No abstract

Runoff events in soybean growing areas of the Pampa s plains cause the mobilizatior of pesticides from agricultural fields into water bodies, contributing to invertebrate, fish and anuran kills (Natale and Ronco 2003; Jergents et al. 2004a; Carriquiriborde et al., personal communication). Cypermethrin, Chlorpyrifos and Endosulfan are commonly used insecticides in soybean crops of the region, though their concentratior levels in water and sediments of related surface water bodies has only recently beer characterized (Peruzzo et al, 2003; Jergents et al. 2004a-b;Marino et al. 2004).Taking into account that the extent ot the crops in the region is about ten million hectares of the genetically modified soybean variety (RR), the aim of the present study is to determine concentration levels of cypermetrin and chlorpyrifos in water and sediments from a first order stream of the Pergamino-Arrecifes system, and in the lower basins of five main tributaries flowing into the Parana river. MATERIALS AND METHODSThe study area took into consideration the assessment ot cypermethrin and chlorpyrifos concentrations at two scale levels of the Pampa Ondulada region. For a detailed scale study, a first order stream of the Pergamino-Arrecifes system was chosen (Figure 1) with its source within crop fields. The sampling campaigns during two consecutive years took into account the time for spraying of pesticides and the rain events immediately following sprays (table 1). Three sampling sites were selected to assess a direct influence of agricultural activity: Site 1, adjacent to field crops; Site 2 at 200 meters down stream, following the first site, adjacent to pasture, and Site 3 down stream next to a marshy sector, 500 meters from the first site. For the extended work scale, the assessment covered the lower basins of five rivers traversing crop field production areas. The water courses flow from the west to the east within the province of Buenos Aires, reaching the Parana river in its middle and low sectors (Manassero et al. 2005). Listed from north to south they are: del Medio stream, and Ramallo, Tala, Arrecifes and Areco rivers. All sampling sites and campaign details for the first order tributary are shown in figure 1 and table 1. Campaign sampling dates for the extended work scale are given in table 2.

No abstract

Eriopis connexa is a native coccinelid predator in the Neotropical Region. In Argentina it is commonly found associated to sucking pests in several crops and among them aphids and whiteflies. These pests are usually controlled with newly developed systemic insecticides, such as the neonicotinoids. However, the compatibility between selective pesticides and natural enemies is required before incorporating them in integrated pest management (IPM) packages. Within this frame, the objective of this study was to evaluate the side effect of various concentrations/doses of one commonly used neonicotinoid in vegetal crops, acetamiprid, on immature stages of E. connexa by dipping or topical exposure for eggs and larvae, respectively. Acetamiprid reduced egg hatching from 34 to 100 %. Moreover, the embryogenesis was disrupted by insecticide at early embryo stage at all tested concentrations. Second larval instar was more susceptible to acetamiprid than the fourth one and this susceptibility was positively related with the tested concentrations. On the other hand, the survival reduction at larval stage reached 100 % from 20 mg a.i./L (10 % of maximum field concentration). Besides, the reproduction of the females developed from topical bioassays on fourth instar larvae was strongly affected, with reduction in fecundity and fertility from 22 to 44 % and from 37 to 45 %, respectively. Overall the results showed a high toxicity of acetamiprid on immature stages of E. connexa, demonstrating that this broadly used insecticide could reduce biocontrol services provided by this predator and could also likely disturb IPM programs.