The parasitic wasp Dacnusa sibirica occurs naturally in Europe and North America. The adult is dark brown to black and is 2-3 mm long. It can easily be distinguished from Diglyphus isaea by its long antennae. As an adult, it differs from Opius pallipes, another beneficial insect against leafminers, only in the front wing venation.

The female deposits her egg in a leafminer larva, preferably in the 1st or 2nd instar. The egg is laid in the larva, not beside the host (as Diglyphus does). Therefore, it is called an endoparasite. Only if there are too few hosts, Dacnusa sibirica may deposit more than one egg per larva (superparasitism), but eventually only one parasitic wasp develops in the leafminer larva.

The parasitized leafminer larva does not die, but keeps on feeding. The first instar of Dacnusa sibirica evolves in the leafminer larva. Only when the leafminer larva pupates does the Dacnusa larva mutate to the 2nd instar. Further development into the 3rd instar and the pupa also takes place in the leafminer pupa. Finally, not a leafminer, but an adult parasitic wasp leaves the pupa. So the different development stages are not visible without opening the leafminer larva or pupa.

The development of Dacnusa sibirica takes 17.5 to 19.4 days (depending on the host development stage) at 20°C (68°F). For the leafminer L. bryoniae it takes 26.5 days at this temperature. At lower temperatures, the parasitic wasp benefits an even greater difference in development time with the leafminer. At 25°C (77°F) an adult wasp lives for 7.4 days and deposits an average of 48 eggs, while at 15°C (59°F) this mounts up to respectively 20.2 days and 225 eggs.

Dacnusa sibirica can hibernate in leafminer pupae. In this way the wasp can occur simultaneously with its host already early in the season. Adult parasitic wasps do not feed on hosts as Diglyphus isaea does.

Dacnusa sibirica is able to locate mines at very low densities. It looks mainly low in the crop. Once it has found a mined leaf, it searches for larvae with its antennae. The wasp can distinguish parasitized from non parasitized leafminer larvae (host discrimination).

Dacnusa sibirica is used in a wide range of crops to prevent leafminer damage, both on vegetables (tomato, sweet pepper, lemon, lettuce, ...) and on ornamentals (gerbera, chrysanthemum, ...). Dacnusa effectively controls the tomato leafminer, the serpentine leafminer and the pea leafminer. In this regard it differs from the closely related Opius pallipes, of which the eggs are encapsulated by the serpentine leafminer. Therefore, control of this leafminer species is poor with Opius pallipes.

Thanks to the ability to hibernate in leafminer pupae, Dacnusa sibirica can occur in the early season together with its host. The importance of this spontaneous parasitation differs from case to case, but is seldom sufficient for a good control. For early detection of the first leafminers, yellow sticky cards (BUG-SCAN®) are a useful tool. Research has shown that more leafminers are caught if the sticky cards are placed horizontally close to the ground level than when hung vertically.

At first signs of mines or feeding spots on the leaves, Biobest advises to introduce weekly the Dacnusa-Mix-System (90% Dacnusa + 10% Diglyphus) at 0.25 wasps/m² until sufficient parasitation. As parasitation is not directly visible, one should take some pupae samples in a glass jar or bottle, and wait and see if a leafminer or a parasitic wasp comes out. By counting the number of emerged wasps and leafminers, one knows the parasitation percentage.

Later in the season or in Mediterranean climates it is recommended to release Diglyphus isaea only. This parasite controls leafminers better at higher infestation levels and higher temperatures.

The parasitic wasps are supplied in tubes (with screw cap) of 250 adults, of which 90% are Dacnusa sibirica and 10% are Diglyphus isaea.

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