What's eating my darwin's barberry?

Darwin's Barberry is a robust, thorny evergreen shrub with few serious pest problems. Aphids occasionally colonize new spring growth, and scale can establish on older stems. Its dense spiny habit deters most browsing animals. Aphids are the most frequent visitor; a strong water jet or a round of insecticidal soap is usually all the control needed.

Clusters of small soft-bodied insects on new shoot tips in spring cause curled, discolored leaves and sticky honeydew; populations typically self-limit once natural predators build up. Dislodge with a strong water spray. Apply insecticidal soap or neem oil to affected tips every 4–5 days. Avoid broad-spectrum pesticides that kill the beneficial wasps and ladybugs that naturally limit aphids.

Hard brown or gray bumps on stems and branches; heavy infestations reduce plant vigor, cause yellowing of older leaves, and can lead to stem dieback if left untreated. Apply horticultural oil at the correct dilution to coat stems thoroughly; treat in late winter for dormant egg masses or in summer to kill crawlers. Prune out and destroy heavily encrusted stems.

Irregular scalloped notches on leaf margins from adult beetles feeding at night; white grubs in the soil chew roots, which can stress or kill container-grown specimens. Apply Steinernema kraussei nematodes to moist soil in late summer or autumn. Check the compost of pot-grown plants if unexplained wilting occurs and remove any grubs found. Use physical barriers (gravel mulch) to deter egg-laying adults.