February 2012 Archives

Warming air and soil temperatures alongside extending day length have prompted crop growth and development. Growers have responded by starting nitrogen & sulphur applications to oilseed rape, barley and "less forward" wheats.  Nitrogen applications to more forward wheats should be delayed until mid-March to help manipulate tiller numbers and reduce lodging risk. 

The first spring pesticide applications are under way. These include spring weed control in OSR for thistles, mayweed and cleavers with a clopyralid-based sprays such as Galera (clopyralid + picloram). To avoid crop injury these applications should be completed before buds are raised above the canopy. 

Spring post-emergence grass weed applications such as Atlantis (mesosulfuron+iodosulfuron) and Broadway products (pyroxsulam-based) can be applied when crops are actively growing. Overwintered grasses should be targeted while they are relatively small and soil conditions are moist.

To maximise the efficacy of spring grassweed control follow the manufactures guidelines, paying particular attention to spray quality and when control is difficult avoid tank mixing.

 The cold weather in February has certainly helped with keeping mildew under control in cereal crops and put a slight brake on the forward crops, we got as low as -8-9c. Due to the dry conditions most clients have been applying P&K for the last three weeks or so when ground was not too sticky.

Spring barley drilling has started this week on the light land and I suspect quite a bit will be done this next 10-14 days. Wild oats continue with their emergence which should allow for earlier graminicide control. Windy conditions over the last 10 days has made any spraying to be carried out somewhat problematic.

Winter barley crops now looking rather yellow which I think is partly due to a lot of lower leaf senescence due to mildew being killed off by frost and the need to start getting nitrogen on, which will start this week. Some very forward crops are approaching the end of tillering, but these are the exception rather than the norm.

Rynchosporium and net blotch levels are not significant and not looking at any major amounts of T0 fungicide applications. Manganese deficiency is starting to kick in and some crops will need manganese applications over the next 10 days.

Despite some cold nights earlier in the month the generally milder weather has allowed winter crops to grow on quietly. Winter barleys and some oilseed rape crops are starting to look as if they have used up all the currently available nitrogen.

However, with the NVZ start date passed and with the ground being on the whole fit to travel, there is an opportunity to apply the first top dressing of nitrogen plus sulphur. Sulphur is now in almost permanent deficit in this part of the country.

Winter barleys, in addition to nutritional stress, are also carrying various levels of disease dependant on variety. Mildew, net blotch and rhyncosporium have all been spotted. A T0 spray will pay dividends. This need not be too complex as long as there is a mix of actives to counteract the possibility of fungicide resistance build up.

The cold spell put paid to plenty of cereal leaf and has definitely helped reduce the disease reservoir. Even so, yellow and brown rusts are still easy to find in many of our wheat crops, septoria is not just confined to the lower leaves, and mildew continues to be obvious.

Another dry spring may relieve some yellow rust and septoria pressure, but it's unlikely to do much to keep brown rust in check. Whatever the weather, the last thing we'll be doing this season is skimping on our T0s. Especially not with such a large proportion of our national wheat acreage down to varieties with less than ideal rust resistance.

Robust rates of rust-active triazoles, with a mildewicide where necessary, will be the order of the day for most of our wheats. We won't be tempted to go in too early, though. T1 timing here is invariably around 25 April  and we know a gap of more than four weeks from T0 leaves crops wide open to rust development.

Another season begins, and already there is talk of drought and water shortages.  It went until April last year before we talked of such things!

The unusually dry winter, following on from a dry year last year, is going to pose many headaches as far as decision making is concerned. The first of these will be fertiliser timing. Soil reserves, with no excess winter rainfall, are bound to be higher than normal. Crops are also much more forward and thick than this time last year so care will be needed as far as timing is concerned.

Winter barley, we know, cannot compensate for a shortage of tillers in the way that wheat can and as a second cereal will not have access to large reserves of soil nitrogen. It therefore needs fertilising as per a normal year, with the first dose going on end Feb/early March. I will apply about a third of the total dose then. Second and longer runs of wheat will also have limited reserves, so will get the same treatment regime of about a third of the total dose end Feb/early March.

The early warnings of hosepipe bans will be like music to my Scottish colleagues, as one thing last year gave them was plenty of water! A much overlooked benefit of dry weather, from the agronomist's point of view, is how much easier it is to scout the land. Unfortunately, this usually means finding lots of horror stories.

Blackgrass looks remarkably healthy despite having had the Greek national debt spent on it. No doubt much discussion will be had on resistance, product performance and dry weather.

On the positive side crops look really well and thoughts are turning to the first application of fertiliser. Sulphur needs to be applied early to get the benefit in this growing year. Assess each crop on its merit and don't be fooled by the dry spring weather over the last three years. Large, early applications of Nitrogen will increase lodging risk and produce ideal disease conditions.

Standard deep nitrogen coring, to measure soil mineral nitrogen (SMN), is producing some highly variable results. This is not surprising if you consider the factors that influence SMN levels in January/February. This year the most variable factor is the performance of the previous crop and its utilisation of nitrogen applied in spring 2011.

In many cases in East Anglia, SMN levels are lower than we would expect in a low rainfall winter. In some cases this can partly be explained by the fact that large crop canopies have trapped considerable amounts of nitrogen. Nevertheless, the indications are that total Soil Nitrogen Supply (SNS) figures are atypically low. Second wheats seem to buck this trend with higher SNS levels, which may reflect the often poorer performance of first wheats in 2011.

If soils dry over the next couple of weeks, top dressing nitrogen fertiliser will be the priority. With the threat of another dry spring even the forward crops, especially if they are sitting on low SMN levels, will receive a dose of N. Careful PGR management of large cereal crop canopies will be needed, with robust split applications at T0 and T1 in the highest risk situations.

Crops are all over the place in terms of growth stage and canopy size this year. The early drilled crops are carrying very large canopies and a lot of foliar disease, whilst some of the later drilled crops are short on biomass and will require nitrogen early to bring them on.

In the wheat crops, septoria has replaced the autumn mildew as the primary cause of concern. In mid-Devon, between 1st Dec and 7th January, we had over 10 inches of rain and very mild weather. This has brought on the septoria with a vengeance. The mildew will still be bubbling in the background and the mild winter, with very little frost, means that brown rust will be of major concern on susceptible varieties.

The forward crops will need careful nitrogen and PGR management if we are not to face a severe lodging year. My main concern is that many growers are keen to get on with quite significant nitrogen applications early, due to the problems last year of poor uptake due to the dry weather. I would urge caution, as 2012 is shaping up to be a very different year to 2011 at the moment.

Before Christmas I said that if we didn't have a prolonged cold spell soon, with diseases creeping in to all cereal crops, we would be in for a very challenging spring. Well we've had our cold snap, and crops have certainly been held in check, but whether it has been prolonged enough to reduce disease pressure significantly we'll have to wait and see.
 
Many cereal crops still look quite lush, especially on the coastal plain and there will be no need to rush in with early nitrogen this year. The weather has not yet warmed up enough to think about follow-up grass weed treatments yet so it's still a waiting game.

Crops treated with Atlantis in the autumn have now had long enough to see how well it has worked. Any survivors need to be scrutinised to ascertain whether it is down to poor efficacy conditions, or maybe tested later for resistance. If it is the latter it signals even greater need for comprehensive strategies to deal with the problem.

The recent cold snap has thankfully put the brakes on crop growth after a long spell of mild weather.  All crops generally look very well so now it is a case of maintaining this promising yield potential.

Yellow rust was very evident in susceptible wheat varieties prior to the snowfall, particularly in more coastal areas.  The blanket effect from the snow may have limited the amount of yellow rust control despite some very cold temperatures. 

Nature has performed better at reducing brown rust and mildew levels.  However, it looks like many crops could be under a lot of disease pressure early on this spring, and that is without even mentioning Septoria tritici!

Winter arrived last week, with temperatures as low as -12C near Market Rasen (a colleague at Holbeach recorded -16C). Unlike last year, there was very little snow cover to protect the crops. 

The task of identifying light leaf spot in oilseed rape (OSR) crops will be challenging, as at first glance frost damage can appear similar.  OSR leaf samples will be heading to my airing cupboard for incubation.  This is unfortunate, as I have only just emptied the fridge of soil samples to be tested for soil mineral nitrogen. Who would marry an agronomist? 

HGCA topic sheet 75, 2003 states if 25% of plants are infected with light leaf spot an appropriate fungicide should be applied at the earliest opportunity.  With the current high value of OSR, and if the variety is susceptible to light leaf spot combined with the current cooler weather, I think we will be well rewarded for treating where infections are above 15%.

The first frost-free morning for three weeks may signal the start of spring and the time to assess crops coming out of winter.

The lush growth of some crops prior to Christmas has been knocked back, but in general cereal crops still look good and well-developed.

Winter barley that had very dense growth in autumn was, in some cases, badly infested with mildew and probably should have had a fungicide treatment. The frost that would usually suppress the disease took a long time to arrive. These crops may need a T0 treatment in March to stop the disease from developing.

There are many thick oilseed rape crops in the region on which the frost appears to have had little affect and pigeon damage has so far been minimal. Their Green Area Index is already high and will need careful assessment later to make decisions on nitrogen rates and growth regulation.

February again and is spring just around the corner? It certainly seemed like it 10 days ago with fields looking as green and advanced as a normal March. The cold snap has steadied things up and at least the Charlock looks a bit sicker now. Once again frost had the greatest effect where SOLA bifenox was applied previously.

A striking effect of the mild winter was seen last week in South Wales in a BYDV trial. Untreated plots and the guard area around the trial were heavily infected; plants in these areas had roughly half the biomass of those in the treated areas.

Most cereals have high shoot numbers and will require careful nitrogen and PGR management. Even with high levels of mildew winter barley still carries lots of tillers. Wheat is very similar with early drilled Grafton carrying 10 or more tillers. Don't forget that HGCA lodging rating is not an absolute figure and can vary by several points depending on sowing date and shoot number. Root lodging is likely to be most severe in early sown, over thick crops so take every step to keep these crops in check.

At last, a nice bit of winter though there's no promise of it lasting, but let's hope. Up until last week, we'd only had seven frosts with only one before Christmas - on 7th November.  Therefore, we have to expect significant aphid numbers and a serious threat of BYDV - unless this bit of winter lasts and particularly if we get serious cold without snow cover. It's not been cold enough yet and snow is coming.

Oilseed Rape crops have thick, strong deep roots and a nice rosette from which to develop new growth.  Thankfully, all our efforts to control Cabbage Root Fly appear to have worked as all crops inspected since New Year are free from this damaging pest.  However, I am still expecting to see crops which were not treated in autumn taken out in spring - as happened last year.  Phoma & light leaf spot levels are very low so, despite all the commercial hype, they don't require any treatment.

The cold weather has finally brought the GAI of oilseed rape crops back to somewhere close to where we would expect them to be at this time of year. Over the last month they have lost 0.75-1.0 GAI, which means that the forward crops are now allowing carbetamide applications to hit the ground where it's needed.

Two nights dropping to -10C have helped Fox (bifenox) to work on charlock. I was worried about how some crops going to look where there was more charlock than rape.

With the cold weather the pigeons are just starting to arrive but numbers are still far lower than we would normally expect. While the cold weather lasts I'm expecting numbers to increase. As long as they are not eating the crown of the plant they won't be doing any major damage, however be ready to control numbers before they do damage.

As this is being written, three inches of snow cover the ground and there have been at least three decent frosts. All this, is to my mind, is a very good thing. Many crops are just too lush and forward especially since the Christmas period, with them greening up and appearing to be taking up mineralising nitrogen. It's just not right for this time of year.

Disease levels in wheat which had calmed down during late November were being reported as increasing again, particularly yellow rust with some brown rust as well. Many people had resisted the urge to apply fungicide up to this point on the advice of most experts, but if the mild weather had continued, rethinks were on the cards.

However, this spell will certainly put a brake on things and may bring things back to where they should be disease wise anyway, time will tell.