What's eating my astilbe chinensis 'pumila'?

Astilbe chinensis 'Pumila' is largely deer- and slug-resistant, but vine weevil grubs attacking roots are the real danger. Spider mites and aphids can also target foliage in hot, dry spells. Fortunately, serious pest pressure is uncommon; good soil moisture and air circulation keep most problems at bay.

C-shaped grubs silently devour roots below soil; plants wilt and collapse without obvious above-ground cause. Apply pathogenic nematodes (Steinernema kraussei) to moist soil in late summer or spring when soil is above 5°C (41°F). Remove adults found on foliage at night.

Tiny pale stippling on leaflets, fine webbing on undersides; foliage turns dull bronze-yellow in hot, dry summers. Blast foliage with water to knock mites off. Apply insecticidal soap or neem oil spray, covering undersides of leaves. Improve air circulation.

Clusters of small soft insects on new growth and stems; distorted young shoots and sticky honeydew residue. Rub off small colonies by hand or use a strong water jet. Insecticidal soap spray is effective. Encourage ladybirds and lacewings as natural predators.