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Bulletin 147 May, 1918 U IVERSITY OF FLORIDA Agricultural Experiment Station DISEASES AD I SECT PESTS OF THE PECA By J. MATZ FIG. 45.-Pecan nuts affected with mildew Bulletins will be sent free upon application to Experiment Station, GAINESVILLE, FLORIDA CONTENTS Page INTRODUCTION :.................... 135 PART I.-DISEASES INJURIOUS TO THE PECAN 135 Diseases of Foliage and Nuts- Scab 135 Anthracnose 137 Mildew 138 Dise~ses Primarily Affecting the Wood- Pecan Rosette 139 Dieback I ••.•••.•••.••••.••.•••••••••• ••·••·••••··••·•••• 141 Diseases Affecting the 'Nuts only- Pink Mold 144 Kernel Spot 144 Diseases Affecting Foliage only- Brown Leaf Spot ...............•........................ 145 Nursery Blight 146 Leaf Blotch 146 Minor Troubles- Winter Kill 147 Salamanders ...................•........................ 148 Mistletoe 149 PART II.-INSECTS INJURIOUS TO THE PECAN , 150 Pecan Leaf' Case-.Bearer 150 Pecan Nut Case-Bearer :: 152 Pecan Shuckworm 153 Pecan Cigar Case-Bearer · .. ···················· 154 Fall We'~worm 155 Walnut Caterpillar 155 Pecan Bud-Moth 157 Flat-Headed Apple-Tree Borer 157 Hickory Twig-Girdler 159 Shot-Hole Borer 160 Oak or Hickory Cossid 160 Hickory Phylloxera 161 DISEASES AND INSECT PESTS OF THE PECAN By J. MATZ A number of diseases and insect pests attack the pecan more or less seriously. In order to combat them successfully it is necessary to know their characteristics, to recognize their dif­ ferent stages, and to understand the different methods by which they develop. By recognizing a disease or insect pest in its in­ cipient stage, a great saving in the year's crop of nuts may be made and a more likely check be set against the spread of the disease or insect pest. It often happens that diseases of plants caused by parasitic, plant-like organisms (fungi) and injuries caused by insects are mistaken for one another under the popu­ lar but erroneous term, "bugs." Upon close examination one can distinguish the mechanical and often clean-cut injuries that are caused by biting and boring insects from the diseases that are caused by fungi. The latter seldom result in an actual cutting out of the affected parts. Discoloration, wilting, and a breaking up of the plant substance, and the ultimate dropping or dying of the affected parts, are the main characteristics of fungus attacks. Jt is essential that these two types of injury as well as the dif­ ferent diseases and insect pests be recognized if the correct means of control are to be applied. This bulletin describes the most common pecan troubles and offers methods by which they ean be controlled. Credit for a part of the information in this bulletin is here given to publications of the Bureau of Plant Industry, U. S. D. A., and especially to John B. Gill, Bureau of Entomology, for the use of data on insects and for some illustrations. PART I.-DISEASES INJURIOUS TO THE PECAN SCAB Fusicladiurn effusum Wint. Scab affEcts the leaves, twigs and nuts cf the pecan tree, with the result that the leaves are distorted and occasionally are shed, the young twigs are injured and sometimes killed, and the crop is reduced by many of the young nuts dropping before maturity. The fungus which causes scab is evidenced by a dark green, smoky, superfkial growth which is usually confined to rounded spots. 135 136 Florida Agricult'uml Expe1'iment Station I On t~e ~eay~s ~fi.9s. A6 ~n4 4;7_), t~e spots;/are ~li~~~lr> ~ais~d and vary m Size from sman black specks to one-fourth mch m diameter. Both surfaces of the leaves may become infected, in which case the dark, velvety growth constituting the spore-bear­ ing part of the scab fungus is seen on one side of the spot only, the opposite side being hard, more or less smooth, and black. On the nuts, the first appearance of scab is similar to that on the leaves, except that owing to the fleshy nature of the green outer covering of young nuts the affected areas appear at first more or less sunken in the green :.1.nd soft tissue. Under conditions favorable for the development of the disease the whole surface of the green nut may· become covered wit h the black, fungus growth (fig. ' 48) , arresting development and preventing maturity of the kernel. Frequently, the fungus incrustation causes FIG. 46.-P e can ·.. scab on upper the Iayer 0 f tissue With which surface of leaf it is in contact to break (fig. 49), thus forming an entrance for other molds, and a general decay follows. On the twigs, par­ ticularly the younger ones, the spots are smaller than on either the leaves or nuts and consist of a flat, black, round center of f~mgus growth in a concave depression in the bark. Affected twigs become stunted and are more or .less shrunken. (Fig. 50.) This resultant condition in the nut-bearing stems often causes the im­ mature nuts to drop. The presence of scab fun­ gus on the twigs is a likely source for carrying the infection from one growing season to another. FIG. 47.-P e can CONTROL.-Fallen leaves and husks from scab on lower surface of leaf scabby trees should be removed in the fall and winter and be destroyed. At least one applica- tion of a standard fungicidal spray, such as lime-sulphur solu­ tion or bordeaux mixture, should be m:;tde late in the fall or win­ ter to destroy the fungus spores which may be present in great abundance on the tree, and particularly on the younger twigs. Bulletin lJ,,7, Pecan Diseases and Insects 137 Dust, consisting of a mixture of 90 parts finely ground sulphur and 10 parts powdered arsenate of lead, may be applied with a dusting machine to the tree as soon as the buds open. The practicability of spraying FIG. 48.-Pecan s cab 0 n large pecan trees with liquid sprays nearly mature nut may be determined chiefly by the de- gree of susceptibility of the particu­ lar variety to scab, and by atmos­ pheric and climatic conditions. In some localities one or two applica­ tions of bordeaux mixture will insure FIG. 49.-Pecan scab on a check to the disease, while in others young nnt. Note the several applications of the same fun­ cracked hull gicide at intervals of two weeks may not give any appreciable results. There is a marked difference among pecan varieties in their susceptibility to scab. Many selected and budded standard varieties are less susceptible than unselected seedling trees. ANTHRACNOSE Glomerella cingulata (Stonem.) S. & V. Anthracnose affects the leaves and nut of the pecan. On the leaves it produces somewhat large, light brown to reddish, irreguI.u' blotches often covering a greater part of the leaf, and eventually causing the leaves to fall. At this stage the spores of the fungus are de­ veloped in large numbers. These are carried over the winter in the dead leaves and are dis­ seminated the following spring, causing, uncleI' conditions of high temperature and humidity~ fresh outbreaks on the leaves and nuts. On the nuts (Eg. 51) the blotches are irregular, black and slightly sunken in the surrounding green tissue of the hull. With the advance of the disease, the whole surface of the nut rna;).. become affected and the pink masses of spores FIG. 50.-Pecan scab on young are produced in large numbers. Under condi­ twig tions favorable to the development of the dis- 138 Flo1'ida Ag1'icultU'ral Expe1'iment Station ease, and especially when a severe attack occurs early in the growing season, dropping of immature nuts may result, These nuts, like the leaves, serve to carryover the disease from one season to another, The anthracnose fungus is sometimes present in the weakened tissues of twigs, but there is no record of its causing initial in- . FIG. 51.-Pecan nuts affected with anthracnose (Jour. Agl. Res., Vol. 1, No.4.) jury to the woody parts of the pecan tree. The attacks of this fungus are not restricted to the pecan alone. Recent investiga­ tions have shown it to be identical with the fungus which causes the well known and destructive "bitter-rot" disease of the apple. CONTROL.-Since the anthracnose fungus reaches greatest de­ velopment and produces spores more frequently and more abun­ dantly on fallen and diseased leaves and fruits, it is essential as a preventive measure that all dead and infected leaves, hulls, and nuts be removed and destroyed. This should be followed in the winter with a dormant spray, using a strong bordeaux-mixture solution. Another spray should be given soon after the buds open, and if necessary, two or three sprays be given in the earlier part of the growing season. The disease should be checked before the rainy season begins. MILDEW Microsphaera alni Wallr. Pecan mildew is recognized by the superficial, flour-like, whitish coating which. sometimes covers whole leaves and nuts, Bulletin 147, Pecan Diseases and Insects 139 (Fig. 45.) It may be first observed as small flakes on the leaves and nuts. Later the disease spreads all over the surfaces of the attacked parts and ultimately causes a yellowing and dropping cf the leaves. The greatest damage, however, is to the young nuts. Under humid conditions an excessive dropping of imma­ ture nuts may result. The disease usually starts from the lower and more or less shaded branches, spreading gradually upward. The causal fungus is disseminated during the summer by wind or other carriers, from minutely short and erect fungus branches which produce at their tips minute spores, in easily detached chains. Toward the end of the growing season, or at a time when conditions of humidity and temperature are less conducive to fungus growth, the white coating becomes less evident, and minute, black and more or less hard and resistant spore cases are produced.

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