Interspecific competence between the ectoparasitoid Dineulophus phtorimaeae de Santis (Hymenoptera:Eulophidae) and the endoparasitoid Pseudapanteles dignus (Muesebeck) (Hymenoptera:Braconidae), attacking Tuta absoluta larvae in the laboratory

The idiobiont ectoparasitoid Dineulophus phtorimaeae and the koinobiont endoparasitoid Pseudapanteles dignus are main native larval parasitoids of Tuta absoluta in tomato crops in Argentina. Since their host niches are partially overlapping, they could hypothetically compete for hosts, and a priori, theory predicts that idiobiont are competitively superior to koinobiont parasitoids. Moreover, the condition of individual parasitoid females, such as age, sources of food, etc., could influence the ovipositing behavior, leading to multiparasitism. The objective of this study was to elucidate aspects of competence between D. phtorimaeae and P. dignus in the laboratory. Through a choice test, D. phtorimaeae adult females were offered to 6-8 T. absoluta larvae for a 48 h-period. Two factors were considered (n= 15 per treatment): 1) healthy or P. dignus parasitized hosts, and 2) three D. phtorimaeae adult wasps’ ages. After the experiment was terminated, all T. absoluta larvae were revised for signs of paralization (host-feeding) or the presence of eggs/larvae of D. phtorimaeae, and later dissected to search for P. dignus immatures (healthy or paralyzed by the ectoparasitoid). Two-way ANOVA showed that D. phtorimaeae female´s age and also the concurrent interaction effect of age * P. dignus parasitized/non parastized hosts led to significantly differences in the proportion of multiparasitized T. absoluta larvae. Thus, younger D. phtorimaeae females avoided to attack on T. absoluta larvae previously parasitized by its competitor, P. dignus; meanwhile older ones could not help using parasitized hosts, and consequently succeeding over the endoparasitoid.