Forest Pests: Insects, Diseases & Other Damage Agents

Csóka, György (2003): Levélaknák és levélaknázók - Leaf mines and leaf miners. Hungarian Forest Research Institute. Erdészeti Turományos Intézet, Agroinform Kiadó, Budapest, 192 pp.

Many generalist predatory insects are known the prey on leaf mining larvae. Hornet (Vespa crabro), and other smaller wasps frequently open the larger blotch mines (i.e. Profenusa pygmeae) and remove larvae and pupae. Some wasp are specialised to feed on leaf miners. Predatory bugs, soldier beetles and ants consume leaf miners in large numbers. Ants cause particularly high mortality, when aphid colonies can be found close to mined leaves. The frequently visit these colonies for honey dew and also open the mines near their way. Many ground beetle species feed on larvae and pupae in leaves fallen on the ground. The small adults of leaf miners are consumed by spiders, earwigs and ants.

Insectivorous birds, particularly tits often feed on leaf miners. They prefer the larger, fully developed larvae and pupae of leaf mining moths and sawflies, especially if their local abundance is high enough. Because of the small size of leaf miners preying on them at a low abundance level would not be profitable.

From point of impact on populations, parasitoid insects play the most important role as natural enemies of leaf miners. Some cases they cause more than 90% mortality. Parasitoids of leaf miners can be found nearly exclusively among Hymenoptera. The size of a parasitoid is strongly determined by the size of its host. Because of small size of leaf miners, their parasitoids are also small. Most numerous group of them are chalcids (superfamily Chalcidoidea), but species belong to Ichneumonidae and Braconidae also parasitise leaf miners. In all three groups secondary and tertiary parasites are also found. These feed on the parasitoids of the leaf miners, instead of the leaf miner itself.

From point of leaf miners as hosts Eulophidae is the most species rich family of chalcids. Ca. 70 % of chalcids are endoparasites (developing inside the host) and 30% are ectoparasitic (developing on the body surface of the host - see page), Most of the leaf miner parasitoids are either polyphagous or oligophagous. The strict specialists are less common among them. Generally the parasitoid assemblages of leaf miners living on trees are richer than those of herbaceous plants. While the parasitoid communities of leaf miners on woody plants are regularly dominated by poly- and oligophagous species, in communities on herbs specialist parasitoids can play more important roles.

It is a very interesting process, how the native parasitoids get used to the introduced and spreading leaf miners. Their parasitism rate usually increases with increasing time has elapsed since the introduction of the new host. This "learning" process can be relatively fast if the newly arrived leaf miner has many close relatives with similar life history in the new homeland (see Phyllonorycter robiniella on page…). If the invading new species has hardly any relatives with same or similar life history, this process will be considerably slower (see Parectopa robiniella on page…), and the parasitoids will not become able to regulate the host's population for a long time.

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