper, in small (piantity, becomes 

 .sfiluble very soon after deposition, and continues to appear 

 us long as any of the mixture remains upon llu' leaves. 

 The presence of lime in exce.ss does not prevent solution of 

 the copper. 



9. No evidence has been obtained in support of the 

 ^suggestions of authors that solution of copper occurs through 

 the agency of gernnnating spores, or through secretions 

 from leaf surfaces. 



10. Actual demonstration of llie presence of copper in 

 dead leaf cells has not been made, but the theory of penetra- 

 tion, and of death of cell protoplasm, by dir.ct contact with 



copper is regarded' as more jirobable than the theory of 

 transnussion of toxic effect without penetration, as advanced 

 by Bumm. 



11. The value of Bordeaux mixture as a fungicide depends 

 upon the contained copper. The action is preventive and not 

 curative. 



12. Spores of different fungi resist the action of copper 

 in varying degrees. 



13. The experiments made do not establish any direct 

 and positive connexion between spraying with well-made 

 Bordeaux mixture and yellowing of leaves, but do show that 

 improperly made mfxtures may- cause yellov.'ing, and that 

 yellowing results from use of simple solutions of copper 

 sulphate. 



14. Healthy bark of apple trees is impermeable to 

 Bordeaux mixture and solutions of cojiper .sulphate. Copper 

 sulphate solutions are absorbed through 'wounds and promptly 

 kill the leaves, which then become brown. 



1.5. The importance of rain and dew as agents causing, 

 brown-spotting of foliage following applications of Bordeaux 

 mixture is well attested by the uniform results obtained from 

 experiments with covered and uncovered trees. 



16. Milk of lime does not cause brown spots even wdien 

 applied in large cpiantity, but burning quickly follows appli- 

 cations of copper sulphate solutions even wdien the solutions 

 are very dilute. It is therefore concluded that copper iii 

 solution is the active agent resjjonsible for the burning of 

 foliage. 



17. From comparisons between leaves sprayed witli 

 Bordeaux mixture and milk of lime, with Bordeaux mixture 

 only, with milk of lime only, and leaves that had not been 

 sprayed, it was found that all leaves on -which lime had been 

 used were distinctly larger than those receiving no milk of 

 lime. This suggests a stimulating action on the part of the 

 lime — whether by direct action on the leaves or by reason of 

 the protective covering aUbrded has not been determined. 



18. Bordeaux mixture has a decided influence upon the 

 colour of leaves. Leaves coated with lime become in some 

 degree darker in colour than untreated leaves, but the .shade 

 is not .so deep as is assumed unc'tr a coating of Bordeaux 

 mixture. 



19. There appears to be no correlation between the 

 character of a stQjrm and :he rate of the solubility' or the 

 amount of copper found in solution in the waters collected 

 from sprayed trees. Neither is there any evidtnce that 

 electrical storms increase the amounts of copper in .solution. 



THE OBJECTS OF SCHOOL GARDENING. 



A circular for teachers, containing information ia 

 connexion with school gardens, has been recently issued 

 by the Superintendent of School Gardens in Ceylon. 

 This inforniatioii includes particidars of the objects of 

 school gardens, which are given below as they should 

 be of general interest : — 



(1) To brighten the surroundings of the school, and 

 make it what it ought to be, namely, a pleasant resort for the 

 boys and not a bare and unattractive building. 



(2) To lighten the routine of class work by varying it 

 with outdoor work of a recreative nature. 



(3) To exem[)lify order, form, neatness and good tast« 

 in the laying out of the premi.ses. 



(4) To furnish a field for nature study, i.e., the .study 

 of natural objects in their natural surroundings. 



(5) To serve as object-lessons in horticulture, i e., the 

 cultivation of useful and ornamental plants. 



