Dispersal of Cotesia flavipes in sugarcane field and implications for parasitoid releases

Abstract

Diatraea saccharalis Fabr. (Lepidoptera: Crambidae) is a major sugarcane pest in Brazil. The management of infested areas is based on the release of Cotesia flavipes (Cameron) (Hymenoptera: Braconidae), a parasitoid of D. saccharalis larvae, but there are doubts about the effectiveness of C. flavipes, primarily regarding its rate of dispersal in sugarcane fields. Thus, the objective of this study was to evaluate the dispersal of C. flavipes in a sugarcane field and suggest a release method that provides higher parasitoid efficiency. The study was carried out in four areas of approximately 1 ha, in which stalk pieces containing 20 D. saccharalis larvae were distributed in a rectangular grid, and 12,000 C. flavipes adults were released at four points, that were 50 m apart and 25 m from the field border. Three days later, the D. saccharalis larvae were recovered and kept in the laboratory until they reached pupal stage or C. flavipes emergence. Parasitism varied from 13.2% to 42.8%. The random distribution of parasitized larvae was found in one assay. In three areas, the parasitized larvae showed an aggregated distribution, with a range of 15 to 25 m. Since the parasite's success is directly linked to parasitoid dispersion, it would be interesting to move the release points to 30 m from each other because the dispersal may happen in a 15 m radius.Key words: sugarcane borer, Diatraea saccharalis, biological control, aggregation, pest management. Dispersão de Cotesia flavipes em canavial e implicações para a liberação do parasitoideResumo Diatraea saccharalis Fabr. (Lepidoptera: Crambidae) é uma das principais pragas da cana-de-açúcar no Brasil. O manejo de áreas infestadas é baseado na liberação de Cotesia flavipes (Cameron) (Hymenoptera: Braconidae), um parasitoide de larvas de D. saccharalis, mas existem dúvidas a respeito da eficiência de C. flavipes, principalmente em relação à sua capacidade de dispersão em campo. Assim, o objetivo deste estudo foi avaliar a capacidade de dispersão de C. flavipes em canaviais e sugerir um método de liberação que propicie maior eficiência do parasitoide. O estudo foi conduzido em quatro áreas de aproximadamente 1 ha, e, em cada uma, pedaços de colmos contendo 20 larvas de D. saccharalis foram distribuídos em grid retangular e 12 mil adultos de C. flavipes foram liberados em quatro pontos, separados entre si por 50 m e a 25 m das bordaduras do campo. Três dias depois, as larvas de D. saccharalis foram removidas e mantidas em laboratório até se transformarem em pupas ou até a emergência de C. flavipes. O parasitismo variou de 13,2% a 42,8%. As larvas parasitadas se distribuíram ao acaso em uma área e em três áreas a distribuição foi agregada, com alcance de 15 a 25 m. Visto que o sucesso do parasitismo está diretamente ligado à dispersão do parasitoide, sugere-se que os pontos de liberação estejam distantes entre si 30 m, visto que o raio de dispersão pode ser de 15 m.Palavras-chave: broca-da-cana, Diatraea saccharalis, controle biológico, agregação, manejo de pragas.

Systematics and biology of Cotesia typhae sp. n. (Hymenoptera, Braconidae, Microgastrinae), a potential biological control agent against the noctuid Mediterranean corn borer, Sesamia nonagrioides

“…Larvae also defend themselves by biting to death the wasps attempting to oviposit, killing 30-40% of them (Potting et al 1997). Dispersion of these small parasitoids may also limit their efficiency, and would explain why mass releases of C. flavipes performed in sugarcane fields in Brazil successfully raised the parasitism rate to a range of 40-60% (Botelho and Macedo 2002; Dinardo-Miranda et al 2014). Our data on C. typhae also show that parasitism rates as high as 70% can occur, although this rates was observed only once, and the next closest value was half lower.…”

Tetrastischus howardi density and dispersal toward augmentation biological control of sugarcane borer

“…Most of the species within these genera develops through larvae and pupae partially protected inside host plant stalks, precluding control with contact insecticide sprayings (Pannuti et al 2013, Rossato Junior et al 2013. In contrast, biological control using larval-pupal parasitoids has been successful for this group of insects (Chichera et al 2012, Dinardo-Miranda et al 2014, Parra 2014, Vargas e t a l 2 0 1 5 ) . P a r t ic u l a r l y i n B r a z il , t he l a rv a l endoparasitoid Cotesia flavipes (Cameron) has been released in more than 35% of cultivated area with sugarcane to control Diatraea saccharalis (Fabr.)…”

“…and Diatraea flavipennella (Box.) (Silva et al 2012, Vacari et al 2012, Dinardo-Miranda et al 2014, Parra 2014.…”

Microsatellite loci and genetic structure of artificial populations of Cotesia flavipes (Hymenoptera, Braconidae)

“…This hypothesis is supported by the finding that the activity radius of C. flavipes in the field has been decreasing over the years. This radius was reported to be 34 meters in 1980 (Botelho et al, 1980), 25 meters in 2009 (Volpe, 2009) and 15 meters in 2014 (Dinardo-Miranda et al, 2014). On the other hand, in an initial introduction of C. flavipes in maize fields in Kenya, Africa, larvae parasitized by C. flavipes were found at a distance of 64 meters from the release point (Sallam et al, 2001).…”

“…A number of reports have described the biology and behavior of C. flavipes in Brazil (Campos-Farinha et al, 2000;Dinardo-Miranda et al, 2014;Volpe et al, 2014). Despite its economical importance and use in applied biological control, little is known about the genetic diversity of C. flavipes.…”