Olives, plum, pear, and apple
The olive scale, Parlatoria oleae is a soft scale insect belonging to the Coccidae family. Adults are 2-3 mm long with oval, reddish bodies covered by a waxy layer that gives them a grayish-white color. Adult females cover their eggs and remain mostly immobile. The first instars (“crawlers”) emerge from the eggs and immediately search for a spot to feed on. Olive scale feeds on twigs and leaves, but it prefers to feed on fruit when fruit is present.
Infested fruits will develop purple spots that are most likely noticed during harvest time. The formation of purple spots on green fruits makes them unsuitable for most markets. Intense infestations can significantly lower tree productivity.
Chemical control of olive scale revolves around pyriproxyfen-based products, which is an insect growth regulator. For this reason, application timing is crucial because insecticides are effective only against the crawlers (the most sensitive stage of the olive scale). Therefore, spraying applications should take place when crawlers emerge.
One can use traps to determine when crawlers are hatching. In spring, take transparent tape that is sticky on both sides and encircle several branches of infested trees. Change the sticky tape on a weekly basis. Use a hand lens to identify the crawlers; they will stick to the tape and look like tiny yellow dots.
Olive scale can be effectively controlled by the natural enemies Aphytis maculicornis and Coccophagoides utilis, which are commonly found in many regions. Make an effort to protect natural enemies by selecting insecticides that do not kill beneficial insects. Minimize the use of insecticides with carbamates, organophosphates, and pyrethroids as much as possible.
*Names marked in red are considered to be highly poisonous to beneficial insects.
*Names marked in green are considered to be organic and IPM (integrated pest management) compatible.