GEAPE-SPRAYING EXPERIMENTS IN MICHIGAN IN 1909. 



Counts Avere made (tf tlie total number of berries on 1,000 average 

 bunches in the vineyard and of the rotten berries on 1,000 average 

 bunches in each phit. The percentage of rot was computed from these 

 data. It has been noticed that in grapes trained on the Kniffen system 

 the fruit on the lower wire seems more susceptible to rot than that 

 above. In order to get more accurate data on this subject counts 

 were made in the check on the two wires separately. The following 

 table shows the percentage of rot on the dili'erent plats: 



Table II. — Results of si>ruying experiments on nine plats of Concortl grapes in 

 Mr. (liddiniis's rAneyard, near f.airlon. Mich., 1909. 



Fungicldfi used. 



Amount 

 of rot. 



4-4-.50 Bordeaux mixture 



4-3-o0 Bordeaux mixture 



4-.3-.'J0 JJordeaux mixture, with 2 pounds of iron sulphate 



4-2-.")0 Bordeaux mixture 



Check, unspraj'ed , ujijier wire, 34.3 per cent; check, unsprayed, lower wire, 45.4 



per cent 



3-2-.50 Bordeaux mixture 



Ammoniacal copper carbonate 



Neutral copper acetate 



Self-boiled lime-suli)hur 



Commerciallime-sulphur...; ' 



Per cent.. 



0.10 



.10 



.10 

 10 



.•?9.85 

 .03 



2.60 

 .48 



•2. 30 

 .84 



Xeutral cof)per acetate was used in the fifth spraying on plats '.> 

 and 10, the others being sprayed as before. 



There was a heavy snowstorm accompanied by a freeze before all 

 the grapes were picked, and a considerable quantity of the fruit on 

 all the plats but the check was frozen. It is therefore impossible to 

 compare the yields of the- different plats. This, however, is unimpor- 

 tant, as it has been found that individual vines vary greatly in their 

 productiveness and the most accurate method of determining the 

 amount of rot is by counting. The contrast between the condition of 

 the fruit in the check and the sprayed plats was quite striking, and 

 there was a marked difference between the amount of rot on the 

 upper and lower wires of the check. It is possible that a system of 

 high-arm pinning might be practiced which would give better ven- 

 tilation under the vines and allow them to dry off more quickly. 

 However, more observations are needed on this point. 



The grapes in the check were so badly injured by rot that it was 

 impractical)l(' to attempt to market them except in bulk, the cost of 

 the labor required in separating the few good bunches from the 

 rotten fruit being more than the difference in price between wine 

 and table giajK'S. On the other hand the rot in the plats sprayed 

 with the different strengths of Bordeaux mixture was practically 



[Cir. 6.5] 



