Table 322 | Diseases and Pests of Trees in Urban Environments American Thuja shoot moth, Thuja mining moth - Argyresthia thuiella |
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Host species | ||
Arborvitae (Thuja spp.), false cypress (Chamaecyparis spp.)
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Symptoms | ||
Already in autumn there is a continuous browning of the leaf scales beginning at the tips - scales translucent. Shoots are mined and contain larvae, in spring pupae. From June on nearly circular emergence holes mostly at the base of the brown shoot parts
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Causal agent | ||
Moth: light grey with brown and grey dots, about 6mm in size; egg deposition in June; young larvae enter leaf scales two weeks later. Larvae: reddish green to brownish green, head black
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Possibilities of errors | ||
Related species of the genus Argyresthia (Juniper mining moth*, Cypress mining moth); Kabatina - blight of Thuja*; other dieback fungi ; Didymascella - leaf blight of Cedar*
*on this sample plate, the links are leading only to the german version without pictures
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Effects | ||
Brown shoots break and cause optical impairment. Repeated heavy attacks may cause death of very young plants
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Control | ||
Control with biotechnical insecticides (insect growth regulators) - no environmental impact, safe. Watch for the precise time of application (a few days after the flight period of the moths in June); control of the flight time possible with pheromone traps
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