Sunday, November 19, 2017

Spray to get most from cereal crops

March 29, 2013 by  
Filed under Crops

Tweaking sprays according to crop condition will be especially important this season, writes Richard Overthrow.

Earlier sown winter wheat crops usually receive a T1 fungicide this month. Later sown crops will obviously be later developing but in these the critical target leaf 3 often emerges early so leaf emergence should still be checked carefully.

The timing of T1 sprays may not differ much between the two. Later sown wheats may still be a due a T0 but again later sowings tend to compress development so they may reach GS31/32 without needing a T0 (unless yellow rust threatens in a susceptible variety).

Nitrogen top dressing should be completed this month on winter cereals, apart from any protein doses on milling wheats. Urea applications in particular should be made fairly early in April.

Many wheat crops may appear to be at low risk of lodging but these should still receive at least a reduced dose chlormequat, as a low cost insurance measure. More forward or ‘normal’ crops usually benefit from two such sprays so the second part of the sequence, if used, will likely be needed on these soon.

Winter barley crops may now be at the stage when growth regulators and T1 fungicides need to be applied. Early chlormequat at GS30 is not a routine input for this crop, being needed only for the higher lodging risk situations such as weak strawed malting or six-row varieties. However late sowing increases straw length, and hence lodging risk in winter barley so more crops could be in this category this year.

T1 fungicides are usually applied around GS31 and represent the higher input part of the programme. At this stage it is difficult to know which diseases will be prevalent so the T1 spray should cover as many of these as possible.

Oilseed rape crops are causing many dilemmas this season. Small plants due to poor growth conditions and attention from various pests left many crops unable to compete with weeds and a considerable amount of spring herbicide was needed.

The sparse nature of these crops, making them look more like spring rape, also made them more susceptible to pollen beetle, a pest rarely needing treatment in winter rape.

Some particularly late developing crops may still be at the pre-flowering susceptible stage and should be checked regularly for this pest. Increasing resistance to pyrethroid insecticides also means alternative modes of action may be necessary to get reasonable levels of control.

Better, more-developed crops with larger plants will still be able to cope with any feeding on green buds but if these crops stay at this stage for any length of time then treatment may be needed here also. Once the crop is in flower the danger has passed and any beetles present become useful pollinators.

The better crops may also be in full flower before the end of the month and so flowering fungicide treatment will be needed. This has become a routine input for rape, mainly targeting sclerotinia and the optimum timing is usually early-mid flower.

Any nitrogen applications still to be made to rape crops should be applied as soon as possible this month, even to the backward crops.

Spring drilling can be completed with spring rape and linseed crops going in (hopefully spring cereals and spring beans have been in for some time), and any peas still to plant. As mentioned before, the spring oilseeds need to emerge rapidly and vigorously to grow away from pests and weeds, so this is usually the ideal drilling window for these.

With soil temperatures staying low well into March, spring bean crops sown early were slow to emerge and so should be continually monitored for pea and bean weevil.

Spring wheat and barley crops may be ready for their first fungicides at the end of the month (GS30-31). Neither respond to high input at this timing so don’t spend too much. Any remaining nitrogen applications on these crops should be made soon, again before a possible drought threatens to compromise uptake.

Richard Overthrow is membership services manager with NIAB TAG, the UK’s largest independent agronomy organisation with several research centres in East Anglia. For details about NIAB TAG services and advice, call 01223 342200.

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