Nidularia is a very rare cochineal insect in our country. However, it can strongly affect very stressed holm oaks. It is a hemiptera/ homoptera insect that is biologically very similar to the Kermes; the female is yellowish brown colour in its early stages, and then turns dark brown (Fig. a
The damage is caused by nymphs that come out from under the shell and, unlike Kermes, colonise parts of the trunk and main branches (Fig. b
), feeding on the sap through suction mouth pieces. These insects aggravate the weakness of trees and make them more prone to other attacks by new pathogens.
As this is an infrequent plague that does not systematically affect trees every year, like aphids, curative treatments are always more likely. The optimal time for treatment should be when the first instar nymphs emerge. This way, they can be eliminated and damage and future generations avoided.