ABSTRACT
Large scale mass rearing of natural enemies has been a mean of improving biological control in the sugarcane intensive agriculture. Among them, Cotesia flavipes, a gregarious koinobiont endoparasitoid, was imported by Brasil to control caterpillars of the sugarcane borer Diatraea saccharalis. The C. flavipes larval development depends on its association with polydnavirus, which blocks the host defense reaction. To verify if the oviposition sequence (1st, 2nd or 3rd) and the female condition (mated or virgin) interfere in the number of C. flavipes descendents, 4th instar caterpillars of D. saccharalis were parasitized. Analysis of the data showed that: a) there is an inverse correlation between the parasitism efficiency and the host reaction (encapsulation); b) the number of caterpillars parasitized by virgin females that released parasitoid larvae in the period from 12 to 15 days was higher than that of caterpillars parasitized by mated females; c) a slight difference between mated and virgin females in relation to the parasitim success was observed; and d) the number of encapsulated parasitoid larvae was higher than that of eggs, suggesting that eggs have a better capacity to overcome the host reaction. In this study, the viability of C. flavipes eggs and larvae in the non-specific host D. saccharalis could be correlated with the oviposition sequence and the female condition
Subject(s)
Animals , Male , Female , Parasitic Diseases , Parasites/growth & development , Agricultural Pests , Insecta/parasitologyABSTRACT
The main objective of this study was a bio-economic survey of artisanal fishing so as to compare average profit of the fishermen, in two different environments (reservoirs and river) and seasons (dry and rainy). To carry out financial comparisons of artisanal fisheries in Urubupungá Complex in the middle Paraná River (Brazil), three habitats were considered: I) Ilha Solteira and Jupiá reservoirs; II) the Paraná River between the Jupiá and Primavera dams; III) the Paraná River downstream from the Primavera dam. Data collection was done through questionnaires addressed to a total of 187 fishersmen; just 164 of the resulting interviews were considered valid. They were held in July 1998 (dry season) and February 1999 (rainy season). The daily average profit of the resevoir fisherman was R$ 13.19 during the dry and R$ 19.54 during the rainy season; R$ 4.10 and R$ 12.92 for fishermen located on the Paraná River between Jupiá and Primavera dam; and R$ 1.48 and R$ 23.01 for those located on the Paraná River below Primavera dam (R$ 1.00 = US$ 0.86 during the dry season; R$ 1.00 = US$ 0.52 during the rainy season). A linear model had been tried to explain the profit variable, in relation to those variables directly linked to fishing (e.g., as habitats; seasons, dry or rainy; gear used; days spent fishing) as well as several sociological variables (age, marital states, number of dependents, and education). However, due to large variability in profits, the proposed model only explained 48.4 percent of variability, and the only significant factors were education, type of gear, and covariant fishing days.