THE PECAN ROSETTE PROBLEM

Pecan Research
--------- J. H. Burkett, Nut Specialist, State Dept. of Agriculture, Austin, Texas Rosette is in my judgment caused from impoverishment or lack of proper nutrition. The mere fact of its being found on different soil types does not mitigate against this theory. Different Kinds of Roots There are three kinds of roots common to all pecan trees. The large brace and tap root system radiating in all directions, similar to the top or spray formation. Then the fibrous roots which are much more numerous than the large brace roots and which extend in all directions from these brace and lateral roots. The last and least in size but of equal importance arising from the many fibrous roots are myriads of hair roots. The offices of each kind of these roots are to a certain extent separate and distinct and yet are to a large extent dependent one on the other. The large brace roots are usually located within one to four feet of the surface of the soil and serve the purpose of affording anchorage to the tree and bracing it against storms as well as furnishing an abundance of stationary capillaries. The fibrous roots serve the purpose of carrying the crude plant food to the larger roots, and the hair roots serve the purpose of reaching out after the plant food in the soil which is held in solution, and conveys it 60 FOURTH ANNUAL MEETING to the fibrous roots. The fibrous roots conveying it to the larger roots which in turn convey it to the stem or trunk of the tree where it is conveyed to the remotest parts of the tree. If, from any cause, the hair roots cannot extend outward rapidly enough to secure the requisite amount of crude plant food, either because of the soil being too dry, wet, coarse, loose, fine, or hard, then the tree is not properly nourished, and rosette and die-back are the result. Wherever and whenever these conditions exist we have rosette. If these conditions can be overcome by artificial means rosette can be curd. There seem also some other factors that contribute to the development of rosette. It is believed that certain pecan seed will produce trees that are more tolerant to the untoward soil conditions which super induce rosette and die-back than other seeds. It has been observed that where two pecan trees found growing in close proximity one may be affected with rosette and the other may be strong and vigorous. This can hardly be accounted for satisfactorily in any other way, except to attribute to the difference in the vitality of the seed that produced the trees. It has also been observed that where these conditions exist one tree may have a lateral surface root system and the other, the healthy tree, has a root system that extends downward. It is believed that this trait is also inherent in the seed from which the trees originated. If a tree or trees having originated from a variety of pecan that is inclined to develop right angled lateral root, happens to be brought under cultivation the root system being constantly disturbed by the plows, the trees will develop rosette and die-back. If on the other hand the varieties that develop a deep, penetrating root system be brought under cultivation the plows do not disturb the roots to the same extent because the roots lie below the reach of the plow. As before stated the roots of the pecan are divided into three classes, the hair roots, and fibrous roots and tie large woody roots; while the top has the stem and trunk, the branches and twigs, and the leaves. The roots, trunk, limb, and leaves are the prime essential organs of the tree. At the extremities of the roots are to be found the mouth parts whose office it is to take in the plant food from the soil and at the extreme ends of the branches are the leaves whose office it is to elaborate the crude plant food taken up by the hair roots and change it into plant food. In performing this office the leaves through the influence of the sun and air change the plant food elements taken up by the roots into sap and sends it downward to the branches, stems and roots in order that all may continue to grow and enlarge their usefulness one to the other. If the soil and moisture conditions happen to be unsuited to the needs of the hair root system, the tree develops rosette or die-back.

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