Top disease control, high yield responses and greater flexibility in its use are just three reasons for growers to use the new SDHI fungicide, Adexar, next spring, BASF believes.

Emerging from over 1,000 candidate SDHI formulations the firm tested to find a successor to Tracker, fluxapyroxad, branded Xemium by BASF, was designed specifically to have curative activity, Ulf Groeger, BASF’s global strategic marketing manager for fungicides, said at the product’s press launch.

“We started with boscalid and systematically changed parts of its chemical structure to find a product with exceptional mobility, as well as broad spectrum activity and a good regulatory profile.”

The chemical structure explained Xemium’s excellent curative and protectant disease control (see p50), his colleague Steve Waterhouse said.

After being sprayed onto a leaf, some of the deposited Xemium was immediately available to be taken up into the leaf, which was essential for systemic movement in the leaf and curative action.

“To move systemically and the rapid uptake is unusual for a SDHI fungicide.”

Xemium started being taken up by the leaf within two hours, tests showed, and spread to cover the full leaf after one day. “It is akin to triazole fungicides in its movement up the leaf.”

But as well as a proportion of the chemical moving into the plant quickly, a large proportion was adsorbed into the waxy leaf surface, creating a depot for persistent protection, he said.

In addition, a small proportion could be transferred via leaf dew or rain to leaf axils. That allowed the chemical to be taken up by new growth, he said.

“Most other contact fungicides are either not sufficiently soluble, or not sufficiently active to give functional activity on new growth.”

That potentially allowed growers to start fungicide applications slightly earlier without much loss of efficacy, although Mr Waterhouse stressed using the optimum timing would give the best results.

The product’s excellent curative activity also allowed more yield to be retained in applications were delayed for any reason compared with other fungicides, he said.

Indeed in one trial, applying Adexar 20 days after the optimum timing for T2 still gave higher yields than a well-timed Ignite spray, he said. “It shows the power of the formulation.”

Adexar recommendations

Adexar would primarily be targeted at the flag leaf timing, Peter Hughes, BASF UK fungicide product manager, said.

“It has a fit at T2, and we have a flexible rate we will be recommending. In low disease, primarily protectant situations a half rate 1.0 litre/ha should be robust enough.

“But where disease pressure increases, and particularly if you’re moving into a more curative situation, then we would recommend a higher rate up to 1.5 litres/ha.”

In two high disease pressure trials last season, Adexar gave 1.3t/ha extra yield over Ignite + Comet at 1.25l/ha compared with a 1.0t/ha yield response from 1.25 litres/ha Aviator Xpro, and 0.5t/ha from 1.0 litre/ha of Seguris.

In two low disease trials, those responses were reduced to 0.3t/ha over Ignite + Comet, from a half rate Adexar. That was still cost effective, he said. “Adexar does have a place in low disease pressure situations.