Enemies.
While a number of insects and fungi infest coffee plantations to a greater or less extent, the crop is remarkably free from serious annoyance. In Hawaii there are no serious diseases or insect pests, the torpedo bug (Siphanta acuta) and the brown-eyed disease (Ccrcospora coffeicola) of leaf and berry being the most troublesome. Both are readily amenable to preventive measures, the best preventive being thorough cultivation, the proper degree of shading, and the use of fertilizers. The coffee blight (Pulvinaria psidii) has done serious damage in some districts. It seems to occur prin cipally in neglected plantations. It will probably continue to be a pest, since it infests also the guava and certain ferns. Nematode worms are often present in the roots, and rarely occur in the stem and berry, causing the latter to drop before matu rity. A "black fly" (aphid) is abundant on new growth in Hawaii.
Porto Rico is not so fortunate in the point of numbers of enemies, but is comparatively free from serious annoyance. The diseases and insect pests thus far observed are as follows: Coffee leaf blight, provisionally called by F. S. Earle, Sclerotium sp., is a fungus which covers the trees from the roots up with brownish mycelia) threads, spreading out, as the leaves are reached, into a fine white weft. The attacked leaves blacken soon and fall. The remedy is plenty of sunlight and spraying with Bordeaux mixture.
Stilbum flavidum, so-called American coffee dis ease, is a fungus making on the leaves nearly round spots of about one centimeter in diameter and of a yellowish color, causing the leaves to drop. Reducing excessive shade is recommended as a remedy. Lately the same fungus has been discovered on the fruit, causing blackened spots on the pulp and seeming to eat its way into one of the kernels, on the parchment of which it causes wart-like growths which extend to the kernel itself. Spraying with Bordeaux mixture is being tried.
These diseases, as well as coffee root-rot, do not occur frequently, however, and mostly in too moist and overshaded localities.
Coffee leaf-miner (Leucoptera cqffeella) is perhaps the most serious coffee pest thus far observed. It
is a minute silvery moth, which in its larval state burrows within the leaf tissues, causing brown, dead patches on the leaves. Sometimes more than one larva is found in the same patch, and the leaves are sometimes covered witli such patches, thus seriously deranging the nutrition of the plant. On rich soil the harm is not very apparent, but must certainly influence the crop. On poorer soils the leaves drop off, leaving the trees entirely leafless or with only a pair of small leaves at the point of each branch, thus giving the growth of the plant a tremendous setback. Hand-picking and burning the attacked leaves have been resorted to, but without result ; as soon as new leaves are formed they are again and again attacked. Thus far the only remedies are its natural enemies (discovered on the island in 1904 by 0. W. Barrett), Chryso Maris livida, and Zagrammosoma multilineata, parasites, the larvm of which are found inside the coffee leaf-miner on which they feed, and an apparently fungous disease which attacks the miner in its larval state. It has been estimated that the leaf-miner is responsible for the loss of upwards of $100,000 worth of coffee in Porto Rico annually.
Coffee scale (Lecanium hemisphericum) is present everywhere. It sometimes occurs so plentifully on the tender twigs that they seem to dry out, but this is very seldom, and the harm from the scale is not otherwise apparent. Larva; of lady-birds, and a white fungous disease which seems to grow in the bodies of the scale, spreading over all the scale on the same twig or stem or plant, seem to be sufficient to hold the scale in check.
Weevils do much harm in some places by eating the young leaves, and by attacking the green soft parts of the twigs, in some instances causing those parts bearing the fruit to drop or die. The most damage apparently is done in young coffee. Mealy bugs sometimes appear at the roots of old trees. May beetles dig holes in the earth near the stem and their larvm do damage to the roots. Other larva?, bugs, rats and ants attack the coffee plant, but none of them is serious.