590 ANNUAL REPORT OF THE Off. Doc. 



The old standard formula- for Bordeaux mixture is the 64-50 for 

 inula, that is using a 50-gallon barrel as the staudard, pounds of 

 blue stone (copper sulphate) 4 pounds of lime to 50 gallons of water. 

 Where the lime is of good grade and where the plants are not easily 

 injured, as with Irish potatoes, cantaloupes and grapes, this for- 

 mula is probably the best thai can be used. However, on apples 

 and pears while they are ordinarily uninjured by Bordeaux, there 

 has been a great deal of trouble with russeting. This russetiug is 

 probably compensated by an increased quantity of lime and by di 

 luting the preparation. 



Furthermore, so much of the lime is bad that it is really safer to 

 use a larger quantity than the standard formula calls for. The 

 5-5-50 formula is therefore a little safer than the 6-4-50 and has come 

 to be regarded as a standard for apple spraying. For pear-blight, 

 apple leaf blight, and for the smut on the apple fruit and the rust 

 on the pears, the 4-4-50 answers very well. In other words, the for- 

 mula is slightly diluted. 



Where the lime is at all questionable its amount should be in- 

 creased to make up for the deficiency in strength. On this account 

 many growers are using the 4-6-50 formula. 



On peaches and Japanese plums Bordeaux mixture during rainy 

 seasons injures the foliage, producing not only the "shot hole" effect, 

 but frequently defoliating the trees, even before the fruit has ma- 

 tured. It is risky to spray peach trees or Japanese plums, in foliage, 

 with any formula of copper or in fact with any fungicide which we 

 have yet been able to find, but if they must be sprayed and the or- 

 ( hardist is willing to take the risk, a Bordeaux containing a larg^ 

 excess of lime should be used. We regard the 3-9-50 formula as the 

 best formula for peaches. 



APPLE SCAB. 



This fungus disease is one of the most serious apple troubles in 

 Pennsylvania. A similar disease occurs in the pear, caused by a 

 closely related fungus and is controlled by the same treatment. 

 They may therefore be discussed together. 



The scab fungus is especially susceptible to weather conditions. 

 Moist, rainy or muggy weather during the spring months greatly 

 favors the disease, while dry, sunny weather retards its progress. 

 The scab fungus germinates in drops of rain or dew. The spores 

 are able to germinate and enter the tree only during certain favor- 

 able spells of weather. We term these periods of moist weather in- 

 fection periods, and it is a good thing for the fruit grower to recog 

 nize such spells of weather as periods of infection when the scab and 

 other fungi are able to germinate and enter the fruits. It is neces- 

 sary to have the fruits and foliage protected by the spray before 

 these infection periods. As a result, apple and pear scab are both 

 rather difficult diseases to control during a moist season. Spraying 

 must begin very early. The first treatment should be when the fruit 

 trees are in bud, when the cluster buds have opened out, but before 

 the blossoms have opened. Usually by beginning on the earlier 

 blooming varieties and having everything ready to strike promptly, 

 the orchard can be sprayed when in bud before the blossoms open. 



The second treatment should be made just as the last blossoms 

 are falling. Here again there may be a difference of two or three 



