- Adult lucerne seed wasp. Photo: L Turton
- Larvae. Photo: L Turton
Adult wasps are shiny black with clear wings and dark brown legs. Wasps lay a single egg into the soft young seed. Minute, white, legless larvae develop and pupate inside the seed.
Green vegetable bug egg parasite. Seed damage is unlikely to be confused with any other lucerne seed eater.
Europe and west Asia, North and South America, Australia. In Australia, the lucerne seed wasp has been reported as a lucerne pest in New South Wales, Queensland, South Australia, Victoria, and Western Australia.
Major - damage more severe in southern growing areas - irregular.
Seed is hollowed out by larvae. Damaged seed does not germinate and are dull brown, dark brown or almost black.
Late summer, particularly for crops grown for seed. Maturing pods are not susceptible to damage.
Adult wasps emerge in spring and lay eggs through the young, soft pod into the soft seed. Once injected into the seed, the egg hatches to a larva which eats out the seed contents and pupates in the hollow seed. A single adult emerges from the seed by chewing a small, circular hole with jagged margins. In summer all stages of the wasp can be found in the field at any one time. In autumn, the pre-pupae enter a winter diapause in the seed until the following spring.
Usually most active in spring. Adult wasps can be detected in crops by sweep-netting. Immature stages can be detected by pulling apart pods and examining seeds with a hand lens.
Any immature lucerne seed wasp detected in the crop destined to be harvested for seed is likely to result in economic loss. Preventative control is necessary in areas with a history of damage by lucerne seed wasp.
Chemical control is only effective against adults. Since emergence is continuous during summer, repeated spraying may induce secondary insects and may not be cost effective. Sprays for other pests may incidentally reduce numbers of lucerne seed wasp adults. For chemical control options see Pest Genie or APVMA.
Cultural control is the most important control method.
Seed damage by lucerne seed wasp to lucerne lines with tightly coiled pods is reported as being less than those with more open pods.