Honeydew density in mixed Nothofagus forest, Westland, New Zealand

Abstract

The distribution of the honeydew-producing sooty beech scale (Ultracoelostoma assimile)is very patchy; among the factors reportedly affecting it are host tree species, aspect, and trunk diameter. Honeydew density was examined in May 1989 and January 1990 in 0.6 ha of mixed red (Nothofagus fusca) and black (N. solandri var. solandri) beech forest, 30 km east of Greymouth in Westland. The insect was much more common on red beech (118 m⁻² of trunk in January) than on black beech (4.5 m⁻²), which contrasts with the pattern on the east coast of the South Island. On red beech, there was no significant difference in density on the different aspects of the trunk (north, east, south, or west) inside closed forest. Insect density was related to trunk diameter in red beech, with highest densities on trunks of intermediate size (10–40 cm diameter). The effect of trunk diameter must be allowed for in calculating insect density per hectare. Overall, densities of the insect (89 300–104 400 ha⁻¹) were similar to other data for Westland, but 100 times lower than for N. solandri forest in Canterbury. The scale insect clearly requires much more study.

Keywords:

• honeydew
• beech forest
• Nothofagus fusca
• Nothofagus solandri
• Ultracoelostoma assimile
• Margarodidae
• sooty beech scale insect