Studies on Pseudapanteles dignus (Hymenoptera: Braconidae), a larval parasiotid of Tuta absoluta in Argentina

SALAS G. , NADIA G.

Ribeirao Preto

Simposio; 15° Simposio de Controle Biologico; 2017

SEB-UNESP-

There exist reports of a rich natural enemies complex for T. absoluta in Argentina that attacks the different developmental stages of this pest. Particularly for Argentina, knolwedge on the endoparasitoid Pseudapanteles dignus (Muesebeck) (Hymenoptera: Braconidae), a main species among the larval parasitoids of T. absoluta, points out a priori several positive biological characteristics to be considered as a BC agent. With the objective of expand knowledge about the spatiotemporal dynamics of P. dignus in Northeastern Buenos Aires province, an important horticultural region of Argentina, were performed monthly samplings, among the years 2013 and 2015, of gelechiids in cultivated and wild solanaceous species present in the CHP región. In addition, the mortality of T. absoluta in greenhouse tomato by means of different releasing rates of P. dignus, was estimated at experimental scale and several biological attributes (develpmental time, fecundity, longevity) and parasitism behavior (functional response) of P. dignus attacking T. absoluta in eggplant under laboratory conditions. Results showed that the interaction T. absoluta - P. dignus is part of a complex trophic web, conformed by cultivated and wild solanaceous species, T. absoluta and other gelechiids, and P. dignus and other larval parasitoids. Besides, the wild species N. glauca, S. americanum, and S. sisymbriifolium could help mantaining the interaction T. absoluta - P. dignus in eggplant and tomato crops. Further, it was evidenced that P. dignus exhibits a greater specificity towards T. absoluta, independently of the host plant it uses.The study of confined releases revealed that for a density of 10 hosts per plant, the release rate of 3 parasitoid females yielded a higher percentage of parasitism than greater rates, suggesting that the biocontrol of T. absoluta could be affected by mutua interference of numerous adult parasitoid females in the experimental unit. At lower host densities, release rates of 1 or 2 P. dignus wasps did not affect the percentages of parasitism reached, meanwhile at the lowest host density tested (2 larvae per plant) parasitism was not registered, an indication that host searching efficiency dimishes at smaller host densities. P. dignus developed slower (~ 5d), the female lived shorter (~ 2d), had a longer reproductive period (~ 4d), and a lower fecundity (estimated as the number of cocoons formed) when reared on T. absoluta fed on S. melongena plants than on S. lycopersicum. Functional response of P. dignus on eggplant was density-independent of the host density offered, as in tomato plant.To conclude, P. dignus can be considered a potentially effective biocontrol agent of T. absoluta for the BC of this pest in Argentina, based either by augmentative releases or by conservation strategiesin tomato and eggplant crops.