Biologia e técnicas de criação de Trichospilus diatraeae (Hymenoptera: Eulophidae) em pupas de Tenebrio molitor (Coleoptera: Tenebrionidae) e Diatraea saccharalis (Lepidoptera: Crambidae)

Abstract

The potential for Trichospilus diatraeae Cherian & Margabandhu, 1942 (Hymenoptera: Eulophidae) as biological control agent in Brazil is unknown and, therefore, this research assessed the feasibility of pupae of Tenebrio molitor Linnaeus, 1758 (Coleoptera: Tenebrionidae) as host alternative, to optimize its production in the laboratory for the control of Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae). This research was conducted in the laboratory of Entomology of the Federal University of Grande Dourados. Initially, it was evaluated the reproductive performance of T. diatraeae in the host T. molitor by building the table of life and fertility. Host pupae that were individualized with females of the parasitoid in glass tubes. Daily, the pupae were exchanged, until the death of all females. The survival of immatures was 92.65%. The females of the parasitoid had estimated average life of 8.28 ± 1.01 (days), with innate capacity of increase in number of 0.15, net reproductive rate of 37.50; finite rate of increase of 1.16; average time between generations of 23.67 days and time of doubling the population of 4.52 weeks. It appears that pupae of T. molitor are suitable for the development of T. diatraeae. It was subsequently assessed the effect of density on the reproductive capacity of T. diatraeae created in pupae of T. molitor. For this, pupae of T. molitor with 24 hours of age were exposed to parasitism of females of T. diatraeae with 48 hours of age, for 72 hours in host-parasitoid relationships 1:1, 1:7, 1:14, 1:21, 1:28 and 1:32, respectively, with 12 repetitions for each treatment. There are percentages of parasitism of 33.33 and 83.33% for the densities of 1:1 and 14:1, respectively and 100% for the other. The emergence of individuals of T. diatraeae in pupae of T. molitor was 75% in the density of 1:1 and 100% at densities of 21:1, 28:1, 32:1. The cycle length of T. diatraeae ranged from 21.00 ± 2.22 to 24.00 ± 2.00 days for the densities of 32:1 and 1:1, respectively. The progeny of T. diatraeae by pupa of T. molitor was higher in density of 21:1 with an average of 246.50 ± 50.18. The sex ratio decreased with increasing densities of T. diatraeae, ranging from 0.82 ± 0.06 and 0.97 ± 0.01. The proportion of 21 females of T. diatraeae by pupa of T. molitor can be considered more appropriate for the establishment of the parasitoid, due to higher production of offspring in less development time. Then evaluated the reproductive performance of T. diatraeae pupae in the natural host D. saccharalis and alternative T. molitor. Pupae of hosts with 24 hours of age were exposed to parasitism for 72 hours for females of T. diatraeae of 48 hours of age. The duration of the life cycle of T. diatraeae was 20.00 ± 0.00 and 22.89 ± 0.35 days for pupae of D. saccharalis and T. molitor, respectively, with 100 and 80% parasitism and 40 emergency and 75% of this parasitoid on the first and second host, respectively. The progeny of T. diatraeae was 354.00 ± 41.09 and 151.56 ± 30.97 per pupa of D. saccharalis and T. molitor, respectively. The number of individuals of T. diatraeae not completed the development was higher in pupae of D. saccharalis (71.50 ± 19.33). The sex ratio of T. diatraeae in pupae of D. saccharalis and T. molitor showed similar values (0.94 ± 0.01 and 0.93 ± 0.02), respectively. The longevity of females and males of T. diatraeae emerged from pupae of D. saccharalis and T. molitor was (5.93 ± 0.70 and 7.0 ± 1.53) and (12.04 ± 0.69 and 8.4 ± 1.19) days, respectively. In general, the biological characteristics of T. diatraeae were better in pupae of D. saccharalis than T. molitor. The techniques developed have proved suitable for the establishment of T. diatraeae in the laboratory. This knowledge may increase the chances of success of natural enemies in biological control programs for the drilling of sugar cane.