THE GRAPE BLACK-ROT AND ITS CONTROL 



^y Prof. Lorenz Greene, Iowa State College, Horticultural Department 



Most grape-growers in the vicinity of Council Bluffs and other local- 

 ities in the Missouri valley are considering the question of whether or ' 

 not they shall spray their grapes this year. Many of them have already 

 purchased materials and machinery for this purpose. Some growers 

 have not as yet been troubled with the rot and are loth to go to the ex- 

 pense of spraying until there is more evidence for the necessity. If 

 they are located at some distance from infested vineyards, they will 

 probably not be troubled for a season or two. But it must be remem- 

 bered that many of the growers who have suffered severe losses the last 

 year were not troubled prior to two years ago, and many had never seen 

 the rot in their vineyards before. The rot can be kept under control 

 much easier if taken in hand early than if allowed to gain a strong foot- 

 hold in the vineyard it requires two years' spraying before the most 

 • profitable results can be secured. 



Therefore, it seems that the better method will be for the extensive 

 grower to spray his vineyard whether he has been troubled with rot or 

 not. 



Several mixtures have been recommended for use in black-rot con- 

 trol, but Bordeaux mixture is at present the one most universally used. 

 The United States government and one or two of the state experiment 

 stations recommended the use of five pounds of copper sulphate and five 

 pounds of lime to fifty gallons of water. Weaker solutions have been 

 found good, but until further evidence of their efficiency is secured it 

 will be best to use this formula. 



Lime sulphur, both commercially and liome prepared, have excellent 

 results. The self-boiled mixtures are also used. If the commercial 

 brands are used after the dormant season they should not be used in 

 stronger solutions than one part of the mixture to fifty parts water, as 

 even this solution burned the foliage in some of the government work 

 last year. Weaker solutions will be tried by different experimenters this 

 year. 



In applying these mixtures there will be a tendency on the part of 

 the growers to feel that they can control the rot by driving the sprayer 

 on only one side of the row. The machine should pass both sides of 

 every row. If the opposite side of the vine is examined after the 

 sprayer passes, it will be found that it has not been thoroughly covered. 

 These unprotected places will serve as a propagating-bed for the disease, 

 which will spread to other parts of the vine. Thoroughness will be the 

 safeguard. 



