Part 4

Pink mold, Cephalothecium roseum Corda, usually occurs on nuts infected with the scab fungus. The pink mold fungus apparently enters the nuts through scab lesions on the shucks and continues to produce masses of pink spores on shuck surfaces until late fall. The fungus sometimes invades the kernel of thin-shelled pecan varieties causing “pink rot” which is characterized by an oily appearance of the nut shell and a rancid odor.

Control.—Pink mold rarely occurs on the shucks of nuts in the absence of scab disease. In areas where scab disease control is regularly practiced pink mold is not a problem.

SPANISH AND BALL MOSS

Spanish moss, Tillandsia usneoides, and Ball moss, Tillandsia recurvata L., are not parasitic to the pecan tree and are similar to lichens in that they both derive their food from the air, rain or atmospheric moisture.

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. 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.

Control.—An effective control for cotton root rot disease has not been developed.

New orchards should not be planted in soil having a history of cotton root rot disease.

Pecan Insects and Their Control

PECAN NUT CASEBEARER

The pecan nut casebearer, Acrobasis caryae Grote, is the major pest of pecans in Texas. Early in the spring, the overwintered generation feeds first in the buds and then in the developing shoots, causing them to wilt and die. Succeeding generations feed on the nuts during the late spring and summer, Figure 9. Severe infestations may destroy the entire crop of pecans.

The adult is a light gray moth which is about one third inch in length. The wings are gray, and the forewings have a ridge of dark scales across them about one-third the distance from the base. The moths fly at night and spend the day in concealment.

The young larvae are white to pink, but later become olive gray to green and attain a length of about one-half inch.

This insect passes the winter as a partially grown larva in a tiny silken cocoon called a hibernaculum, which is usually attached to a bud, Figure 10. In the spring, the larvae feed for a short time on the buds, after which they tunnel in the developing shoots until they reach maturity, Figure 11. Pupation usually occurs in these burrows, and the moths emerge in late April and May.

Two or 3 days after the adults emerge, they deposit eggs on the tips of the nuts, Figure 12. Each female may deposit from 50 to 150 eggs. The eggs, which are just visible to the naked eye, are greenish white when they are deposited but assume a reddish appearance a few days later. The first-generation larvae hatch from the eggs in 4 or 5 days and migrate to the buds below the nuts to feed. After a day or two, they enter the nuts, usually at the base, and feed in them, each larva frequently destroying an entire cluster. Bits of frass and webbing may be observed projecting from the injured nuts. Upon reaching maturity, the larvae pupate in the nuts and emerge as adults in June and early July.

The adults deposit eggs in grooves on the tips or bases of the nuts. Second-generation larvae which hatch from these eggs also feed in the nuts. Less injury is produced by this generation because the nuts are larger and each larva requires only one or two nuts to complete its development. Pupation takes place in the hollowed out nuts, Figure 13, and the moths emerge from late July to early September.

A third generation usually follows, but the shells of the nuts have become hard, and only a few of them are penetrated by the larvae. Instead, they feed in the shucks. A number of third-generation larvae construct hibernacula, while the remainder pupate and appear as adults, emerging from late August to October. These adults deposit eggs, which hatch into fourth-generation larvae. If nuts are available, their shucks constitute the principal food of the larvae of this generation. In the absence of nuts, the larvae feed on buds and leaf stems. Overwintering hibernacula are constructed by the partially grown larvae by the middle of November.

Control.—The necessity for control of this pest may be determined by examination of the trees when the shoots appear in the spring. If a number of them are wilted, the following control measures probably will be required.

A spray application should be made when eggs of the first generation appear on the tips of the young nuts in late April or May. The period of egg deposition usually coincides with the completion of pollination, at which time the tips of the nuts turn brown. Satisfactory control may be obtained by using any of several insecticides. See spray schedule, page 4.

Ordinarily, only one application of spray is required to control the nut casebearer. However, if trees surrounding the treated area are not sprayed, moths may enter the sprayed area and a serious infestation of second-generation larvae may develop. Under these circumstances, a second spray may be required in June or early July when second-generation eggs are deposited, .

HICKORY SHUCKWORM

The hickory shuckworm, Laspeyresia caryana (Fitch), frequently causes severe injury to pecans. In the late summer and fall the shucks are tunneled out. As a result, the nuts are slower to mature and the kernels do not develop properly. The shucks stick to the nuts and fail to open, thus increasing the difficulty of harvest.

The adult shuckworm is a dark, grayish-black moth with a wing span of a little over one-half inch. The larva is white with a light brown head. It attains a length of three-eighths inch at maturity.

The winter is passed by the larvae in fallen pecan or hickory shucks. They pupate in late winter and emerge as adults during the spring. The adults deposit eggs principally on hickory trees on the leaves and young nuts, and the larvae feed in developing nuts in early summer.