Planning T0 for 2021
The autumn of 2020 saw two main drilling windows; late September to early October, followed by late October – early November before the rain resumed. Disease risk will be differ between crops which were drilled a couple of weeks apart, this needs to be taken into account when designing T0 strategies. Early drillings will present a crop with higher septoria, eyespot and take-all risk, whereas late drilling are more prone to suffer from yellow rust. Following the later drillings, septoria risk will start to increase in response to April and May rainfall, therefore growers will need to keep vigilant as the season progresses and respond accordingly with T1 & T2 applications.
Varietal susceptibility will have an influence over fungicide programmes, helping to weigh in on the level of risk one can take when designing a fungicide sequence. Weather predictions in combination with AHDB disease scores for each variety can affect decisions as to the importance of using protectant chemistry over actives with some curative action. Elation (4.1), KWS Barrel, KWS Jackal, KWS Kerrin (4.2) and RGT gravity (4.8) all have a score under 5 for Septoria resistance, therefore will require a more robust fungicide approach to maintain yields. On the other end of the spectrum, Theodore (8.3), Extase (8.0) and LG Sundance (7.9) have higher resistance to septoria. Drilling date will affect the rating scores: anything drilled two weeks before 1st reduces the disease rating for septoria by one point or two points if drilled before 10th September.
The AHDB recommended list has seen some changes regarding yellow rust ratings since last season. The weakest contenders are Skyfall (3.0), KWS Kinetic & KWS Kerrin (4.0), KWS Zyatt, SY Insitor, Gleam, RGT Wolverine & Shabras (5.0). These varieties will need closer monitoring and quick action to ensure the rust does not take hold.
A good disease programme will take into account all the factors into account as well as cost to ensure a low selection pressure on the fungicide actives we have left. With CTL revoked, we have Folpet as a multisite which can act to prevent resistance when used in partnership with a single mode of action fungicide. Where septoria is a risk from late tillering to stem extension (T0), folpet can clear up an early infections and lessen further rain splash onto consequent leaves. Adequate nutrition at this time will also give the plant the best standing to respond to disease pressure and remain healthy. Established rust at the T0 timing can be treated with tebuconazole or cyproconazole. Bromuconazole and flutriafol will also give a level of control. For long lasting protection against rusts, azoxystrobin or pyraclastrobin should be used, also proving physiological benefits.
If you have any questions, or would like to discuss purchasing of crop protection products, please call 01243 755610 or email chems@bartholomews.co.uk