Casemakers and skeletonizers—Bucculatrix spp.
The oak ribbed casemaker is probably the most common leafminer on deciduous and live oaks throughout California. Its common name refers to its white, cigar-shaped cocoons, which have distinct longitudinal ribs. Other similar species include the oak leaf skeletonizer on oak and chestnut, birch skeletonizer on birch, and B. pomifoliella, which infests hawthorn and flowering fruit trees. Adults are mottled white, brown, and black. Mature larvae are olive green with rows of pale spots. There are two generations a year for each species, one each in the spring and summer, except for the birch skeletonizer, which has one generation.
Bucculatrix cocoons occur on host tree bark, leaves, and nearby plants and objects. First-instar larvae mine inside the leaf. Later instars feed externally on the lower leaf surface. Damaged foliage between leaf veins appears translucent.
No control is generally warranted for Bucculatrix in landscapes. Intolerable populations may be reduced by a foliar insecticide application that thoroughly covers the lower leaf surface when larvae are observed feeding there. However, spraying broad-spectrum, persistent insecticides can induce outbreaks of other invertebrate pests.
Elongate pupal and round larval cocoons
Brown patches caused by casemaker larvae