Xylosandrus compactus (Eichhoff)

Bustillo, Alex, 2015, Part II. Pests, Compendium of Coffee Diseases and Pests, United States of America: The American Phytopathological Society, pp. 45-60 : 57-58

Xylosandrus compactus (Eichhoff) ( Coleoptera : Curculionidae )

adult females are 1.4-1.9 mm long and 0.7-0.8 mm wide. They have a stout, cylindrical, elongated, brown to black body; distinct punctures on the pronotum posterior; a transversely oriented hair tuft at the pronotum base; and long setae. The adult male is 0.8-1.1 mm long and 0.4-0.5 mm wide; has a rounded, dwarfed, reddish brown body; and is flightless and rare. Eggs are small (0.3 x 0.5 mm), white, and ovoid. A mature larva is about 2 mm long and has a pale brown head capsule and a creamy white, legless body. A pupa is about as long as an adult and has a creamy white body and a typical exarate form.

The tiny, brownish black, cylindrical beetle is a type of ambrosia beetle, and it attacks both the lateral and vertical branches. Eggs are laid approximately 7 days after the female enters the twig. The egg stage lasts 4 days, the larval stage lasts 11 days, and the pupal stage lasts 7 days. Adults harden the tegument in about 2 days and the female reaches sexual maturity in 6 days. Mated females bore into the twig, make a tunnel for eggs, and grow food for larvae. The female carries a fungus, Fusarium solani (Mart.) Sacc. , which she cultivates within the tunnel to feed her larvae. This fungus produces a toxin that kills the twig and the leaves beyond the entrance hole. Eggs are laid in groups of 8-15. Larvae spend all of their life inside the gallery, passing through two instars and feeding on the conidia of this ambrosia fungus.

Damage

X. compactus is commonly found on Coffea canephora Pierre ex A. Froehner , and although it is not a serious pest, infestations on individual plantations can be severe. Typical symptoms of black twig borer attack are withered or dried branches with shot holes. The attacked tissue collapses and terminal leaves beyond the point of attack fall off prematurely. The circular entry hole, less than 1.6 mm in diameter, is usually located between the last healthy leaf and the first wilted leaf on the dying lateral. Although a single beetle hole may kill a twig, several burrows are often required before the lateral branch dies. On the thicker vertical trunk, even heavy infestations do not always kill the branch. This beetle generally attacks trees weakened by drought, girdling, heavy pruning, standing water, or lack of fertilizer. Some coffee cultivars are more susceptible than others.

Population Management

The best control is maintaining healthy trees. Infested laterals should be pruned 5-8 cm below the hole as soon as wilting is observed because new adults will emerge in a few weeks. Pruned laterals should immediately be chipped, burned, or buried to kill the beetles and the larval stages. Light shade and good drainage must be maintained. Simply cutting off the wilted lateral and leaving it on the plantation does not kill the adult or young. They will leave the branches and move to another tree. None of the insecticides registered for coffee is effective against this pest.