As I write, in the middle of April, the weather forecast for the week ahead looks rather confusing. It seems to be showing very unfamiliar sunny symbols and potential temperatures in the early to mid-20s, something which hasn’t been seen for a good while now. Finally it looks like we are entering a week where sprayer wheels will be turning and spring drilling finally getting underway.
Most spring crops in my area are yet to be drilled, in some cases spring beans and spring wheat have been substituted for something with a later drilling window. Up until this week, soil temperatures have remained low and any spring crops which had been drilled have had a very slow start, some taking three to four weeks to emerge, something you would not expect nor want from your spring crop emergence. But nevertheless, a warm, dry spell should allow for the majority of spring drilling to be completed before the end of the month.
T0 plans on winter wheat were put in place back in March, but with most growers not having the chance to travel, time has pushed on and growth stages are fast approaching T1 rather than T0. Therefore, many of my T0 plans have been converted into T1s. For most, the target leaf for T1 (leaf 3), is not fully emerged but is starting to show. I would suspect that with some good weather and the amount of nitrogen underneath the crops, it will take very little time to reach this T1 timing.
With T0 plans becoming T1, this in essence has meant a pass through the crop has been missed. In most cases, disease pressure remains controllable and a good T1 will cover for the lack of T0. More worryingly, some crops have now received 75% if not 100% of their total nitrogen with no growth regulation yet to be applied. Where varieties with high lodging risk are being grown, growth regulation in with T1 plans will be bolstered accordingly.
Oilseed rape crops appear to be seven-10 days behind on flowering compared to the same time last year. Most crops are currently sitting at the green to yellow bud stage. It is this timing which poses the highest risk of pollen beetle damage, this being due to beetles boring into and killing both the green and yellow buds of the crop. Once the crop begins to flower, pollen becomes abundant and the need to bore into these green and yellow buds no longer exists. After walking oilseed rape today [April 20] first impressions would suggest that in some areas, beetle levels look high. However, it should be noted that thresholds for this pest may be higher than expected:
Therefore on many of the crops I look after, the threshold currently sits around 18 beetles per plant and many crops do not currently warrant spraying. Where plant populations are low, it may however be justified to spray. Nonetheless, a close inspection of the crop should be made prior to spraying as pollen beetles become pollinators rather than pests once the crop starts flowering. With temperatures this week set to soar, I would suspect crops will move from green bud through to flowering very fast, and the risk from pollen beetle only lasting for a very short period.