64 



6. Finally, there is the application of fungicides, such as Bordeaux mixture, 

 Eau Celeste, and Ammonio-carbonate of copper. None of these have yet been 

 shown to be effective against curl, but I am of opinion that none of them 

 have yet been tried with sufficient care. The ordinary formulae given for 

 these mixtures are too strong for the peach, being found to kill the foliage. 

 If they are tried, they should be used at half strength or even weaker, 

 unless they be applied in the winter, when the full strength will do no harm. 

 I would advise anyone experimenting in this line to rely upon winter treat- 

 ment, and treatment at the time when the leaves begin to appear. It does 

 not seem to me likely that later treatments will do much good, unless, 

 indeed, they diminish the force of the disease so as to lessen the damage 

 the following season. The action of these fungicides is much less marked 

 in a wet season, because they are washed off by the rain ; in any case where 

 a spraying is followed immediately by rain, little good can result unless the 

 spraying be repeated as soon as the rain has dried off. A winter spray of 

 sulphate of iron may be found useful, using one to two ounces of the crystals 

 dissolved in a gallon of water. These treatments are of doubtful value, as 

 far as curl is concerned, and were it not that they are useful in other ways 

 I would not mention them. 



Curl should not be confounded with peach-aphis. Seen at a distance the 

 effect of the aphis is similar to that of curl, but on close examination the 

 difference is apparent at once. In the case of curl, pure and simple, no 

 insects of any kind will be found, while in examining peach leaves attacked 

 by aphis the distorted leaves will be found swarming with small green and 

 brown insects. The two diseases may, however, occur together ; but even 

 then there is little difficulty in distinguishing the distortions of curl from 

 those caused by aphides, as those of the latter lack the livid thickening and 

 bulging so characteristic of curl. The treatment for peach-aphis is entirely 

 different from that recommended for curl." 



This closes the quotation from my original article, and I wish to call 

 especial attention to the second sentence in the sixth section of it : 



"None of these (copper compounds) have yet been shown to be 

 effective against curl, but I am of opinion that none of them have 

 yet been tried with sufficient care." 



When I wrote thus, I did not know that several years earlier curl 

 had been successfully treated in California with fungicides. Such, 

 however, was the case, and from this beginning a method of treatment 

 has been worked out which applies well to the conditions in this State, 

 and which is a most profitable one in those regions where the losses 

 from the disease are large and constant. The main points in the 

 treatment are winter spraying, or rather early-spring spraying, with 

 full-strength Bordeaux mixture, and care in the application of the 

 spray. Fully approving them, from observations made on the disease 

 in this State, I give here the main conclusions arrived at by Professor 

 Pierce : 



SUMMARY. 



(1.) Peach leaf-curl has a world-wide distribution, occurring in every 

 region in which the peach is grown. In humid localities it is a leading 

 hindrance to peach culture, and in portions of the Pacific coast States it has 

 greatly limited the extent of the industry. 



