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Viability of Nezara viridula (L.) eggs for parasitism by Trissolcus basalis (Woll.), under different storage techniques in liquid nitrogen

Viabilidade de ovos de Nezara viridula (L.) ao parasitismo por Trissolcus basalis (Woll.), sob diferentes técnicas de armazenamento em nitrogênio líquido

Different egg conservation techniques were assessed under low temperature conditions to multiply the parasitoid of stink bug eggs Trissolcus basalis (Woll.) (Hymenoptera:Scelionidae). Masses of fresh Nezara viridula (L.) eggs were stored for 12 months in liquid nitrogen (-196ºC), wrapped in aluminum foil, in microcentrifuge tubes ("eppendorf") or in vacuum sealed double plastic bags (500 eggs/technique/month). Every 30 days, 10 egg masses from each of the different storage techniques, were taken out, thawed immediately and subjected to parasitism by T. basalis. Green stink bug eggs, stored at -196ºC presented conservation conditions and viability for T. basalis development, with high parasitism rates and emergence in the eggs stored under the three different techniques. Parasitism of eggs stored wrapped in aluminum foil (95.4%), in tubes (92.3%), and under vacuum (93.7%) were statistically equal to parasitism in fresh eggs (97.3%). Egg viability, expressed by the rate of emergence of adult parasitoids, indicates that the three techniques studied provided excellent T. basalis development and emergence conditions with no significant differences when compared with fresh eggs. Throughout the total storage period (12 months) there was no reduction in the number of females hatched, although there were fluctuations in the sexual ratio for some periods. These results make green stink bug egg conservation, and later multiplication of the parasitoid T. basalis possible for a period twice as long as that known and used today.

Insect; biological control; stink bug egg conservation; low temperature; parasitoid


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