16 BULLETIjST 1038, U. S. DEPAETMEXT OF AGRICULTUKE. 



highly probable that pecan rosette belonged to the group of non- 

 transmissible chlorotic diseases caused by improper nutritive supply 

 or injurious physical conditions. The possibility of the presence of 

 some parasitic organism was not entirely precluded, but it was 

 thought highly probable that the ultimate cause would be found in 

 some lack of balance in nutritive supply, or possibly in some toxic 

 substance or substances in the soil. These conclusions were based 

 entirely uj)on the results of field experimentation. 



Miller (54) observ^ed that buds from rosetted trees worked upon 

 liealthy stock in most instances grew into normal trees, but that 

 when a tree was decidedly rosetted its buds would sometimes develop 

 the disease when worked upon healthy stock. He is of the opinion 

 that rosette is due to soil relations and observed that in dry seasons 

 the disease is more prevalent. Eosette and a proper amount of 

 moisture, he says, do not go together. Impoverished soil, lack of 

 humus, overstimulation of growth, and use of improper fertilizers 

 all favor rosette. He states that the severest cases are incurable or 

 at least not curable by practical means. 



Fawcett (33) refers to pecan rosette in a short paragraph, and 

 Crittenden (26, pp. 44-45) briefly summarizes the work of Orton 

 and Eand. 



Matz (51. pp. 139-141) in a bulletin relating to various pecan dis- 

 eases and insects devotes a short section to rosette. He states that 

 the disease apparently occurs on all types of soil and at all seasons, 

 but that wherever it occurs it is most abundant during late summer. 

 He also says that rosette is more abundant on higher and more ex- 

 posed soils than in low and more protected situations. After 

 briefly describing the signs of the disease he adds that many of the 

 dead leaves adhere to the branches throughout the winter unless 

 blown off by strong winds. The disease is favored by planting in 

 open, sandy soil or where a hardpan exists near the surface. 



McMurran (50) in a paper dealing with field experiments and 

 observations states that rosette is generally considered to be the most 

 serious pecan disease. It is found upon a wide range of soil types 

 and under various conditions of culture and fertilization; but one 

 factor, he says, appears to run through it all. On the river flood 

 plains of Southern Louisiana the disease is practically unloiown. 

 Here the soil is deep and black and of high fertility and presumably 

 of high water-holding capacity as compared with the typical sand, 

 gand-clay, and clay soils of the Atlantic and Gulf Coastal Plains 

 where the disease is so prevalent. In Georgia and Florida probably 

 90 per cent of the affected trees are on hilltops and slopes. AU 

 cases on the bottoms that have been examined were found to be in 

 deep sand or in a clay or sand-clay soil underlain at 2 or 3 feet by 

 sand. It was noted further that large healthy trees 5 to 10 years old 



