Canadian Forest Service Publications
Predation on Mindarus abietinus infesting balsam fir grown as Christmas trees: the impact of coccinellid larval predation with emphasis on Anatis mali. 2000. Berthiaume, R.; Hébert, C.; Cloutier, C. BioControl 45: 425-438.
Issued by: Laurentian Forestry Centre
Catalog ID: 20436
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The impact of natural coccinellid larval predation on the balsam twig aphid was evaluated by systematically removing coccinellid egg masses in a 6–8 year-old balsam fir (Abies balsamea) Christmas tree plantation in southwestern Quebec. Among coccinellid species hunting on fir foliage during development of Mindarus abietinus fundatrices in May, the indigenous Anatis mali was by far the most abundant and the main one to oviposit on trees. Comparison of trees on which coccinellid larval predation was excluded with control trees showed that A. mali had a marked impact both during and after the phase of rapid M. abietinus population growth that followed fundatrix maturation. On trees where coccinellid larvae were allowed, aphid colonies became inactive (i.e. no live aphids in the colony) about two weeks earlier than on controls. A strong dampening effect on aphid density was also observed in those colonies that remained active until the end of the aphid life cycle. Predation on aphid colonies reduced sexuals production, as the density of M. abietinus overwintering eggs per shoot subsequently was reduced by 32%. Predation by coccinellid larvae occurred too late to prevent needle damage to current year shoots, which affects the aesthetic value of Christmas trees. However, current year shoots measured in the mid-crown of trees late in the season were 19% longer on trees where aphid predation by coccinellid larvae was allowed, compared with trees where they were excluded. Rearing all larval stages of A. mali on 4th instar and adult sexuparae of M. abietinus indicated an average consumption of 269 aphids to complete larval development and pupate, which was equivalent to at least seven colonies of M. abietinus at maximum aphid density at the experimental site. Anatis mali is an important natural control factor of balsam twig aphid in Christmas tree plantations, hence its activity should be protected and possibly stimulated by favourable pest management practices.