Thursday, August 22, 2019

Busy month for combinable crop management

May 1, 2019 by  
Filed under Crops

A cold spell in mid-April slowed winter wheat development but T1 fungicides were still due before the month end, says Richard Overthrow.

Some late sown or late developing crops may still be waiting for sufficient Leaf 3 emergence but most crops will be waiting for flag leaf timing – with hopefully few needing an intermediate (Leaf 2) treatment.

Dry weather over March and April helped suppress Septoria but yellow rust was evident in a number of varieties but suitable treatment at T1 should have this under control now.

Flag leaf emergence in wheat is less affected by environmental conditions and is likely to be close to the normal date for your farm. Fungicide treatment should be fairly robust even if the preceding spray interval was short.

Winter barley

Final fungicides on winter barley will be applied about now, typically around awns emergence, with chlorothalonil added if ramularia cover is required. Check latest application dates for these late fungicides as they seem to change regularly.

Winter wheat and barley should be assessed for possible late season growth regulator treatment. Spring rainfall and the extent of straw growth is the main driver and the dry spring in this area may have reduced the need for these treatments.

Nitrogen applications on wheat should be completed as soon as possible, apart from late season grain protein doses. These will be due around flag leaf emergence if soil-applied nitrogen is used, or delayed until after flowering if a foliar urea spray.

There may also be some final nitrogen doses to be applied to oat crops, as nitrogen is generally delayed on these and delaying the final dose allows a final assessment of lodging risk and hence final nitrogen total.

‘Boots splitting’

Many wheat crops may reach ‘boots splitting’ at the end of the month at which point susceptible varieties should be checked for wheat blossom midge. There are still plenty of resistant varieties which means not everyone need worry about it but there are also a fair number of susceptible crops where Hagberg is important and these should still be monitored at the critical stage.

Oilseed rape flowering was a long drawn out affair in the cool spring but it’s likely most have reached full flower and will have been treated for sclerotinia. Where flowering has been prolonged, for example in flea-beetle ravaged or otherwise backward crops, a second treatment may be necessary, though this would only be a top-up and could be a cheaper option than the first.

Oilseed rape may also need monitoring for seed weevil and pod midge. Any treatments can often be mixed with later sclerotinia fungicides but remember to avoid mixing pyrethroids with triazole fungicides. Sprays are usually dictated by weevil numbers, but if these are found check the infestation is not just on headlands, but across the field, before deciding to treat.

Winter beans are a new crop for many as the rape area in the region shrinks. Crops will soon be flowering and should receive their first fungicide, as well as being monitored for bruchid beetle, which usually moves into crops from early pod set.

Spring cereals

Spring wheat and barley crops usually receive their first fungicide this month, around GS30-31. As last season, there is a range of development stages in these crops as drilling extended from February to April. But development in later sowings should be rapid enough to catch up and reach this stage soon. Short intervals between T1 and T2 in both crops mean fungicides doses need not be high.

Spring rape and linseed may still be susceptible to flea beetle. Like a lot of spring crops in general many were sown recently, and in dry soils may be establishing slowly making them particularly susceptible to these pests.

Richard Overthrow is a regional agronomist with NIAB TAG, the UK’s largest independent agronomy organisation with several research centres in East Anglia. For more details, call 01223 342495.

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