Leafminer

Various leafminer species create pale, winding or blotchy tunnels within leaf tissue of alder, willow, poplar, and other host plants starting in spring. The miners are small larvae that feed between leaf surfaces, leaving papery trails as they consume leaf tissue. You identify the problem by the distinctive mining patterns visible on affected leaves; heavy infestations can cause significant leaf yellowing and drop.

Monitor host plant foliage starting in May for early mining appearance. Remove and destroy heavily mined leaves by hand to reduce overwintering populations. For valuable plants, apply horticultural oil in late winter to target pupae and overwintering stages. Once mining damage appears, spinosad or neem oil applied to undersides targets young larvae.