Crops and Soils Bulletin June 2023 – Barley Yellow Dwarf Virus: Symptoms and IPM Management
20 June 2023
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Dry conditions and high temperatures of 25°c plus this month are leading to/increasing plants under stress which are more susceptible to barley yellow dwarf virus due to lower reserves of soluble stem carbohydrates. Direct feeding of aphids should be monitored closely until harvest. Symptoms seen include discolouration of the leaves; barley turns golden-yellow, oats turn purple-red and wheat turn yellow (image 1). All infected plants will experience premature senescence; however winter barley is less susceptible due its natural early senescence.
Infected plants on average store up to three times more starch in the leaves causing a decrease in chlorophyll concentration. Chlorophyll is used by plants to obtain nutrients and gives plants their green colour, therefore with a reduction in chlorophyll there is less green mass which hinders photosynthesis, declining the health of the plant. BYDV affects plant physiology subject to the growth stage of the plant when infected by the aphid and the extremity of the infection. If crops are infected in the later growth stage of flowering a reduction in the number and size of grain produced will occur (Charles-Antoine Dedryver, 2010).
Data provided by Rothamsted Insect Survey offers a text message service alerting aphid activity from the suction-trap network based in Inverness, Dundee, Gogarbank, Ayr and Newcastle giving regional indication of infestation numbers. Combining this with using yellow sticky traps (image 2) in the fields to give site specific field indications will allow better judgement for best timing of control applications.
Sole chemical dependence on Pyrethroids has seen widespread resistance in the grain aphid and concerns continue with potential resistance establishing in the bird cherry-oat aphid. With prevailing resistance developing in aphids it is vital to not overlook non-chemical control. Relying on active ingredients with no integrated cultural or biological control will continue to see increased resistance and less control distinguished (figure 1).
Biopesticides are commonly used in organic systems and vegetable production but are becoming more of an interest on cereal aphids due to the loss of active chemicals and can potentially be a durable control alternative whilst promoting sustainable crop protection (Louise Mc Namara, 2020). In laboratory environments various plant compounds have shown success in managing cereal aphids, specifically in impeding the pre-reproductive stage of the grain aphid which resulted in a reduction in population by 35-40% (Grzegorz Chrzanowski, 2012). However, reports showed a weakness in research at field scale. At field scale essential oil blends of cumin, hyssop, costmary, lavender and thyme have proved to deter the bird cherry-oat aphid from barley and wheat crops (Daniela Gruľová, 2017) and neem seed oil specifically lowering the grain aphid infestations in Pakistan (Farhan Mahmood Shah, 2017).
Forward thinking to next years’ crop consider later sowing dates, encouraging natural enemies and using wheat variety RGT Wolverine, resistant to BYDV, and the barley variety KWS Feeris, tolerant to BYDV. Trials using Feeris showed a 21-23% yield increase (AHDB, 2022). Adopting an IPM approach will aid to extend efficacy of active ingredients, reduce pesticide residuals and steady the evolution of resistance.
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