Green recovery to yield more from small oilseed rape

Oilseed rape crops held back by the persistent cold conditions will need all possible help now to put on rapid growth over the spring, and to maintain green leaf area for extra days later in the season to boost yields and oil content, advises Syngenta Oilseed Rape Manager, Simon Parker.

"Where growers got oilseed rape in before the September rains there are plenty of plants there, albeit relatively small compared to recent seasons. There is great potential, if the crops can be brought on through the spring," he adds. However many of the sparse crops that went in late and were slow to establish in dry late autumn conditions have also been hard hit by marauding flocks of grazing pigeons.

Growers may need to consider an early nitrogen application to give small plants a kick start for the spring. "But avoid temptation to apply too early if weather conditions are still frosty, which could damage leaves and prove counter-productive," he warns.

As well as getting small plants growing quickly as soon as spring weather conditions warm-up, Mr Parker highlights growers can compensate by extending the growing season with an Amistar application. Treatment in March and early April will retain more green leaf to enhance pod fill, raise the oil content of seed and increase yields. Independent trials have shown Amistar can retain up to 20% extra green leaf area in the all important post-flowering period, when the crop is filling the seed in pods.

He points out that Amistar is the most widely proven strobilurin approved for oilseed rape. "Growers have seen the physiological greening effect of Amistar in many crops; oilseed rape has possibly the most to gain from the increased capture of sunlight and conversion to oil." In a recent survey of growers over 60% named Amistar as the number one oilseed rape fungicide for yield.

For optimum results Mr Parker advocates a two-spray programme, with the first when the majority of the crop is at yellow bud and a second when it reaches early to mid flowering. "Since fewer crops are expected to need any growth regulatory fungicide this spring, the early Amistar will be even more important," he advises. "The first spray optimises seed numbers and can maximise yield; the second will enhance green leaf retention, help to complete pod fill and increase the oil content of seed."

Two Amistar applications also give extended disease protection throughout the flowering period, which can go on for six to eight weeks in some crops and inevitably leave some plants unprotected with a one-spray fungicide programme. "The severity of Sclerotinia attack is entirely dependent upon weather conditions during the flowering period. If there is only limited incidence, as seen last year, growers may not get their money back from a straight fungicide; with Amistar they still get the yield and oil content boost to deliver a profitable return," he adds.

Pollen Beetle timing

Mr Parker also warns growers to be extra vigilant for signs of Pollen Beetle on thin crops this season. "Treatment thresholds should be reduced on thin crops, where growers can not afford to lose any buds and potential pods to pest damage. Backward crops are especially susceptible if large numbers of Pollen Beetle migrate in from earlier flowering crops," he adds.

Hallmark Zeon remains the most cost effective option for fast knockdown of oilseed rape insect pests. Insect monitoring has identified little or no increase in pyrethroid resistance spread in recent seasons. "Growers should continue to follow IRAC advice, but outside of the far south-east and coastal regions, it should pose limited risk or restriction," he adds.