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There are many reasons why it is important that we find ways to conserve, and better utilize natural enemies of invertebrate crop pests. Currently, measures of natural enemy impact are rarely incorporated into studies that purport to examine pest control. Most studies examine pest and natural enemy presence and/or abundance and then qualitatively infer impact. While this provides useful data to address a range of ecological questions, a measure of impact is critical for guiding pest management decision-making. Often some very simple techniques can be used to obtain an estimate of natural enemy impact. We present examples of field-based studies that have used cages, barriers to restrict natural enemy or prey movement, direct observation of natural enemy attack, and sentinel prey items to estimate mortality. The measure of natural enemy impact used in each study needs to be tailored to the needs of farmers and the specific pest problems they face. For example, the magnitude of mortality attributed to natural enemies may be less important than the timing and consistency of that mortality between seasons. Tailoring impact assessments will lead to research outcomes that do not simply provide general information about how to conserve natural enemies, but how to use these natural enemies as an integral part of decision-making.

The modern Arctic Ocean is regarded as barometer of global change and amplifier of global warming 1 and therefore records of past Arctic change are of a premium for palaeoclimate reconstruction. Little is known of the state of the Arctic Ocean in the greenhouse period of the late Cretaceous, yet records from such times may yield important clues to its future behaviour given current global warming trends. Here we present the first seasonally resolved sedimentary record from the Cretaceous from the Alpha Ridge of the Arctic Ocean. This "paleo-sediment trap" provides new insights into the workings of the Cretaceous marine biological carbon pump. Seasonal primary production was dominated by diatom algae but was not related to upwelling as previously hypothesised 2 . Rather, production occurred within a stratified water column, involving specially adapted species in blooms resembling those of the modern North Pacific Subtropical Gyre 3 , or those indicated for the Mediterranean sapropels 4 . With elevated CO 2 levels and warming currently driving increased stratification in the global ocean 5 this stratified-adapted style of production may become more widespread.Our evidence for seasonal diatom production and flux testify to an ice free summer, but thin accumulations of terrigenous sediment within the diatom ooze are consistent with the presence of intermittent sea ice in the winter, supporting a wide body of evidence for low Arctic late Cretaceous winter temperatures 6-8 rather than recent suggestions of a 15°C mean annual temperature at this time 9 . 3The Arctic is a critical yet under-sampled region for palaeoclimate studies. The recent ACEX coring has provided Arctic records back to the Palaeogene 10 but earlier shallow coring of older, Cretaceous sediments has hitherto offered only tantalising indications of the Arctic palaeoenvironment 2,9,11,12 . Such sediments afford the opportunity to investigate Arctic climate variability in past greenhouse states that may be analogues for the future. Specifically, little is known of Arctic seasonal-scale climate variability in periods without permanent sea ice cover. Cretaceous laminated sediments also provide a "palaeo-sediment trap" record whereby the past workings of the marine biological carbon pump may be elucidated. In the modern ocean diatom algae are responsible for up to 40% of oceanic primary production and because they dominate export in many marine environments, diatoms are the key agents in the marine biological carbon pump, central to biogeochemical cycling 13,14 . By contrast, the role of diatoms in the Cretaceous oceans is poorly understood, in part, due to lack of preservation, since opal A is unstable and diatoms are easily destroyed during sediment burial and silica diagenesis. However, the first, albeit rare, pelagic diatomites occur in the late Cretaceous coinciding with a radiation of planktonic diatoms 15 , and in late Cretaceous sediments without surviving biosilica, there is increasing biomarker evidence of diatom contribution to carbon cyc...

Earth's climate transitioned from a warm unglaciated state to a colder glaciated "icehouse" state during the Cenozoic. Extensive ice sheets were first sustained on Antarctica at the Eocene-Oligocene Transition (EOT,~34 Ma), but there is intense debate over whether Northern Hemisphere ice sheets developed simultaneously at this time or tens of millions of years later. Here we report on EOT-age sediments that contain detrital sand from Integrated Ocean Drilling Program Sites U1406 and U1411 on the Newfoundland margin. These sites are ideally located to test competing hypotheses of the extent of Arctic glaciation, being situated in the North Atlantic's "iceberg alley" where icebergs, calved from both the Greenland Ice Sheet today, and the Laurentide Ice Sheet during the Pleistocene, are concentrated by the Labrador Current and deposit continentally derived detritus. Here we show that detrital sand grains present in these EOT-aged sediments from the Newfoundland margin, initially interpreted to represent ice rafting, were sourced from the midlatitudes of North America. We find that these grains were transported to the western North Atlantic by fluvial and downslope processes, not icebergs, and were subsequently reworked and deposited by deep-water contour currents on the Newfoundland margin. Our findings are inconsistent with the presence of extensive ice sheets on southern and western Greenland and the northeastern Canadian Arctic. This contradicts extensive bipolar glaciation at the EOT. The unipolar icehouse arose because of contrasting latitudinal continental configurations at the poles, requiring more intense Cenozoic climatic deterioration to trigger extensive Northern Hemisphere glaciation.

Trichogramma Westwood (Hymenoptera: Trichogrammatidae) cause high mortality rates in the potentially resistant pest species, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), and are considered integral to the resistance management plan for Bacillus thuringiensis transgenic cotton, Gossypium hirsutum L., production in the Ord River Irrigation Area (ORIA), Western Australia. Measured as percentage of parasitism, Trichogramma activity seems highly variable over time; yet, it contributes significantly to pest suppression at peak insect pest density. Environmental constraints on Trichogramma survival, especially insecticide applications, may limit their effectiveness. The decision to initiate insecticide applications in ORIA cotton crops is best delayed unless absolutely necessary to avoid disruption of Trichogramma impact on pests. Trichogramma disperse into young crops and display high intrinsic rates of increase effectively stifling Helicoverpa (Hardwick) population increase after initial egg lay during high-density years in the ORIA, and evidence suggests a possible preference for H. armigera host eggs.

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Many farmers rely on regular pesticide applications to avoid losses from arthropod pests and the diseases they vector. However, widespread and injudicious use of pesticides is detrimental to the environment, poses a health risk, and undermines biocontrol services. Researchers are increasingly required to develop techniques to quantify the trade-offs and risks associated with pesticides. Laboratory studies, though useful for assessing short-term impacts (e.g., mortality), cannot detect longer-term or indirect effects that can potentially be assessed using semifield studies. Here we review the range and scope of studies that have used semifield methods for regulatory testing and risk assessment of pesticides and for understanding the community-level effects of pesticide use in agricultural landscapes. We include studies on target and nontarget species, with an emphasis on quantifying effects when the target species is highly mobile. We suggest improvements in the design and analysis of semifield studies to more effectively assess effects on highly mobile species.

1 Understanding the spatio-temporal dynamics of insects in agroecosystems is crucial when developing effective management strategies that emphasize the biological control of pests. 2 Wild populations of Trichogramma Westwood egg parasitoids are utilized for the biological suppression of the potentially resistant pest species Helicoverpa armigera (Hübner) in Bt-transgenic cotton Gossypium hirsutum L. crops in the Ord River Irrigation Area (ORIA), Western Australia, Australia. 3 Extensive, spatially-stratified sampling during a season of relatively high Trichogramma abundance found that spatial patterns of pest egg parasitism in the ORIA tend toward heterogeneity, and do not necessarily coincide with host spatiotemporal dynamics. Both patterns of host egg density and mean rates of parasitism are not good indicators of parasitoid spatio-temporal dynamics in ORIA cotton crops. 4 Parasitism rates can be significantly higher within the middle strata of the cotton plant canopy before complete canopy closure, despite a similar number of host eggs being available elsewhere in the plant. 5 Spatial variation in egg parasitism by Trichogramma in Bt-transgenic cotton is evident at the between-field, within-field and within-plant scale, and is not solely driven by host spatial dynamics. These factors should be considered when estimating Trichogramma impact on pest species during biological control and spatio-temporal studies of host-parasitoid interactions in general.