Hover flies: larva are predators of aphids and mites
Aphidius spp. parasitoids of various species of aphids
Trissolcus basalis, egg parasitoid of green vegetable bug.
Hover flies (Syrphidae)Primary Host: aphid and mites Key identifying characteristics: The adult (top) with its black and yellow banded abdomen is often seen hovering above plants. The adults feed on nectar and pollen. The female lays its white oval eggs amongst colonies of aphid or mites. The eggs yield maggots (right) which feed on aphids and mites. The pupa is tear shaped and found under leaves or in leaf litter. Significance: Useful contribution likely.
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Aphidius spp. and other aphid parasitoidsPrimary Host: various species of aphid Key identifying characteristics: The adult wasps are not easily identified in the field. They are sometimes observed working through aphid colonies looking for suitable hosts. The presence of aphid "mummies" (below) amongst an aphid colony indicated that they are active. The female lays its eggs into the body of the aphid. The egg hatches inside and the larva feeds and develops into a fully formed wasp killing the aphid in the process. The aphid body bloats and develops a crusty shell called mummies. When the wasp is ready it cuts an escape hole in the back of the aphid and emerges to mate and feed and the female then searches for aphids to lay more eggs. Significance: These wasps can be a very efficient aphid control especially if they move into the crop early. Look out for aphid mummies while scouting. If, for example, a colony of 20 aphids has a few aphid mummies amongst them, then it is likely that most of the others are also parasitised. |
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Trissolcus spp.Primary Host: Green vegetable bug and some other bug eggs. Key identifying characteristics: Very small black parasitoid. Lay their eggs into bug eggs. Bug eggs parasitised go brown or black. The shells of unparasitiesed eggs from which bugs have emerged are white. Egg rafts can be collected in a vial and then observed to see whether bugs or wasps emerge. Right, wasp just emerged from GVB egg. Significance: Occurs in many areas. How much it contributes to the suppression of GVB in sweet corn is unknown.
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