Exigências térmicas e estimativa do número de gerações de Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae), para regiões produtoras de crucíferas em Pernambuco | Thermal requirements of Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae) and estimation of the number of generations in crucifers in Pernambuco State, Brazil
Ferreira, Suêrda W.J. | Barros, Reginaldo | Torres, Jorge B.
This research was carried out to determine the thermal requirements of Oomyzus sokolowskii (Kurdjumov) reared on the diamond back moth (DBM), Plutella xylostella (L.), and to estimate the number of generations under laboratory conditions in crucifers growing in Pernambuco State, Brazil. Fourth instar DBM larvae were exposed to parasitism by O. sokolowskii for 24h and maintained at the following temperatures: 15, 18, 22, 25, 28, 30, and 33ºC. Duration of O. sokolowskii immature phase (egg-larvae-pupae) was temperature dependent, ranging from 12.9 to 31.6 days, at 28ºC and 18ºC, respectively. Survival of O. sokolowskii immature phase was also influenced by temperature, being higher (77.2%) at 28ºC. Temperatures below 22ºC and above 28ºC were shown inadequate to rear the parasitoid. The number of adults emerged from DBM pupae was not affected by temperature and ranged from 7.3 to 12.0. The sexual ratio ranged from 0.86 to 0.91 and did not present difference among the temperatures. The lower threshold temperature (Tb) and the thermal requirements (K) for immature phase of O. sokolowskii were 11.6ºC and 211.8 degree-days, respectively. Comparison of these results to P. xylostella thermal requirements (Tb = 8,85ºC and K = 299,67 GD) denotes that along the year, the number of generations of O. sokolowskii is always higher than that of P. xylostella, evidencing that O. soklowskii could develop up to 24 generations an year, while DBM could reach 20 annual generations.
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