Kuno Scale

Kuno scale is a pest of plum and other stone fruits.

Like other soft scale, kuno scale (Eulecanium kunoensis) is a sap-sucking insect that hides under a dome-shaped protective barrier. Unlike armored scales, which can be separated from their dome, kuno and other soft scales are attached to their dome.

​Kuno scale description

Kuno scale females are 1/6 of an inch in diameter and a dark, shiny brown. They actually look like tiny beads on tree stems, during summer. Just before egg production, they turn yellow or orange, with black markings. During winter, they are more flattened and less shiny. If you remove a kuno scale from its host, you will see a visible lip on her body, which is used as a point of attachment. Nymphs are flattened, and either brown or yellow. Male cocoons are 1/12 of an inch long and translucent.

Kuno scale lifecycle

Eggs hatch under their mother in spring. These first instar nymphs are called ‘crawlers’ because they crawl away from her and find a place to feed on leaves throughout the summer, going through multiple instars as they feed. In fall, mature nymphs find a hiding place on twigs just before leaf fall. These nymphs overwinter on twigs and reach adulthood in spring, just in time to lay more eggs.

Kuno scale damage

As a sap-sucking insect, Kuno scale sucks phloem sap from twigs and leaves. While it prefers plum trees, Kuno scale can also be found on peach, cherry, nectarine, apricot, and almond, as well as rose, walnut, and pyracantha. These pests can populate an area so quickly, that it can seem as though they appeared overnight. Plants may appear water stressed. Heavy infestations can lead to twig dieback and premature leaf drop. Also, Kuno scale produces a lot of honeydew (sugary poop). Honeydew is the perfect growth medium for sooty mold. It also attracts ants, which will protect and farm Kuno scale. If you see ant trails on your plum tree, make a point of finding out where they are going in your tree.

Kuno scale control

Since ants protect Kuno scale from natural predators, blocking ants from getting up in your trees is the easiest control measure. To do this, simply wrap the tree trunk with a sticky barrier. You can also apply horticultural oil to twigs and the ends of branches just as buds are swelling, in spring. You can also try drenching the undersides of leaves in early summer, but this is tricky, because it’s not a good idea to spray dormant plum or walnut trees with oil, especially during periods of drought.

​And, let’s face it, spraying the underside of leaves is a royal pain.