East: Monitor wheats for yellow rust

Wheels have been turning during the last fortnight as drier weather has allowed good conditions for spring drilling and pre-emergence sprays. Many sugar beet crops were drilled during the second and third weeks of March and are now close to emergence.

Warming temperatures and recently applied nitrogen have accelerated crop growth, whilst increasing day length drives crop development forward.All wheat varieties are showing septoria lesions on their lower leaves. While septoria remains the dominant disease, our attention has been drawn to yellow rust, which is now widespread in the eastern counties on cultivars Oakley and Robigus.The NIAB Variety Diversification Scheme to Reduce Spread of Yellow Rust in Wheat, 2011, shows which varieties are susceptible to the same race of this pathogen.  Other varieties within the same “Diversity Group” to Oakley and Robigus are also at high risk of infection and should be monitored carefully as many of these, such as Viscount and Solstice, also have low resistance ratings for yellow rust.

T0 fungicide sprays and early plant growth regulator applications (PGRs) have begun on early September-sown wheats as these crops have reached the beginning of stem extension. 

Later-drilled crops at high risk from yellow rust, according to location and disease resistance, should also be protected from this disease – even if this means adjusting the traditional T0 timing, usually three weeks from T1, emergence of leaf 3. 

The early occurrence of yellow rust will also encourage more use of strobulurins at T1, especially if followed by the new SDHI fungicide chemistry at flag leaf. In these conditions, crops should be monitored carefully and spray timings should be kept tight with three to three-and-a-half weeks between sprays.

Forward oilseed rape crops and higher-biomass varieties such as Sesame should receive a plant growth regulator at green bud. Consider the pollen beetle strategy; populations across East Anglia now include beetles that are highly resistant to pyrethroids. Newer “non pyrethroid” options  such as thiacloprid (Biscaya), pymetrozine (Plenum) and indoxacarb  (Rumo) can be applied. Check individual labels for the latest timing of applications.

Winter barley T1 fungicides and early plant growth regulator treatments should be applied at early stem extension. Spring herbicide control in barley should be completed before the crop meets in the row and shades the target weeds.

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