May 12, 2023
Cropwatch South – May 2023
After two relatively dry springs in a row, it’s easy to forget how much pressure Septoria can put on the system.
With 2012 firmly fixed in the memory, though, we know timeliness will be everything this season. So, alongside prioritising our highest risk wheats, we’re making sure we don’t miss any spraying opportunity, however slender.
In priority-setting, 2012 taught us that drilling date is far more important than genetics when the Septoria going gets tough.
All but our latest drilled wheats received folpet at T1 with some pretty weighty mixes of SDHIs, azoles and spiroxamine. This may have added £15/ha to the bill, but it’s a small price to pay in a total crop cost of over £1500; especially with the 4t/ha responses to decent fungicide programmes we saw in 2012.
The latest Septoria chemistry will certainly be earning its keep for its curative value. The fact that today’s fungicide formulations can be rainfast in an hour (on dry leaves) is another great advantage. Even so, it looks like we’ll need to take a few chances between showers to make sure our T2s are as timely as they need to be.
The cold-delayed start to our T0s and just enough late-April spray windows meant almost all our T1s went after no more than a three-week gap. And, with growth picking-up as we get some real warmth, we should have a good target for our flag leaf sprays before the next three-week interval is up.
These will be as curative as we can make them, with sufficient emphasis on rust and stem-based disease activity too. While rust infections have yet to become significant, they can emerge so rapidly with shifts in the weather. At the same time, there’s plenty of stem browning evident, and all three of this season’s most widely-grown varieties have eyespot resistance scores of less than 4.0.
Our pretty robust PGR programmes, including split applications of trinexepac at T0 and T1, have continued to pay dividends. And thick crops growing especially rapidly in plenty of moisture mean we may well be including the wide-application window chlormequat, Adjust plus ethephon at T2 on fertile or manured ground.
With some crops only just coming into full flower, our OSR is about two weeks behind where it usually is, so we’re only now starting in on the sclerotinia sprays.
Yellow bud-applied Architect (mepiquat-chloride + prohexadione-calcium + pyraclostrobin) has done a brilliant job promoting side branching as well as keeping light leaf spot in check.
Providing flowering proves relatively short as well as late, we’ll be following this up with single sclerotinia spray in most cases. As we are easily finding the threshold level of one seed weevil/plant in a number of crops, we will be including the pyrethroid, Mavrik (tau-fluvalinate) wherever necessary here.
Our February-drilled barleys continue to look very promising, and even our delayed April drillings are coming through well now. All the peas are in too, leaving only the maize still to be drilled.