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Keep those brassicas in good shape over summer

Published on 04/02/2021

Quite a lot, when it comes to forage brassicas. If your farmers are among the many who have moved towards sowing forage brassicas later in summer – or maybe even planting in autumn – it’s time now to make sure they have adjusted their crop protection input decisions accordingly.

That’s the advice from Corteva Agriscience national sales manager Richard Brenton-Rule, who says selecting the right post-emergence herbicides in particular assumes new importance in such situations. That’s because residues and plantback intervals of some products can become limiting for the next crop in the rotation.

Going by product orders, he believes the peak sowing season for spring forage brassicas has moved up to a month later over the past 10 years. At the same time there has been increase in autumn sowing of crops like forage rape and turnips for winter grazing, especially in the North Island. “Seasonal conditions have pushed some of those spring plantings later than what we would have traditionally expected,” he says. “And we’re also seeing more crops like forage rape and turnips sown in February and March for winter grazing, as farmers reach autumn after a dry summer and realise they need feed for winter. It just gives them a bit more flexibility.”

Regardless of the cause, the upshot is a narrower interval between forage brassica herbicide application, for example, and the following crop. It’s a scenario where using Korvetto for post-emergence weed control can make a valuable difference, he says .

“Korvetto’s short plantback is a standout feature, no matter when crops are sown. But in these situations, where planting dates are significantly later, it really comes into its own. It’s the most flexible post-emergence option available, with a three month plantback for clover and a six month plantback for fodder beet. Some other herbicide options have plantbacks of 9-24 months, which can be quite limiting.”

Korvetto plantback periods for maize, cereal, ryegrass and forage brassicas are nil; vegetables and legumes other than clover are six months. 

As well as controlling key forage brassica weeds like fathen,nightshades and Californian thistles, at 1 litre per ha Korvetto provides best-in-class control of shepherd’s purse and fumitory, Brenton-Rule points out.

Crop safety is excellent for leafy 
and bulb turnips, kale, forage rape and swedes. “Another important benefit is that it is registered for aerial application which means customers are not solely reliant on ground-spray. That’s good to know when conditions are such that site access is an issue.”

Sowing forage brassica crops later in spring, or in autumn, also has implications for insect pest monitoring and control, he says. “In the warmer conditions of summer, pest numbers can increase rapidly, raising the risk of the crop being severely impacted. It’s important to keep a really close eye on those crops to make sure pest populations are dealt with before they explode. 

Brenton-Rule says where required, IPM-compatible Transform and Sparta offer farmers a welcome alternative to older chemistry such as synthetic pyrethroids (SPs) and organophosphates (OPs), which are very harmful to beneficial insects. “It’s time to move on from using OP or SP chemistry for springtail, leaf miner, caterpillars and aphids in forage brassicas, and utilise the more sustainable and IPM friendly options available.”

Transform contains the novel active Isoclast (Group 4C) for excellent aphid control, with a different mode of action to other commonly used aphicides, high end user safety and low environmental risk. Isoclast belongs to a unique insecticide group known as the sulfoximines which do not have cross resistance to any other insecticide group, making Transform an ideal rotation partner for insecticides with alternate modes of action in resistance management programmes. Key points of difference include Transform’s ability to provide longer residual control than some of the alternatives, Brenton-Rule says.

Sparta (spinetoram) controls diamond back moth and white butterfly caterpillars, looper caterpillars, leaf miner and springtails in forage brassicas. Its unique chemistry provides powerful control of diamond back moth and white butterfly that out performs current market standards. It is also very effective at controlling other pests such as leafminer. Users appreciate its speed and efficacy of kill, lack of smell, low tox profile and low application rates.

In addition, Sparta’s unique mode of action means OP and SP resistant insects will be effectively controlled, plus it provides an ideal option for resistance management as a rotation partner to other IPM compatible chemistry such as the Group 28’s.

For more detail talk to your local Corteva Agriscience territory manager

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