Individual study: The consequences of ant-attendance to the biological control of the red wax scale insect Ceroplastes rubens by Anicetus beneficus
Itioka T. & Inoue T. (1996) The consequences of ant-attendance to the biological control of the red wax scale insect Ceroplastes rubens by Anicetus beneficus. Journal of Applied Ecology, 33, 609-618
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Exclude ants that protect pests
A replicated, controlled study in 1989-1991 in Wakayama Prefecture, Japan (Itioka & Inoue 1996) found more parasitism of red wax scale Ceroplastes rubens by first generation wasps Anicetus beneficus on twigs where black garden ants Lasius niger were excluded with glue barriers (14% scale insects parasitised) than on twigs without glue barriers (5% parasitised). Second generation wasps parasitised marginally more scales (13.5%) on twigs with than without barriers (8%). Red wax scale survival rate was lower on twigs with (2.1%) than without (4.6%) ant barriers. Twigs with barriers had 1,582-3,122 young scales and 13-64 egg-laying adult scales, compared with 2,791-4,028 young and 166-187 egg-laying adults on twigs without barriers. Scale population increase was 10 times less on twigs with than without barriers over two years. A pair of one-year old twigs was selected on each of 12 satsuma mandarin Citrus unshiu trees in a 1 ha orchard area in June 1989. One twig in each pair received glue at the base of the stem to exclude ants. Scales were counted in August-October 1989 and in May-June 1990 to assess parasitism, which was determined by body colour. The experiment was repeated on nearby twigs (in the same trees) in 1990-1991.