CHEMICALbriefs:

A n emergency authorisation for Certis' organic blight fungicide, Cuprokylt, has been granted – it is the only fungicide available to organic potato growers for the control of late blight.

The EAMU – driven by industry leading stakeholders, including Certis, Agrii, the AHDB, NFU and numerous organic growers associations. The use of its active ingredient, copper oxychloride, will available until September 28, 2018.

“Being able to utilise copper oxychloride will support organic growers and help them to capitalise on market demand,” said Nick Winmill, Agrii's potato development manager. “Without copper, only cultural control methods are available for the control of late blight in organic potatoes, and as a result it’s been difficult to keep varieties with preferential qualities blight free."

He added that if another EAMU isn’t secured for copper oxychloride next year, or if an alternative isn’t found, then organic potato growers face an uphill battle. “Although blight resistant varieties are available, these don’t necessarily meet consumer demand for cooking and taste qualities,” he said.

The regulatory process includes proper paperwork and adherence to strict spraying guidelines. It should be applied at a maximum individual dose of 0.85kg/ha, combined with 1100-1,300 litre of water and can be used six times per crop ,with a 10 to 14 day interval between each one.

The emergency authorisation lasts for 120 days and will expire on 28 September 2018.

New option for OSR weed control

Oilseed rape growers now have an alternative weed control strategy, with a new herbicide which can tackle broad-leaved weeds has been approved for use in the UK.

Belkar will allow growers to see crops establish before tackling key competitive weeds, without the risk associated with applying pre-emergence sprays.

John Sellars, from Corteva Agriscience, the agricultural division of DowDuPont, said Belkar was a game changer because it added a level of flexibility never seen before in oilseed rape weed control. The oilseed rape herbicide product manager, said: “For years growers have invested in pre-emergence herbicides before they see crops or weeds coming out of the ground.

“Belkar will allow them to wait and see what they have in the field before deciding on the best strategy. The extreme weather we’ve seen over the past 12 months served as a timely reminder that we never know what is around the corner, so we need solutions that can help manage the risk and volatility of growing oilseed rape.”

It contains arylex, a new active ingredient for oilseed rape, which delivers robust control of key problem weeds in variable temperatures. Its spray period is from September to December and in field trials it has controlled cranesbill, cleavers, poppy, shepherd's purse and fumitory.

Mr Sellars said a limited volume of the product would be available for this autumn, but significant volumes would be available in autumn 2019.

New multi-purpose fungicide

BASF is launching a new multi-purpose fungicide for speciality crops this autumn. Perseus contains two fungicides in its formulation – 75 g/litre of fluxapyroxad (Xemium) and 50 g/litre of difenconazole. The former is a new SDHI fungicide with broad spectrum activity and difenconazole is a well-known triazole with excellent selectivity in speciality crops.

Robert Storer, of BASF, said that Perseus was active on powdery mildew, alternaria (light and dark leaf spot), mycosphaerella (ringspot) and sclerotinia – some of the key diseases in vegetables. It has label recommendations for lettuce, potatoes, carrots, broccoli, cabbage, cauliflowers and Brussels sprouts.

Potential EAMUs could be leeks, spring onions, root and tuber vegetables, herbs, spinach and baby leaf crops.

Harvest intervals are three days for potatoes, seven days for carrots, peas and artichokes and 14 days for cabbages, spring onions and lettuce. Growers can apply three applications of it to brassicas, one to lettuce, four to potatoes and two to carrots.

With one hour’s rainfastness, it has a persistent nature and in field trials for the control of powdery mildew in carrots, the untreated area had 15% severity of attack but Perseus reduced this to 4%. For alternaria in carrots, the untreated had 24% disease severity but Perseus reduced this to 5% and in cabbages it again gave the best treatment.

In the important Scottish crop of Brussels sprouts, untreated areas had 14.7% severity of mycosphaerella but Perseus reduced this to 1.1% and in other trials sprout crops had 12.5% alternaria, reduced to 0.9%. Cabbages showed a similar response.

Re-invented chemistry

A modern version of a traditional insecticide has returned to the market to help protected ornamental growers control glasshouse and tobacco whitefly.

Applaud 25 SC (buprofezin) is a welcome addition to the armoury, said Selchuk Kurtev, Certis’ IPM manager. “The presence of a small number of whitefly can quickly reproduce to high population levels, which can cause significant problems if left uncontrolled."

It is an insect growth regulator which successfully controls whitefly in egg, nymph and pupae growth stages, before they have a chance to develop into adults and reproduce.

Whitefly is a year round pest that overwinters well in UK and become active in warmer temperatures between 10°C and 35°C. The recommendation is for Applaud 25 SC at a max of 80ml per 100 litres of water, but growers must not exceed 1200-litres of water volume per ha, with any second application after a minimum of 22 days.