Nov. i6, 1914I Pecan Rosette 1 73 



very often completely recover. However, with well-advanced cases, 

 especially where dying back of the branches is prominent, there is so little 

 chance for recovery that it would seem better to replant with sound, 

 healthy, new trees, notwithstanding the fact that the unfavorable soil 

 conditions may persist and cause a second failure. 



As to the advisability of using rosetted nursery stock, no absolute 

 statements can be made with the present state of knowledge concerning 

 the cause of the disease and varying resistance of the stock to that cause. 

 However, orchard and nursery records show rather clearly that a differ- 

 ence in resistance of stock does exist. This being granted, it is reasonable 

 to suppose that among nonrosetted and rosetted stocks in the same nur- 

 sery the latter, if ultimately set out in soils tending to cause rosette, will 

 be far more likely to give rosetted orchard trees than the former. This 

 theory is borne out by the fact that in one large orchard where records 

 of the condition of the nursery stock used in planting were kept, observa- 

 tions after several years showed a much higher percentage of rosetted 

 trees from the rosetted stock than from the nonrosetted stock. It is true 

 that the rosetted stocks were set together in one part of the orchard and 

 that some difference in soil constituents not revealed by soil borings may 

 have caused the difference in prevalence of the disease, but this seems 

 hardly probable. 



Hitherto, pecan nurserymen have paid little attention to the presence 

 of rosette in the nursery stock used in budding and grafting except in 

 extreme cases of the disease, and it is thought by the authors entirely 

 possible that part of the wide prevalence of the disease may be due to the 

 dissemination of susceptible stock from the nurseries. The disease is a 

 serious one on account of the fact that crop production and recovery from 

 well-advanced stages are seldom seen, and for the good of the pecan 

 industry in general the number of cases of rosette should be kept at a 

 minimum. In view of these facts, the discarding of all rosetted nursery 

 stock is to be strongly recommended. 



SUMMARY 



Pecan rosette has been rather generally recognized by growers as a 

 serious disease almost from the inception of pecan orcharding. It does 

 not appear to be limited to any particular soil type, topography, or 

 season. The disease first makes itself evident through the putting out 

 of undersized, more or less crinkled, and yellow-mottled leaves. The 

 veins tend to stand out prominently, giving a roughened appearance to 

 the leaf blade, and the lighter areas between the veins are usually not 

 fully developed. The axes of growth are usually shortened, so that the 

 leaves are clustered together into a sort of rosette. In well-marked cases 

 the branches usually die back from the tip, and other shoots are developed 

 from normal or adventitious buds, only in their turn to pass through the 

 same series of symptoms. 



The nonparasitism of the disease seems rather definitely established 

 experimentally from the nontransmission by seed, the negative results 



