The fungous diseases attacking the pecan have not been thoroughly investigated. They have not, however, become so numerous or common as to cause serious damage except in a few instances. The true fungous diseases are usually propagated and disseminated by means of spores, and the most effectual method of control usually consists in spraying with Bordeaux mixture or some other fungicide. For all fungous diseases of the pecan which may be controlled by spraying no substance will give better results than Bordeaux mixture, and directions for preparing it are given at the end of this chapter. Paris green, at the rate of four ounces to each fifty gallons of liquid, may be added to the mixture for the destruction of biting insects. For effectual work in spraying large trees, a platform should be erected on the wagon-bed to make it possible to reach the tops with the spray. PECAN LEAF BLIGHT (_Cercospora Halstedii_): This disease of pecan leaves causes them to turn brown, wither up and drop prematurely. At first, small brown spots are noted. These become larger, and at length the whole leaf is destroyed. When attacked by this disease the tree makes no progress. An examination of the discolored areas, under a microscope, shows the presence of tuft-like growths of spores upon short conidiophores. As they become matured the spores are scattered by the rain or wind and so the disease is spread. It probably lives over from one season to another on the diseased leaves. The most effective remedy is to spray thoroughly three times with Bordeaux mixture. The first application should be given just when the young leaves are expanding, followed by two others at intervals of two or three weeks. The fallen leaves should, if feasible, be gathered and burned. Pecan Scab (_Fusicladium effusum_): This disease attacks the fruit, leaves and twigs. The husks of the diseased nuts become covered with dark spots or specks. They become hardened and crack open in places. As a result of the attack, growth is stopped, the fruit does not fill out and mature, but drops prematurely or, in some cases, remains attached to the trees long after the leaves have fallen. Round, black spots form on the leaves when attacked by the fungous. These become dead and brown and in most cases the whole leaf is destroyed. When attacked, the trees are usually so badly injured that they make little progress. Not all varieties are subject to the disease in the same degree and some appear to be entirely exempt. [Illustration: _Photo by H. A. Gossard._ FIG. 36. Spraying Pecan Trees.] Those varieties which are not attacked should be given preference in propagating work. The disease may be further controlled by spraying with Bordeaux mixture, as directed under leaf-blight.