Financial warning on failure to protect struggling rape crops

Apr 15 2008 by Sam Wood, The Journal

FAILURE to properly protect poorly emerged or late growing rapes will slash margin potentials in what is a high value crop, according to agronomy business experts.

With many crops exhibiting a range of plants with different growth stages, any pest and disease control will need to take into account a longer flowering period.

According to Cotswolds-based Lawrence Hicks, of agronomy business UAP, while some fields have good, strong, plant stands, others – particularly those that were slow to emerge and which have been pigeon ravaged – are two weeks behind. He said: “Experience suggests that in these struggling crops, we would expect at least a two-week protracted flowering period, and this is creating headaches for those who now have to manage a crop with many varied growth stages.”

As far as fungicides are concerned, Mr Hicks said that with a relatively poor yield potential growers won’t want to spend the earth. However, with rape priced at £350/t, a 0.5t/ha response this year will provide you with extra income akin to 1t/ha at last year’s prices, so it does pay to ensure you get the basics right.

Perhaps the most critical choice of input this year will be choice of insecticide. With increased pollen beetle resistance concerns and a prolonged flowering period, Mr Hicks advised growers to maintain rates and consider sequential applications.

If crops are still at green bud, and pollen beetle reaches threshold levels, then provided you don’t have a resistant population, then alphacypermethrin is an option. However, as soon as we hit early flowering, then the bee-safe tau-fluvalinate, Mavrik, should be employed. He said: “This, or the neonicotinoid Biscaya, are your only real options to guarantee good control and safety to pollinating insects.”

Mr Hicks said that Mavrik is also a good option during later flowering, when the target becomes seed weevils and pod midge. Here growers may find that in prolonged flowering crops that two full rate sprays of the insecticide will be prudent.

“In addition, because Mavrik is widely compatible with a range of fungicides including triazoles, it can be applied at the same time as targeting disease. Sclerotinia will need taking care of during flowering and here, a 0.25kg/ha rate of Filan plus Agate – mixed with Mavrik – will maintain good control, prolong green growth. Keeping the crop growing – particularly where later N has been used – gives you every chance of piling on some extra yield,” he said.

Makhteshim Agan technical manager, Stuart Hill, agrees that it has been another protracted green bud period, due to the cooler conditions. He said: “With crops at various stages within fields a sudden increase in temperature could cause a resurgence in pest numbers, particularly pollen beetle, so growers need to be ready.”