The cooler, wetter weather appears to have put the brakes on the pace of crop ripening this season. Many growers are now expecting the cereal harvest to begin by mid-July.

So too has the pace of maturation eased somewhat for the country’s 8,650ha of winter oilseed rape, meaning crop desiccation may be later than anticipated.

Some early sown crops, however, could be at the point of spraying off while this could be two or more weeks away in others.

If a hot and dry settled spell returns and your crop is weed-free, then natural maturation may be an option. However, with this broken weather pattern in charge for the short term at least, chemical desiccation will be required this season.

Remember, for anyone who used diquat (Reglone) as a desiccant, this is no longer permitted and your records must reflect this. This leaves glyphosate as the only other real option for growers.

When do I desiccate?

Spraying too early will result in poor desiccation so correct timing is important. Glyphosate should only be applied when the pods have less than 30% green seeds. This can be determined using the following visual test:

Step one

Select an area of the crop that is representative of the field as a whole.

Then choose an area of canopy that is typical of the maturity of most of the crop.

Depending on the canopy, this may be the pods in the middle of the main raceme or on the side branches. At random, pick 20 pods from several plants.

Step two

Open each pod and observe how many seeds have changed from green to brown or black.

If this change is observed in at least two-thirds of the seeds per pod in at least 15 of the pods picked, then the earliest correct stage for spraying has been reached. Repeat across the field.

Typically, the crop should be sprayed within four days. If the weather is very cool, however, this can be extended to seven days.

Some early sown crops could be at the point of spraying off

If approximately half of the seeds are turning brown, then the earliest correct stage for spraying is likely to be in three days, but it is important that the procedure is repeated to check that the correct stage has been reached.

Spraying

Roundup Powermax is consistent on rape. Use plenty of water (200l/ha or more) with up to 2.0kg/ha of the product or 3–4 l/ha of other glyphosate formulations.

Up to 21 days of a harvest interval may be required to allow for kill depending on the weather and crop condition.

Considerations

  • Needless to say, do not use glyphosate in crops grown for seed production.
  • Do not use glyphosate-treated straw as a horticultural growth medium or mulch.
  • Poor results can be expected from treatment of heavily lodged crops with major secondary growth or significant areas of uneven ripening (eg caused by pigeon damage or poor drainage).
  • Poor results can also be expected from lodged or brackeled crops where stems have been broken.