The cork tree has in no wise escaped from disease and infections; on the contrary it has its full allotted share which worries the growers more than the acquiring of a perfect texture, and unless great care is taken will greatly reduce the value of a crop. The larva of the Coroebus undatus (corch) attacks the interior of the cork, penetrating frequently into the tree itself, which causes an undervaluation in the quality of the cork, and, moreover, these perforations unite so closely and in such a manner even in the trunk of the tree that in peeling off the cork, part of the skin of the trunk itself comes off, causing much damage to the tree.

The larva of the Cerambyx cerdo, as well as the ant, Formica rufa L. hormigas, destroys the fine cork with their numerous borings and galleries. Jaspered (Jasperado) is the name by which is known one of the defects of the cork which reduces it greatly in value and as far as can be learned comes from the tree itself. The porosity of cork is greatly increased by the presence of cork-meal, resulting from the disintegration of the Sclerenchyma, or stone cells, which penetrate the cork fiber and falling to a powder facilitate the entrance of infection.[16]