Peach Yellows, Little Peach and Peach Rosette 



M. B. Waite, Pathologist in Charge, Investigations of Diseases of Fruits, U.S. Department of Agriculture 



* 



THE "little peach" disease is import- 

 ant inasmuch is it occurs quite ser- 

 iously in Michigan, New York and 

 Ontario. This disease resembles yellows 

 in many respects, particularly in its foliage 

 symptoms, yet it is very distinct, in fact 

 the opposite in other respects, namely, its 

 fruit symptoms. The fruit on trees affect- 

 ed by "little peach" is undersized, belated 

 in ripening but similar in color and ap- 

 pearance to the normal fruit, especially to 

 imperfectly developed specimens. It is 

 rather flat and insipid but not so dis- 

 tinctly off-flavor as in the case of the yel- 

 lows. It may be only slightly reduced in 

 size in mild cases or in extreme cases 

 may be reduced to tiny peaches less than 

 three-quarters of an inch in diameter. 

 Trees affected by the little peach rarely 

 produce the wiry, bushy growth. When 

 forced to throw water sprouts by heavy 

 cutting back or winter killing, they do to 

 some extent make twig growth resemb- 

 ling yellows. 



Trees with the little peach usually roll 

 their leaves upward and droop the fo- 

 liage as yellows occasionally does. The 

 leaves begin to discolor on the inside of 

 the tree, especially on the main limbs 

 and the yellowing proceeds outwardly as 

 the season advances. "Little peach" is 

 quicker than yellows, killing the tree or- 

 dinarily in three years instead of four or 

 five years. The twigs die back from the 

 top in the same way. It apparently 

 spreads more rapidly in the orchards and 

 since it has not the premature red spotted 

 fruit its symptoms are more obscure and 

 more difficult to recognize. This makes 

 it rather harder to handle than the yel- 

 lows. The "little peach" occurs mainly 

 in Michigan, Western New York, and to 

 some extent in Ohio, Permsylvania and 

 New Jersey. 



PEACH ROSETTE 



The rosette which occurs in Georgia 

 and the neighboring state of South Caro- 

 lina and also to some extent in Missouri 

 and Arkansas, is still another disease of 

 the same type. It is only interesting to 

 Ontario growers for comparison. The 

 affected trees produce small, very short, 

 bushy growth like extreme cases of the 

 yellows, but they are so dense as to form 

 small rosettes or bunches of leaves on 

 the trees. The affected trees usually 

 throw their fruit while it is still small 

 and the trees, in fact, are usually dead 

 by the time the fruit should ripen. Occa- 

 sionally trees partially affected produce 

 small green, shrivelled and imperfectly 

 developed fruit, but it is not premature. 

 J On the healthy side of half diseased trees, 

 which only rarely occur, the fruit is nor- 



„*The flftli instAlmenf of Mr. Waite's aildresK on 



FiingouR DiHnaHCR of Ontario Orcliardf ." given at, the 



ieonvention of I he Ontario KniifOrowors' Assotualion. 



mal. The trees mostly die, root and 

 branch, before the season is over. This 

 rapid death of trees affected by rosette is 

 a distinct advantage to the orchardist as 

 the disease mostly eradicates itself. 



HOST PLANTS OF TELLOWS GROUP 



Peach yellows occurs mainly on the 

 peach but it also occurs on the Japanese 

 group of plums sufficiently to be of im- 

 portance as a plum disease. So far as 

 we know, other plums are not affected by 

 it. It also occurs on the nectarine (the 

 smooth form of the peach), and on the 

 almond and apricot, these latter being, 

 of course, only occasionally grown within 

 the range of this disease. 



but further investigation, particularly in 

 Japan, would be necessary to determine 

 this. 



TELLOWS ON NURSERY STOCK 



Unquestionably yellows can be budded 

 into nursery stock. This has been done 

 experimentally, notably by Smith. I have 

 done it myself in a number of cases. 

 Naturally well-marked specimens are se- 

 lected for this purpose. Nurserymen or- 

 dinarily would not bud from pronounced 

 cases of the yellows. On the other hand, 

 incompetent help may secure bud sticks 

 from diseased trees, but what is more 

 likely, buds may come out from incipient 

 of incubating cases which do not show 



Sprajing by Hand Power in the Esiez Penin<ala of Ontario 



Orchard of J. O. Duke, Ruthven, Ontario. This illustration shows an excellent way to mount a hand pump. 

 There is plenty of room for the operators to work. 



The "little peach" is known only on 

 the peach and Japanese group of plums. 

 It may possibly also attack some other 

 stone fruits. The Japanese plums are so 

 peach-like that they form ready hosts for 

 these diseases. The rosette occurs on 

 the peach and on the native Chicksaw 

 plum, and probably also on the Japanese 

 group of plums. 



Apparently peach yellows and peach 

 rosette are native American diseases. If 

 this is the case, they are doubtless dis- 

 eases of our native stone fruits just as 

 year blight is with some fruits. Rosette 

 is probably a disease of the wild Chick- 

 saw plum. "Little peach" may possibly 

 be a native American but I doubt it, since 

 it only recently appeared and the date of 

 its appearance some twenty years ago 

 corresponds with the introduction of the 

 Japanese plum into American horticul- 

 ture. My suspicion, therefore, is that it 

 was introduced with the Japanese plums, 



78 



the true symptoms at the time. Smith 

 transmitted the disease by budding from 

 the apparently healthy side of a diseased 

 tree. Unfortunately buds cut from yel- 

 lows trees slightly affected grow fairly 

 well in the nursery. 



This is not the case, however, when 

 pits are used from diseased trees. So 

 far, all attempts to grow trees from dis- 

 eased pits have failed. Recently I planted 

 I DO pits from trees well marked with 

 yellows, with premature red spotted fruit, 

 and loo pits from typical cases of "little 

 peach." None of these grew. Not a singf' 

 seed germinated. In all cases, so far as I 

 know, where pits from well-marked dis- 

 eased trees have been used, a similar 

 result has been obtained. If this could 

 be assumed to be always true, it would 

 remove one great possibility of reproduc- 

 ing disease. Unfortunately we do not 

 know what happens when pits are taken 

 from trees only slightly affected or from 



