About this Tree Concern
Boxwoods are planted as ornamentals and typically used for edging, as hedges, and/or clipped into different shapes to make topiaries (Figure 1). However when infested, the plants are disfigured by the loss of leaves, by webbing spun by the larvae, as well as larval excrements (Figure 2). Larvae feed principally on leaves of the host but may also attack the bark.
Box tree moth was detected in Toronto in August 2018 by a citizen scientist as reported in an online publication (see iNaturalist.org's Blog). In November 2018, the Canadian Food Inspection Agency (CFIA) confirmed the presence of box tree moth in an urban neighbourhood in Toronto. This is the first confirmed report of this pest in North America and the source of its introduction is unknown.
Remediation
Box tree moth eggs are laid in clusters, and greenish yellow in colour when first laid. Black dots start to show as the larval head capsule is forming. Eggs hatch in about 3 days. On hatching, larvae are greenish yellow in colour with a shiny black head. As they mature, they become more greenish and develop a striking pattern of thick black and thin white stripes along the length of the body that can be up to 4 cm long.
Adults are described as medium-sized moths with a wing span of about 4 cm. Two colour variants have been recognized. The more common variant has white coloured wings with thick dark brown border trimmings. The ‘melanic' variant is less common and has brown wings with small white streak on the forewing.
Preventing spread can be achieved by not moving infected boxwoods. In Europe, chemical treatments and biopesticides are available for use on boxwood; however many of these compounds are not currently be registered for use on boxwood or available in Canada.