Prospects for improved off-crop habitat management for pollen beetle control in oilseed rape

There is an urgent need to develop sustainable and environmentally benign integrated pest management (IPM) strategies for arable crops. The enhancement and manipulation of naturally-occurring populations of the natural enemies of crop pests through habitat management for ‘conservation biological control’, as well as habitat management to manipulate populations of the pests themselves, have the potential to become major components of successful IPM strategies. We review the studies that have contributed to our current understanding of how the crop margin, local landscape, and regional landscape can influence pollen beetle Brassicogethes aeneus (syn. Meligethes aeneus) (Coleoptera: Nitidulidae) abundance and damage to oilseed rape crops (Brassica napus), and the efficacy of their natural enemies. We also discuss how habitat management across these multiple scales may improve pollen beetle control, reducing the need for insecticide use and contributing towards sustainable production of this important crop which is grown on increasing areas for both food and fuel

The potential of crop management practices to reduce pollen beetle damage in oilseed rape

A major problem associated with agricultural intensifcation over recent decades has been the development of insecticide resistance in crop pest populations. This has been a particular issue for control of the pollen beetle (Brassicogethes aeneus syn. Meligethes aeneus), a major pest of oilseed rape throughout Europe. Sustained and often prophylactic use of pyrethroid insecticides has led to the development of insecticide-resistant beetle populations, and alternatively, more environmentally benign integrated pest management strategies are sought for the pest. The population dynamics of pollen beetles and their natural enemies, and the damage caused by the pest, are infuenced by processes acting at multiple scales,from the regional or landscape scale down to the local field or within-field scale. In this review, we focus on the within-field scale, and how crop management factors, including tillage,crop plant density, crop nutrition and crop rotations may be optimised and incorporated into integrated pest management strategies for more sustainable and effective control of the pes

Banker Plant Bonuses? The Benefits and Risks of Including Brassicas in Field Margins to Promote Conservation Biocontrol of Specialist Pests in Oilseed Rape

European agri-environment schemes include the use of flower-rich field margins to promote on-farm biodiversity, but species mixtures rarely include Brassicaceae. As pests of oilseed rape (OSR; Brassica napus) and their parasitoids are mostly brassica specialists, including brassica ‘banker plants’ in the mixtures would help support these important biocontrol agents and improve pest control throughout the crop rotation. We assessed the potential of six brassicaceous plants (replicated plots grown in the field) to enhance populations of parasitoids of OSR pests whilst minimising proliferation of their pest hosts. Fodder radish (Raphanus sativus) facilitated high production of parasitoids of the pollen beetle pest (Brassicogethes aeneus) but may proliferate Ceutorhynchus weevil pests due to low parasitism. Turnip rape (B. rapa) and the B. rapa hybrid ‘Tyfon’ showed potential to perform a trap cropping function for pests, but their early flowering phenology resulted in B. aeneus larvae escaping parasitisation, potentially assisting proliferation of this pest. Forage rape B. napus exhibited similarly high B. aeneus parasitoid production characteristics to R. sativus but did not potentiate problems with other pests, indicating that it would be a favourable banker plant option. Careful selection of plants in field margin mixtures is therefore needed to maximise their benefits and ideally the whole crop pest-beneficial complex needs to be studied, as focus on a single major pest risks unintended consequences with other pest problem

Meteorological and landscape influences on pollen beetle immigration into oilseed rape crops

Heavy reliance on pesticide inputs to maintain crop yields has been an important aspect of agricultural intensification. Insecticide use has had detrimental impacts on pollinators and natural pest control agents, contributing to a decline in associated ecosystem services, and has also led to resistance development in pest populations. Throughout Europe, in oilseed rape (Brassica napus L.) crops, prophylactic use of insecticides against pollen beetles (Meligethes aeneus F. also known as Brassicogethes aeneus) has led to such issues, and there is an urgent need to develop more sustainable pest management practices for the crop. Although advice is available to oilseed rape growers regarding control thresholds, it may not be adhered to due to the expense of pollen beetle monitoring relative to the inexpensive cost of pyrethroid insecticides. Thus, the key to reducing prophylactic insecticide applications may lie with improved, less labour intensive methods of pollen beetle monitoring. For these to be realized, a better understanding is needed of the effects of agri-landscape features and meteorological conditions on pollen beetle immigration into the crop. In this study, based on data from four years of pollen beetle monitoring on a total of 41 field sites, we model the effects of meteorological (wind speed and direction, rainfall and accumulated temperature) and landscape (areas of woodland, residential gardens, the current and previous seasons’ oilseed rape crops, and lengths of hedgerows and treelines) variables on directional sticky trap catches, at both the single trap and field scales. Meteorological variables, particularly accumulated temperature and wind speed were more important than landscape variables in predicting the abundance of pollen beetles immigrating into OSR fields. Sticky traps that were facing downwind caught more beetles than those that were facing across-wind or upwind; this is the first study to show at a landscape-scale, direct evidence for use of upwind anemotaxis by pollen beetles at the point of entry during immigration into the crop. At the field scale, the area of oilseed rape grown in the previous season was found to be positively related to trap catch, but no relationships with other landscape variables were found. Optimally-placed monitoring traps could complement existing decision support systems to reduce pollen beetle monitoring effort and encourage use of insecticides only when control thresholds are breached, thus enhancing the sustainability of oilseed rape production. Knowledge of the area of oilseed rape crops grown during the previous season in the surrounding landscape could contribute to risk assessment of potential pest pressure for individual OSR crops

The potential of decision support systems to improve risk assessment for pollen beetle management in winter oilseed rape

BACKGROUNDThe reliance on and extensive use of pyrethroid insecticides have led to pyrethroid resistance in pollen beetle (Meligethes aeneus). Widespread adoption of best practice in pollen beetle management is therefore needed. Decision support systems (DSSs) that identify the risk period(s) for pest migration can help to target monitoring and control efforts, but they must be accurate and labour efficient to gain the support of growers. Weather data and the phenology of pollen beetles in 44 winter oilseed rape crops across England over 4 years were used to compare the performance of two risk management tools: the DSS proPlant expert, which predicts migration risk according to a phenological model and local weather data, and rule-based advice', which depends on crop growth stage and a temperature threshold. RESULTSBoth risk management tools were effective in prompting monitoring that would detect breaches of various control thresholds. However, the DSS more accurately predicted migration start and advised significantly fewer days of migration risk, consultation days and monitoring than did rule-based advice. CONCLUSIONThe proPlant expert DSS reliably models pollen beetle phenology. Use of such a DSS can focus monitoring effort to when it is most needed, facilitate the practical use of thresholds and help to prevent unnecessary insecticide applications and the development of insecticide resistance. (c) 2015 Rothamsted Research Ltd. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry

Development of an integrated pest management strategy for control of pollen beetles in winter oilseed rape (HGCA Project Report No 504)

We have developed an integrated pest management strategy (IPM) for pollen beetles in winter oilseed rape (OSR) based on risk assessment, monitoring and alternative crop management that can be used as a framework by growers and crop consultants to manage pollen beetles with reduced insecticide inputs - and the confidence to do so. This will prolong insecticide life by reducing selection for resistance, reduce environmental impacts and contribute towards the sustainability and profitability of OSR in the UK. One of the major limitations to the use of action thresholds is that proper monitoring of the populations is time consuming and has to be conducted over a prolonged period. To encourage and facilitate their use, we tested and developed tools to improve risk assessment and monitoring. We conducted a pollen beetle monitoring study over 4 years in 178 OSR crops across the UK. Pollen beetles were sampled using sticky traps and plant sampling along transects in the crop. The data were used to help test a decision support system (DSS) for pollen beetles and to develop a monitoring trap. proPlant Expert is a DSS available in mainland Europe that uses a model of pollen beetle immigration and local meteorological data to forecast the start and end of pollen beetle immigration into the crop and main risk periods and advises when to monitor. We tested the model under UK conditions using data from our study and compared monitoring advice with the current advice system on the CropMonitor website (advises monitoring when the crop is at green-yellow bud stage and temperature >15°C). Both performed reassuringly well in prompting monitoring that would detect breaches of spray thresholds. However there were considerable reductions provided by proPlant in the need for consultation of the system (30%) and advised monitoring days (34-53%) in comparison with current advice. Use of the proPlant DSS could therefore focus monitoring effort to when it is most needed. It could also help to reduce unnecessary sprays in cases where beetle numbers are approaching threshold but consultation of the system returns a poor immigration risk forecast or an immigration complete result. The proPlant tool is now freely available to growers and crop consultants in the UK via the Bayer CropScience website. A monitoring trap for pollen beetles would help to more easily and accurately identify when spray thresholds have been breached than monitoring plants in the crop. We developed a baited monitoring trap for pollen beetles which will be commercially available from Oecos. The trap comprises a yellow sticky card mounted at 45°, baited with phenylacetaldehyde, a floral volatile produced naturally by several plant species. Unfortunately using data from our study we were unable to calibrate the trap catch to a given action threshold expressed as the number of beetles per plant using a simple linear relationship. However, the monitoring trap still has value for risk assessment, especially if used together with DSS. We tested the potential of turnip rape (TR) trap crops, planted as borders to the main OSR crop to reduce pollen beetle numbers in a field scale experiment conducted over three years on two sites. We found evidence that the strategy worked well in some years, but not others. This tactic is probably practically and economically worthwhile only for organic growers

Semiochemical-based alternatives to synthetic toxicant insecticides for pollen beetle management

There is an urgent need to develop sustainable pest management systems to protect arable crops in order to replace the current over-reliance on synthetic insecticides. Semiochemicals are insect- or plant-derived chemicals that are used by organisms as information signals. Integrated pest management tools are currently in development that utilise semiochemicals to manipulate the behaviour of pest insects and their natural enemies to provide effective control of pests within the crop. These innovative tools usually require fewer inputs and can involve multiple elements therefore reducing the likelihood of resistance developing compared with use of synthetic toxicants. We review here the life cycle of the pollen beetle Brassicogethes aeneus (previously known as Meligethes aeneus) which is a pest insect of oilseed rape (Brassica napus) and describe the current knowledge of any behaviour mediated by semiochemicals in this species. We discuss the behavioural processes where semiochemical-based control approaches may be appropriate and consider how these approaches could be integrated into an integrated pest management strategy for this important arable crop