One of the most important services provided by biodiversity is thought to be the biological control of pests in agricultural landscapes, including aphids on cereals. The food webs potentially contributing to biological control of aphids primarily consist of polyphagous predators, parasitoids and pathogens. The problems of aphid pests have increased greatly since the 1970-ies, possibly as an effect of agricultural intensification, which is thought to have reduced diversity and abundance of these predators and parasites and consequently their biocontrol potential. The main objective of this study was to test this by measuring this potential for biological control of aphids, and relate it to agricultural intensification and predator abundance. We selected 30 farms distributed along agricultural intensification gradients, based on the amount of fertilizers applied per hectare. Estimates of ground-living predator density were obtained using pitfall trapping over a one-week period. Traps were placed inside the cereal fields, 10 m from the margin, in 2 replicates per field. Predation risk due to ground-living predators (biocontrol potential) was estimated by monitoring removal of aphids glued to labels. This was done in the same fields, in the immediate vicinity of the traps, over a period of 2 days. The proportion of aphids eaten per unit time was the response variable. We present the correlations between intensity of agricultural exploitation, predator abundance and biocontrol potential. The outcomes are not straightforward in that intensification begets a reduction in predator density and biocontrol potential. We discuss the potential confounding issues that might have affected our results.
Ailinella gen. n. (Pseudophyllidea: Triaenophoridae) is proposed to accommodate Ailinella mirabilis sp. n. from Galaxias maculatus (Jenyns, 1842), a freshwater fish inhabiting the Andean lakes in Argentinean Patagonia. Ailinella belongs to the Triaenophoridae because it has a marginal genital pore, a follicular vitelline gland, and a ventral uterine pore. The new genus can be distinguished from other triaenophorids by the following combination of characters: a small body size, a low number of proglottides, which are longer than wide, a truncated pyramidal to globular scolex, a rectangular apical disc, presence of the neck, lack of internal longitudinal musculature separating the cortex from the medulla, testes distributed in one central field surrounding the ovary laterally and posteriorly, the vagina predominantly anterior to the cirrus sac, vitelline follicles circum-medullary, the genital pores post-equatorial, a saccate uterus, and operculate eggs. Blade-like spiniform microtriches were present on all tegument surfaces, and tumuli on all surfaces of the scolex and the anterior surface of the neck. Microtriches were characterized according to their size and density, and tumuli according to their size, inter-tumulus distance and density. Ailinella mirabilis is the first cestode described from G. maculatus and the second triaenophorid species recorded from a South American freshwater fish.