Caliroa cerasi L.
(Sometimes known as Eriocampoides cerasi Retz).
Common name: Pear sawfly, pear slug, pear and cherry slug sawfly.
Geographical distribution: Almost cosmopolitan, occurring wherever pears are grown.
Morphology: The larva is flattened, 9-11 mm long, with a slimy dark-green coating over its greenish body (thus “slug”), an enlarged thorax and 10 pairs of legs. The adults are black and yellow, about 6 mm in length, the wings are almost transparent, with a slightly darkened median band.
Host plants: Rosaceous fruit crops, especially pears.
Life history: This sawfly may be univoltine, bivoltine or multivoltine, depending on the geographical region. The mature larvae overwinter in diapause within their cocoons in the soil, pupate in the spring and emerge. The parthenogenetic females lay their eggs (about 75/female) in the lower side of the host leaves. The emerging larvae feed on the leaves’ upper side, seldom touching the veins or lower epidermis and drop to the soil as they mature.
Economic significance: The pear slug is an important pest of pears as well as of plums and cherries. The larvae skeletonize the foliage, leaving behind only the veins, imparting a silvery look to the leaves. The injury of the univoltine pest may affect fruit size at maturity, whereas damage of the second generation causes extensive pear defoliation, reducing tree growth and the yield of the following year. Pest infestation is more damaging to young trees.
Monitoring: Sticky traps are used for monitoring pest emergence from the soil, for determining the best time for pesticide applications.
Plant resistance: Pear cultivars that are partially resistant to the pest are in use in New Zealand.
Biological control: Many natural enemies of this pest are known from different regions. They include predatory Pentatomidae, endoparasitoids like Lathrolestes luteolator (Gravenhorst), Ichneumonidae, Eulophidae like Cirrospilus vittatus Walker, the egg parasite Trichogramma sp. (Trichogrammatidae), Bacillus thuringiensis (Bt) and the entomopathogenic fungus Beauveria bassiana (Bals.-Criv.) Vuill.
Carl, K.P. 1972. On the biology, ecology and population dynamics of Caliroa cerasi (L.) (Hym., Tenthredinidae). Zeitschrift für Angewandte Entomologie 71: 58-83.
Carl, K.P. 1976. The natural enemies of the pear-slug, Caliroa cerasi (L.) (Hym., Tenthredinidae), in Europe. Zeitschrift für Angewandte Entomologie 80: 138-161.
Miles, H.W. 1935. Biological studies of certain species of Caliroa Costa and Endelomyia Ashmead (Hymenoptera: Symphyta). Annals of Applied Biology 22: 116-133.
Shaw, P.W., Brewer, L.R., Wallis, D.R., Bus, V.G.M. and Alspach, P.A. 2003. Susceptibility of seedling Pyrus clones to pear sawfly (Caliroa cerasi) (Hymenoptera: Tenthredinidae) damage. New Zealand Journal of Crop and Horticultural Science 31: 9–14.
Wearing, C.H., Marshall, R.R., Attfield, B.A. and Colhoun, K. 2011. Insecticidal control and the phenology of cherryslug (Caliroa cerasi (L.)) (Hymenoptera: Tenthredinidae) on organic pears in Central Otago. New Zealand Journal of Crop and Horticultural Science 39: 187-201.
Zajanckauskas, P. and Ryliskiene, M. 1979. Bioecology of the cherry slug (Caliroa limacina Retz.) in orchards of the Lithuanian SSR. Acta Entomologica Lituanica 4: 127-140 (in Lithuanian with an English summary).