June 1919 ^ 



Field Testing Copper-Spray, Etc. 



Continued from page 9. 



be determined only from investigations 

 covering a period of years. The best 

 spray practice should aim at keeping 

 the spray coaling always above the 

 maximum limit, and ordinarily good 

 practice should never take the risk of 

 falling below the minimum limit. 



Field Trials 

 During the two seasons that this 

 method has been in use, something like 

 75 schedules have been tested by the 

 writers. The following results are se- 

 lected as being representative. 



Apple Leaves at Crozet, Virginia 



Winesap apple leaves were tested at 

 Crozet, Virginia, June 23 to July 22, 

 1917. The orchard was about five acres 

 in extent and was sprayed with 3-4-.50 

 Bordeaux mixture on the date of the 

 first collection. Each sample was di- 

 vided, one portion being sent to the 

 Bureau of Chemistry, United States 

 Department of Agriculture, for exact 

 analysis, and the other tested by the 

 field method outlined above. The 

 analytical data is based on the dry 

 weight of the samples, and the field 

 tests data have been converted to the 

 same basis by assuming a constant 

 value of 35 per cent for the dry weight 

 of the leaves. A scale for equivalent 

 readings in milligrams of copper per 

 100 grams fresh weight of leaves is also 

 indicated in the figure. 



At this early period in the work the 

 samples were too small to give the best 

 results for so large a planting. How- 

 ever, there is reasonably close agree- 

 ment between the graphs secured by the 

 two methods, with the exception of a 

 few of the first determinations. 



Tests were made during July and 

 August, 1917, in two apple orchards, 

 A and B, at Crozet, Virginia, sprayed by 

 the owners with 3-4-50 Bordeaux mix- 

 ture according to their usual practices. 

 Both orchards had received a first 

 application of the mixture about the 

 middle of June. The readings indicate 

 the milligrams of copper per 100 grams 

 fresh weight of leaves. Two other 

 orchards, C and D, in the same locality, 

 bore light crops of fruit and for this 

 reason were given rather light spray- 

 ing of 3-4-50 Bordeaux mixture by their 

 owners. 



Tests before and after the secona and 

 third spray applications in these or- 

 chards gave the results shown in 

 Table I. 



Bearing Grapefruit Trees at Winter 

 Park, Florida 



Two spray applications on a commer- 

 cial basis were made on plats of bear- 

 ing grapefruit trees at Winter Park, 

 Florida, the first on March 9 and Ihe 

 second on April 16, 1918, using a power 

 sprayer devcloiiing ai)proximately 225 

 pounds pressure. The plats contained 

 30 trees each. Single samples of 200 

 grams fresh weight were taken from 

 each plat at intervals of about four 

 days until June 1. In this test 3-4-50 

 Bordeaux mixture was used with and 

 without a certain oil emulsion, and the 

 Burgundy mixture was also made up 



BETTER FRUIT 



with 3 pounds of bluestone. The tests 

 show consistent decreases in copper 

 content of the coatings. 



Citrus Nursery Stock at Bradentown, 

 Florida 



At Bradentown, Florida, comparative 

 tests were made with three strengths of 

 Bordeaux mixture, made up according 

 to 3-4-50, 2-2%-50, and l-l%-50 formu- 

 las. The applications were made in 

 February and March, 1918, on two 

 nursery plantings of overgrown sour- 

 orange stock. In Nursery I the trees 

 were about 6 feet high; in Nursery II 

 about 3 feet. A bucket spray pump was 

 used, and in each nursery measured 

 amounts of spray were applied to equal 

 lengths of the nursery rows to secure a 

 distribution of the spray as equal as 

 possible. The fresh weight of each leaf 

 sample approximated 100 grams. 



Page 21 



In every case the grower claimed that 

 6 pounds of bluestone were used in 50 

 gallons of the Bordeaux mixture. 

 Knapsack sprayers were used. With 

 the exception of field D one or more 

 applications had been made before test- 

 ing began. When samples could not be 

 taken immediately before and after a 

 spray application, estimates have been 

 made from the previous or subsequent 

 direction of the graph to determine the 

 probable values. 



The owner of field A, besides guess- 

 ing at the quantities of ingredients, 

 followed a faulty method of mixing the 

 spray. In spite of frequent applica- 

 tions, the results were very unsatisfac- 

 tory. If it is assumed that adequate pro- 

 tection from some specific celery disease 

 is secured by spray residues testing be- 

 tween 35 as a minimum and 45 as a 

 maximum for a transition zone, it will 



-easy! 



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San Francisco 



Ghirardelli 's 



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