A trace of lenacil is the key to the faster speed of activity and greater weed control from Bayer CropScience‘s new sugar beet herbicide Betanal MaxxPro.

But the lenacil, a beet herbicide in its own right, is being used as an activator for the new ratio of phenmedipham + desmedipham + ethofumesate in Betanal MaxxPro.

“The micro-rate is too low to be herbicidally active,” explains Neil Thompson, sugar beet product manager for Bayer CropScience. “But it blocks stomatal control in the weed leaf.”

Stomata are the pores in the leaf surface through which carbon dioxide and oxygen enter for photosynthesis and respiration, and where water vapour escapes.

Both phenmedipham and desmedipham inhibit photosynthesis, so when the weed attempts to photosynthesise more in response to the carbon dioxide entering through the stomata, it results in damaging free radicals being produced, and faster necrosis of the weed.

“It helps nip the weed in the bud before it puts out any new leaves, which helps it to survive treatment,” Mr Thompson says.

The product also has a new oil dispersion (OD) formulation, which is designed to give quicker spreading of the spray solution over the leaf surface and increase uptake of the active ingredients. “That has allowed us to decrease the amount of phenmedipham and ethofumesate compared with Betanal Expert.”

In trials, improvements in the control of most of the weeds that Betanal Expert struggled to control alone have been seen, including knotgrass, common orache and volunteer oilseed rape.

“We expect the product to be used in the same way as Betanal Expert as the core of the programme, with there being some trigger weeds for the use of a partner product.”

Betanal MaxxPro is being launched at what would have been the 2011 Betanal Expert price – a 3% rise on 2010 in line with inflation, Mr Thompson says. “Betanal Expert will not be available in 2011.”

Bayer CropScience video showing the difference in coverage of its new sugar beet herbicide vs the standard.

Bayer CropScience video showing control of fat-hen with its new sugar beet herbicide

Bayer CropScience video showing control of cleavers with its new sugar beet herbicide

Bayer CropScience video showing control of black bindweed with its new sugar beet herbicide

Using Betanal MaxxPro allows growers to follow a flexible weed control strategy, which over seven years of trials at Broom’s Barn Research Station has increased yields by 10t/ha compared with the “basic” strategy of pre-emergence spray followed by a phenmedipham plus residual, says Mike May, the station’s weed control expert.

The extra activity in products, such as Betanal MaxxPro and Betanal Expert, allows growers to spray larger weeds, typically at first leaf rather than cotyledon, he explains.

Other advantages of employing a flexible strategy include having more flexibility in avoiding conditions that might mean the herbicide is damaging to the crop, such as hot or cold weather, and reducing the number of spray tank wash outs.

Typically, the flexible programme costs around £125/ha compared with £90/ha for a basic programme. “That £35/ha outlay requires about a 1.5t/ha yield increase to pay for it, but in trials we’ve seen a 10.8t/ha increase, which is a £200/ha return on investment at current beet prices.”

Betanal MaxxPro

Contains 60g/litre phenmedipham + 47g/litre desmedipham + 75g/litre ethofumesate + 27g/litre lenacil

Oil dispersion formulation (OD)

Same dose rates as Betanal Expert product it replaces

Offers quicker activity and better control

Low-rate lenacil activates activity