Leucoptera malifoliella (Costa)
Taxonomic placing: Insecta, Holometabola, Lepidoptera, Lyonetiidae.
Common name: Pear leaf blister moth, ribbed apple leaf miner.
Geographical distribution: Europe, including the British Isles, the Middle East to China. In Israel since 2000.
Morphology: The white-grey moth is ca 7 mm long with silver-grey forewings that carry two yellow-brownish stripe enfolded within coppery, black and white zones. Hindwings narrow, brown-gray and with long fringes. The pale-green to yellow-brown larva is about 5 mm long, with a dark head and atrophied legs.
Host plants: The pest prefers apples and pears, also infesting the leaves of other deciduous and shade trees, especially of the family Rosaceae.
Life cycle: Winter is passed in white cocoons hidden in bark crevices or attached to dead leaves or debris on the ground. Adults emerge in spring and eggs are deposited singly on the undersides of leaves. The larvae mine concentric, blister-like galleries in the upper leaf layers, leaving them to pupate. Two to four annual generations were reported in the Middle East.
Economic importance: Larval feeding induces the occurrence of round necrotic spots on the upper surface of leaves. Up to 10-15 larvae may attack a single leaf, causing loss of leaf area and even drop. The mines change over time, they become larger, appearing as concentric circles and their color changes from whitish to brown. Fruit is not attacked but heavy leaf loss leads to reductions in size and yield. Heavy leaf losses also reduce the number of blossoms per inflorescence in the following year.
Management
Monitoring: The sex pheromone of L. malifoliella may be used for monitoring. Th injury threshold for control activities in Europe varies between 0.1-2.5 eggs and mines per leaf, depending on the apple variety; no such threshold has been established in the Middle East.
Plant resistance: Apple varieties differ in their susceptibility to the pest, “Red spur” being more susceptible than “Yellow spur”, as seen by fewer mines per leaf and less leaf drop.
Horticultural methods: Weak pruning results in more pest damage than strong pruning techniques, because shoots grow faster and more vigorously after strong pruning. This reduces susceptibility to the pest. Scraping and removing old, loose host tree bark, wherein the moth shelters, reduces the size of the overwintering population.
Chemical control: Applications of Neonicotinoids and neem control the pest.
Biological control: Eulophid parasitoids, especially species of the genus Chrysocharis, significantly reduce pest populations in Europe, unless disrupted by pesticides. The entomopathogenic fungus Beauveria bassiana (Bals.) Vuill. killed almost 70% of the pest in laboratory assays.
References
Baufeld, P. and Freier, B. 1991. Artificial injury experiments on the damaging effect of Leucoptera malifoliella on apple trees. Entomologia Experimentalis et Applicata 61: 201-209.
Draganova, S. A. and Tomov, R. I. 1998. Virulence of a strain Beauveria bassiana (Bals.) Vuill. (Hyphomycetes, Deuteromycotina) against larvae of Leucoptera malifoliella Costa (Lepidoptera, Lyonetiidae). Bulgarian Journal of Agricultural Science 4: 435-439.
Holb, I.J., Gonda, I. and Bitskey, K. 2001. Pruning and incidences of diseases and pests in environmentally oriented apple growing systems: some aspects. International Journal of Horticultural Science 7: 24-29.
Maciesiak, A. and Olszak, R. W. 2002. Efficacy of new insecticides in controlling pear leaf blister moth (Leucoptera scitella Zell.). Progress in Plant Protection 42: 666-668.
Mey, W. 1993. On the parasitism of the pear leaf blister moth Leucoptera malifoliella (Costa) (Lep., Lyonetiidae) in the Havelland fruit-growing area. Journal of Applied Entomology 115: 329-341.
Oppenheim, D., Kuznitzki, W. and Naaman, L. 2003. A new leaf mining moth in Israel, a pest of apple and pear, Leucoptera malifoliella Costa (Lepidoptera, Lyonetiidae). Alon Ha’Notea 57: 368-69, 375 (in Hebrew).
Riba, M., Rosell, J.A., Eizaguirre, M., Canela, R., and Guerrero, A. 1990. Identification of a minor component of the sex pheromone of Leucoptera malifoliella (Lepidoptera, Lyonetiidae). Journal of Chemical Ecology 16: 1471-1483.
Rovesti, L. and Deseo, K.V. 1991. Effectiveness of neem seed kernel extract against Leucoptera malifoliella Costa (Lep., Lyonetiidae). Journal of Applied Entomology 111: 231-236.