Cereal crops were held back by the cold temperatures of late April and early May and are now leaping through growth stages to catch up. In wheat crops the final sprays to be applied will be the ear sprays which are ideally targeted at early to mid flowering to maximise the chances of getting good control of ear diseases such as fusarium and microdochium which can be detrimental to yield and grain quality, with fusariums also posing a risk of mycotoxins being present in the crop. This timing is also important to ‘top up’ foliar disease protection as keeping upper leaves green for as long as possible is very important to final yield. The best late sprays on wheat are therefore those that give good control of ear diseases combined with good control of septoria. Tebuconazole for example is very good at the former but not so good at the latter. Prothioconazole is particularly active against fusariums and microdochium and is also one of the top two azoles for septoria control. Azole mixes also have a good fit at this timing. SRUC trials consistently show an advantage of including chlorothalonil at this timing. Pay careful attention to the latest timings of applications and also to any label restrictions on the number of applications you can make of any products.
In barley crops the late spray is targeted at ramularia protection and also as a top up of earlier protection against rhynchosporium, net blotch and mildew. In winter barley the biggest yield response usually comes from the early spray timing at the start of stem extension but in spring barley it is usually more evenly split with very large responses seen in years where there is a lot of ramularia. In SRUC trials the SDHI fungicides have particular activity against ramularia so are a good fit here. Prothioconazole is the most active azole fungicide against all the barley diseases so azole + SDHI mixes (plus or minus chlorothalonil depending on disease risk) consistently do well in our trials. The best timing for this spray in barley is booting to early ear emergence – be very careful of latest application timings as for some products awns peeping is the cut off.
In both wheat and barley over recent wet summers there have been concerns about sooty moulds and late ear infections. SRUC carried out a series of field trials funded by the Loirston Trust over three seasons and we consistently saw no additional benefit to late and additional ear sprays once crops were in the ripening growth stages. Sooty moulds, although visually unattractive, are not that damaging to yield and because the ear diseases that are damaging to yield, such as Fusarium and Microdochium, usually infect at early flowering there is little benefit to a late spray when it is already established. In barley there is some scope to push the booting spray out to early ear emergence but that depends on the product being approved for that timing and an ability to move very fast to apply it as this leaves no margin of error as most effective products cannot be applied to the flowering crop. Booting therefore remains the best compromise timing in barley.
Fiona Burnett, Crop & Soil Systems, SRUC.
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