lyo Journal of Agricultural Research [voi.ni.No.^ 



Neither is rosette to be confused with sun scald, or "winterkill," which 

 affects young trees especially and manifests itself in the death of the 

 cambium at the base of the trunk. The roots are usually uninjured and 

 healthy sprouts soon put out from the base. Again, frost injury may 

 kill back the tips in a manner somewhat analagous to the staghorn stage 

 of rosette, but here the foliage symptoms are lacking, and in rosette the 

 death of the branches is usually most prominent in late summer, a season 

 far removed from frost. 



Both the yellows and rosette of peach in a general way suggest pecan 

 rosette. However, though some symptoms may be common to all three 

 diseases, the complete clinical picture is distinct in each case. Some of 

 the most prominent symptoms of peach yellows consist in the produc- 

 tion of abnormally long, spindling branches in dense groups due to the 

 putting out of normally dormant and possibly adventitious buds. Yel- 

 lowing of the leaves always occurs at some time during the course of the 

 disease; but in spite of the name "yellows," the leaves are often abnor- 

 mally dark green in a case of recent attack. The pushing into growth 

 of normally dormant buds and also possibly of adventitious buds is 

 likewise characteristic of pecan rosette, but the axes are shortened rather 

 than elongated as in peach yellows. In this shortening of the axes of 

 growth the resemblance to peach rosette is seen. In the last-named 

 disease the twigs are so much shortened that the leaves as they develop 

 become clustered into a compact rosette. Peach trees affected with 

 rosette usually die during the first and never survive the second season, 

 and those suffering from yellows rarely survive more than five seasons, 

 but rosetted pecan trees have been known to live for 15 years. More- 

 over, no case is on record of a recovery from peach yellows or peach 

 rosette, while recovery from a moderate attack of pecan rosette is fre- 

 quent, and not rare, even for the later stages. Furthermore, from the 

 experiments outlined in this paper it appears that pecan rosette is not 

 transmissible either through the seed or by budding or grafting, while 

 the infectious nature of peach yellows and rosette is well established 

 through experimental bud transmission to healthy trees. 



A striking resemblance is to be observed between pecan rosette and 

 ordinary chlorosis of various trees. In moderate cases of the latter dis- 

 ease yellowing of the leaves occurs without notable change in form or 

 size, and the conspicuous dying back of the branches from the tip is 

 lacking, but all gradations occur between such cases and those where the 

 symptoms closely simulate rosette of pecans. 



The spike disease of pineapples' bears some general resemblance to 

 rosette of pecans both as to effect and apparent cause. The leaves of 

 affected pineapples become contracted at the base so as to form a spike- 

 like blade, and the color of the leaf also becomes modified. It is claimed 

 that cottonseed meal, sulphate of ammonia, kainit, muriate of potash, 



' Rolfs, P. H. Pineapple lertilizers. Fla. Ap. Exp. Sta. Bui. so, p. 97-99. "899. 



