SignificanceDecades of research have fostered the now-prevalent assumption that noncrop habitat facilitates better pest suppression by providing shelter and food resources to the predators and parasitoids of crop pests. Based on our analysis of the largest pest-control database of its kind, noncrop habitat surrounding farm fields does affect multiple dimensions of pest control, but the actual responses of pests and enemies are highly variable across geographies and cropping systems. Because noncrop habitat often does not enhance biological control, more information about local farming contexts is needed before habitat conservation can be recommended as a viable pest-suppression strategy. Consequently, when pest control does not benefit from noncrop vegetation, farms will need to be carefully comanaged for competing conservation and production objectives.

Human land use threatens global biodiversity and compromises multiple ecosystem functions critical to food production. Whether crop yield–related ecosystem services can be maintained by a few dominant species or rely on high richness remains unclear. Using a global database from 89 studies (with 1475 locations), we partition the relative importance of species richness, abundance, and dominance for pollination; biological pest control; and final yields in the context of ongoing land-use change. Pollinator and enemy richness directly supported ecosystem services in addition to and independent of abundance and dominance. Up to 50% of the negative effects of landscape simplification on ecosystem services was due to richness losses of service-providing organisms, with negative consequences for crop yields. Maintaining the biodiversity of ecosystem service providers is therefore vital to sustain the flow of key agroecosystem benefits to society.

79 40 INRA, UR 1115, Plantes et Systèmes de culture horticoles, ABSTRACT 138

Liriomyza huidobrensis (Blanchard) is native to South America but has expanded its range and invaded many regions of the world, primarily on flowers and to a lesser extent on horticultural product shipments. As a result of initial invasion into an area, damage caused is usually significant but not necessarily sustained. Currently, it is an economic pest in selected native and invaded regions of the world. Adults cause damage by puncturing abaxial and adaxial leaf surfaces for feeding and egg laying sites. Larvae mine the leaf parenchyma tissues which can lead to leaves drying and wilting. We have recorded 365 host plant species from 49 families and more than 106 parasitoid species. In a subset of the Argentinian data, we found that parasitoid community composition attacking L. huidobrensis differs significantly in cultivated and uncultivated plants. No such effect was found at the world level, probably due to differences in collection methods in the different references. We review the existing knowledge as a means of setting the context for new and unpublished data. The main objective is to provide an update of widely dispersed and until now unpublished data, evaluate dispersion of the leafminer and management strategies in different regions of the world, and highlight the need to consider the possible effects of climate change on further regional invasions or expansions.

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Abstract. 1. Sugar from nectar or from honeydew can prolong parasitoids' lifespan, enhance their fecundity and foraging ability, and thereby increase their pest suppression efficiency. Sugar sources within crop monocultures are considered to be limiting for parasitoids. Nevertheless, only few studies have measured the sugar feeding of parasitoid assemblages in agricultural areas or in surrounding non-crop habitats.2. We used cold anthrone tests to compare the frequency of sugar feeding in parasitoid communities, inside pomegranate orchards and in adjacent natural areas, over two consecutive years. Overall, 40% of the 1610 sampled individuals belonging to 135 species scored positive for sugar.3. Sugar-feeding frequency was lower within the orchards than in the neighbouring natural areas. The proportion of sugar-fed wasps increased with herbaceous vegetation cover, both within and outside the orchards, suggesting that herbs are a sugar-rich habitat. Parasitoids sampled from trees and from herbs within the orchards had similar frequencies of sugar feeding, despite differences in wasp species composition.4. Our results probably overestimate sugar-feeding frequencies in the field because sugar-fed individuals have higher longevity and hence are more likely to be sampled. We propose a simple model to approximate this over-sampling bias and apply it to Encarsia inaron (Aphelinidae), one of the most abundant parasitoids in the samples.5. We conclude that sugar availability potentially limits parasitoid fitness in this agro-ecosystem. This may be due to the low density of plants in natural areas during the Mediterranean summer, and to herbicide applications within the orchards that further suppress non-crop herbs.

Parasitoids that encounter a previously parasitized host inspect it externally and internally, sometimes eventually laying additional eggs (superparasitism). The fitness effects of increased clutch sizes generated through superparasitism are widely studied, whereas the consequences of multiple host probings during the inspection received less attention. To address this issue, we offered a host to 1-5 females of the encyrtid wasp Copidosoma koehleri consecutively, or presented it 1-5 times to a single female. We noted whether the hosts died before pupation of either host or wasp, produced parasitoid pupae, or developed into moth pupae. Additional hosts were dissected after varying numbers of probings to determine their parasitoid egg loads. Host rejection rates prior to ovipositor insertion did not differ between treatments. Host rejections after ovipositor insertion, characterized by brief (<10 s) probing durations, were more common in the single-than in the multiple-female treatment. This could reflect avoidance of self-superparasitism, or increased selectivity by host-experienced females. Egg number per host increased with the number of prolonged probings in both treatments. Some hosts that received 1-2 probings (brief or prolonged) yielded moth pupae, while no hosts with five probings survived to pupation. Hosts probed three times (corresponding to <1 and 2.2 eggs in the single-and multiple-female treatments, respectively) produced the largest proportion of parasitoid pupae. The parasitoids' success is thus strongly affected by the number of host probings. Overcoming host defenses through repeated probings is a previously overlooked potential benefit of superparasitism.

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