Neglected orchards in areas of high humidity or poor air drainage are most troubled with Spanish moss and Ball moss. When large and excessive growths of Spanish moss develop in pecan trees, the shading effect to the leaves is detrimental to tree vigor, bearing and growth, [Figure 7].
Control.—The Spanish moss plant like the pecan tree requires sunlight for vigorous growth. A pecan tree kept in a vigorous state of growth produces dense foliage that effectively shades accumulations of Spanish moss and retards its growth.
Spanish moss is not a problem in pecan trees in orchards which are sprayed with fungicide for disease control. Both Spanish moss and Ball moss can be controlled by spraying pecan trees with 6 pounds of lead arsenate per 100 gallons of water[3]. Do not allow livestock to graze in orchards sprayed with lead arsenate.
COTTON ROOT ROT
Cotton root rot disease is caused by the fungus Phymatotrichum omnivorum (Shear) Dvgg., a soil-inhabiting pathogen that attacks a wide range of host plants including the pecan.
The roots of the pecan tree are invaded during the summer when growth of the fungus in the soil is most active. The infected roots are killed, disrupting the transportation of water to the leaves, [Figure 8]. Trees diseased by cotton root rot produce yellow foliage, and shedding of leaflets occurs during dry periods. Diseased trees usually die 1 to 3 years after becoming infected.
Figure 7. Spanish moss accumulation in pecan trees reduces vigor from excessive shading.
Figure 8. Cotton root infected with cotton root rot fungus. Note the splitting and general deterioration of the root.