Rain and some warmer days in the second week of March have encouraged an explosion of yellow rust. Unsurprisingly, Oakley is the main culprit but numerous other varieties, especially in later drilled situations, are showing a lot of active yellow rust. Brown rust, mildew and septoria are also all easily found.
The combined effect is to trigger T0 fungicide treatments, in most cases utilising the eradicant benefits of products containing both triazole and morpholine. The addition of chlorothalonil has generally been avoided as it can reduce disease control in highly eradicant situations.
In all but the most forward crops the T0 timing is slightly prior to leaf 4 emergence. It will therefore be vital to consider intervals (max 3-4 weeks) when deciding on the T1 timing, so as not to let disease back into the crop. Where yellow rust is the biggest concern then T0 treatments are being made more robust to improve both eradication and persistence and try to carry crops through to T1.
The earlier drilled and faster developing varieties, in many cases, will have already received the first split of their PGR program. Again, robust treatments have been used in these higher lodging risk situations, with a view to following up with another robust treatment at T1.
Managing lodging also requires careful use of nitrogen and accurate knowledge of SMN levels under these crops. The more forward first wheats will start to have their first top dressing in the next week or two as they switch from vegetative to reproductive mode and stop producing additional tillers.
Oilseed rape is well into stem extension with most crops receiving a PGR-active fungicide to reduce final height, remove apical dominance, encourage side racemes and improve root mass.
Pollen beetle has been active in most rape fields, although cooler damp conditions have reduced their movement through crops. Again, this year, there is concern over pyrethroid resistance – especially in the Eastern counties – and some are switching to alternative modes of action to try to achieve better levels of control and greater product persistence. Further fungicide treatments will be required to protect the crop from disease during the flowering period and to maintain crop health.