Recently by Neil Donkin

The mild, damp weather continues, with heavy mists this week reducing the opportunities for spray applications onto anything like dry leaves. We shouldn't be lulled into a false sense of security; last year the really cold weather didn't start until the last week of November.

Oilseed rape crops continue to grow rapidly and some are now above knee high (depending on the height of your knees!). The first few phoma lesions are just starting to appear, even in resistant varieties, and it's a good time to get on with a fungicide, provided that the crop leaves are reasonably dry. The addition of a sticker/extender surfactant to the fungicide is beneficial when spraying conditions are less than ideal.

Cabbage stem flea beetle larvae can be found in some crops. A pyrethroid insecticide can be added to the fungicide if necessary.

Once again rainfall across the region has been very variable, with some areas receiving heavy showers but most still being excessively dry for the time of year. In many later-drilled wheat crops germination is patchy, with seed sitting in dry soil. On the plus side, so far there is no sign of blue mould on the seed and all we need is a few millimetres of rain to boost establishment. 

Soil conditions are challenging for pre-emergence herbicides, especially on the earlier drillings, with blackgrass reaching the three-leaf stage apparently unharmed. It means that follow-up, post-emergence treatments will be applied earlier than usual and we shall have to hope that all blackgrass has emerged by then.

If pre-emergence treatments are having little effect on the weeds, it makes it even more important to carry out the post-emergence follow-up in the autumn, rather than waiting until spring, when the blackgrass will be enormous.

Autumn fieldwork is proceeding well. Some growers have already finished drilling, some are yet to start.

There have been good conditions for false seedbeds to do their work, with occasional showers to keep the soil moist and producing a useful flush of brome and blackgrass, to be killed with glyphosate.

Oilseed rape has established well but is growing only slowly. It's difficult to see why, as the soil is warm and growth should be more rapid. Perhaps after the rain of this weekend and a warmer week to come, growth will accelerate. It's not too late to apply a small dose of nitrogen to crops if you feel it would help.

There will be a mixed response on farms to this week's rain. Those who have finished harvest will be glad of it to help with stubble cultivations, but growers with crops still to cut will not be as happy.

Oilseed rape drilling is proceeding and the rain is very welcome for germination. There are the usual concerns about drilling rape following an application of sulfonylurea or DFF herbicides in the previous crop.

The agrochemical manufacturers advise cultivations and thorough soil mixing to six inches before rape is drilled but many crops are sown without that. Usually we get away with it, but it has been an extremely dry year, residues are likely to be higher than usual. 

Although we seem to be galloping rapidly towards harvest, with two very hot weekends dramatically altering winter crops, there are still things to do and problems to be addressed.

Most wheat crops are just about past the stage when aphids can do much harm. Aphid numbers did start to build up, but there were very few crops where treatment was warranted. Late crops of winter wheat and spring cereals still need to be checked as aphid infestations can increase rapidly and the weather is certainly in their favour.

Beans and peas also need careful monitoring for aphids. In spring beans there are now green aphids as well as the usual clusters of black. The green ones are harder to see and tend to be more widespread through the crop.

Make sure any aphicides are safe to beneficial insects and preferably spray late evening when bees are less likely to be in the crop (difficult, as bees are still foraging at 9.30pm).

There has been a decent amount of rain for some areas over the weekend, but sadly, not for all.

Most winter wheat is now in flower so safe from orange wheat blossom midge, but the later crops, with ears just emerging, still need monitoring. As grain starts to fill, all crops need to be checked for aphids in the ears. Aphid populations were building in the warm weather, but the large numbers of ladybirds in crops this year seem to be limiting the infestation. Spray only if threshold numbers are found and use a product safe to beneficial insects.

T3 fungicides have been applied in the past week though the dry conditions have deterred some growers from spraying, especially where T2 was delayed until ears were emerging .

With winter crop treatments nearly finished, don't forget the spring crops. They may have been badly affected by the drought, but they are of potentially high value so need looking after.

Rain has arrived at last over most/all of the south-west with reports of 15 to 30mm this weekend. It is a huge relief and not a moment too soon.  I suspect that wheat yields, on thinner soils in particular, may already have been compromised as tiller die-back has been evident for the last couple of weeks.

Flag leaves are emerging in winter wheat and it is time for T2 fungicides. It is  earlier than usual but crops have rushed through the growth stages in response to the dry conditions. Whilst yellow rust has been the "headline" disease over the last few weeks, septoria is, as usual, a major risk to the flag leaf. Despite the dry weather there are high levels of the disease on lower leaves and with crops being much shorter than normal, rain splash from this weekend will have transmitted spores all over the plants.

Mildew is a continuing presence in many crops and in more susceptible varieties a specific mildewicide should be added to the T2 mix.

Poor uptake of magnesium, induced by the drought, can also be corrected at this time.

Ears are emerging in winter barley which should by now have had its T2 fungicide. Disease levels are fairly low at present.

Spring barley is at the stem extension stage and T1 fungicides should be applied soon. Disease levels are low but we can expect to see rhynchosporium developing now. The weekend rain will encourage active weed growth and will aid better weed control.

Both winter and spring beans are in flower and need to be monitored for diseases and pests.  Weevil are still hitting crops, in some cases following two insecticide treatments, and aphids are likely to infest crops soon. Chocolate spot has been non-existent up to now but we can expect to see it develop in more humid conditions.

Many winter rape crops have finished flowering and no more treatments are needed. In late crops it's still worth checking for seed weevil. There have been unusually high numbers in some crops this year. The threshold for spraying is only one per plant. Any spraying should be carried out in the evening when pollinating insects are less likely to be in the crop.

Rainfall over the past couple of weeks has been localised, with heavy showers for some and nothing elsewhere. The Severn Vale had just 7.5mm of rain in March and nothing so far in April. In the drier areas, particularly on thin brash soils, crop growth has slowed.

More forward crops of wheat are approaching T1 timing, the fungicide and growth regulator being applied once leaf 3 is 75 per cent emerged.  Fungicide choice should be based on varietal susceptibilities to disease.

Mildew, a problem earlier in the year, seems to have been left behind and the main worries now are septoria and rusts. So far I have found rust only in Claire, which showed strange symptoms, only the tips of the leaves being affected. It is also worth checking for eyespot as there are fairly high levels in some second wheat crops.

Following nitrogen applications, winter oilseed rape crops are starting to extend and it is time to consider whether to apply a growth regulating fungicide now or to wait until the green/yellow bud stage.

The decision will be made taking the Green Area Index into account and varying application rate according to crop growth. Strong, sustained growth is required before application.

We are approaching the time for T0 fungicides in wheat; they usually are applied around March 20th. There is mildew in most crops as well as septoria. Wheat will very often grow away from mildew so whether a specific mildewicide should be added at the T0 stage is a matter of opinion.

The decision will be made depending on varietal susceptibility and severity of the mildew. T0 is a good time also to correct trace element deficiencies, with manganese being the most obvious requirement at present. 

It's the middle of February and just when things were looking good for the start of spring drilling, 15mm of rain over the weekend has probably put a stop to field work for a few days. That's annoying, but with less than 150mm of precipitation from rain and snow (Vale of Severn figures) since the start of October, we do need the rain.

Beans and barley will be drilled at the next opportunity and both crops will need pre-emergence herbicides for grass and broad-leaved weeds. Choice of product will depend upon the weed spectrum expected. There are few options for post-emergence grass weed control in spring barley and even fewer for broad-leaved weeds in beans, once the crop has emerged.

Oilseed rape crops have, on the whole, come through the winter very well. However, there are high phoma infestation levels, particularly on varieties with low resistance. As there are also reports of light leaf spot beginning to develop, an early fungicide is advisable, applied as soon as possible. There is no need for any growth regulation at this stage so a flusilazole product would be the preferred option.