Field monitoring of BYDV risk in winter cereals (pilot study)
This project explored the potential to develop a field-based monitoring approach to help predict the risk of Barley yellow dwarf virus (BYDV) transmitted by cereal aphids in the autumn.
As part of a literature review, the project appraised BYDV decision support tools (DSTs). This identified two models and DSTs developed in the UK that could provide a basis for a new BYDV support service. However, the availability of the full documentation and/or code needs verifying and refining, especially with respect to a field monitoring system linked to yield loss estimates.
A survey of farmers and agronomists identified a high potential (92% of respondents) for adoption of a farm-based tool that integrates risk factors with current and refined practices, such as the use of weather data and monitoring at field and wider scales.
A field-specific monitoring method, based on yellow sticky traps mounted horizontally (just above the crop), was developed and evaluated. This aimed to determine: a) predictive capabilities of the method, b) practicalities of use by farmers and agronomists, c) whether landscape composition, boundary or tillage type affect immigration of aphid vectors. The sticky traps were effective at sampling winged cereal aphids. A 20 x 20 cm trap was sufficient to identify differences within and between fields. In a small plot trial, numbers of bird cherry-oat aphids caught on sticky traps was negatively related to yield. However, because of low plant colonisation, predictive capabilities, with respect to crop aphid infestation levels and BYDV, could not be tested. Trials of the sticky trap system by farmers and agronomists showed that aphid identification skills need improving. However, even with minimal training, people could detect aphid trends. All trial participants and 90% of survey respondents expressed willingness to monitor sticky traps on a weekly basis, on approximately four fields per farm. Across all studies, traps captured at least three times as many cereal aphids in the headland areas of fields, especially next to taller field boundaries. This indicates that wind currents determined aphid immigration patterns within fields. Such spatial pattern offers the opportunity to spray headland areas only to reduce insecticide usage. However, research needs to confirm the impact on whole field populations and BYDV infection, accommodate pesticide application restrictions and investigate the threat to boundary overwintering invertebrates. Considerable variation was found in levels of immigrating aphids between fields (24% of fields had no aphid immigration), even on the same farm. This confirms the merit of a field-based monitoring system to reduce insecticide usage. Landscape composition influenced levels of immigrating grain aphids, with grassland increasing levels. The type of tillage had no impact on levels of immigrating winged aphids. This shows that deposition was passive, determined by wind vortices, rather than by active selection during flight. Less than 5% of aphids were infected with BYDV.