Keeping abreast of arrivals and departures in crop protection products for field vegetables and potatoes has been somewhat challenging for growers of late.

The moves in Europe to change the way pesticides are approved in future may have grabbed recent headlines, but the EU review that has been going on for the past decade has already driven a raft of products out of growers' chemical stores for a number of reasons.

Some active ingredients weren't supported through the review by the manufacturers or failed to make the EU-approved Annex 1 list - the fate of herbicides trifluralin and propachlor, for instance.

Then there have been new restrictions on dose rates imposed during re-registration of some products that did achieve Annex 1 listing, while the new way the EU sets maximum residue levels has led to the revocation of approvals for some substances on certain crops - which for some crop and product combinations were later reinstated, albeit with new restrictions, thanks to efforts by the Horticultural Development Company (HDC).

And there are other forces at work, too, such as issues surrounding the fate of pesticides that accumulate in watercourses. Arable farmers have already lost one major herbicide this way and now manufacturers of the slug control metaldehyde are recommending growers limit application rates voluntarily in order to protect its future.

As it is, horticulture is the Cinderella of mainstream farming when it comes to product introductions, says Interfarm UK technical manager David Stormonth. "It's a numbers game - the size of the potential market versus the development and regulatory cost of new products," he says.

Reduced range

The new EU approvals rules, agreed by the European Parliament in January, could see a much-reduced range of products for growers to call on in future. The Chemicals Regulation Directorate's assessment of products most likely in the firing line could see the end, for instance, of the fungicides mancozeb - which is key to blight management in potatoes - iprodione and tebuconazole, along with the herbicides pendimethalin, ioxynil, and linuron.

"On paper, the herbicide losses could cause a lot of problems in vegetable crops," says BASF field vegetable product manager Robert Storer.

Pendimethalin is approved for at least 30 field vegetable crops and many more edible herbs. "Nothing would do what pendimethalin does," says crop consultant Cathy Knott. "Nearly all of the newer herbicides don't control knotgrass and Polygonum and many don't control groundsel. It would become very difficult to control weeds in carrots, lettuce and onions."

The potential loss of pendimethalin as a pre-emergence herbicide will also be the main problem for pea and bean crops, says Processors & Growers Research Organisation technical director Anthony Biddle. Losing linuron too would leave green beans without effective pre-emergence controls. "Weed control will still be possible but we may have to accept poorer control levels," he says.

Aside from the gaps left by any future withdrawals, the risk of pests and pathogens developing resistance to remaining products would be heightened.

Iprodione, the active ingredient of BASF's fungicide Rovral WG, is the only substance from the dicarboximide group to have gained Annex 1 listing. "We would lose a product that helps in terms of minimising disease resistance by product rotation," says Storer.

Despite the uncertainty about what will stay or go, the chemical companies working on new introductions remain upbeat. "The pace of change may increase over the coming years but with more exciting new products on the horizon the old guard was changing anyway," says Syngenta speciality crops manager Bruce McKenzie. "It will be increasingly costly and difficult to register new products - but it is certainly not impossible."

New products

One of the next new products from Syngenta will be a seed treatment for potato growers based on fludioxonil, which is active against Rhizoctonia black scurf, silver scurf and black dot, and can help to reduce common scab. New advances with its potato aphicide Actara could lead to pre-formulated combinations with other insecticides.

Since Cambridge-based agrochemicals supplier Interfarm UK was acquired by Sumitomo in 2007, UK growers can look forward to easier access to new chemistry the Japanese chemical company is developing, says Stormonth. "We are working hard to bring these products into the UK," he says.

"For example, we have an insecticide which could be of interest to the vegetable sector and a useful fungicide for Botrytis control."

The company is also looking at its herbicide portfolio to see if any could have an application in UK horticulture.

Broad-spectrum control

Bayer launched the systemic fungicide Rudis earlier this year. A fungicide based on prothioconazole from the DMI cross-resistance group, it was introduced with on-label approval for leeks (controlling leek rust purple blotch) and cabbage (controlling dark leaf spot, light leaf spot, ringspot, powdery mildew and phoma leaf spot). "It offers continuity of broad-spectrum disease control with physiological benefits to plant health and quality, like the strobilurins, making it the ideal non-Qol partner in programmes," says Bayer product manager Nathan Whitehouse.

The company is working to extend the label to cauliflower, calabrese/broccoli and Brussels sprouts, anticipated in 2010, and to carrots the year after.

Bayer is also developing a co-formulation of prothioconazole and fluoxastrobin for downy mildew control in onions, which currently relies on fungicides containing mancozeb. Approval is anticipated next year.

On-label approval

Bayer's neonicotinoid aphicide Biscaya (thiacloprid) recently gained on-label approval for cauliflower, calabrese/broccoli and cabbage, and approval on carrots is being planned. Also on the way, hopefully for launching this year, is a systemic insecticide for control of sucking pests in brassicas and lettuce. Whitehouse says it will be unique in that it is translocated in the plant's phloem, so can travel up and down the plant. Systemic products normally move upwards, in the xylem. In lettuce, for instance, it will be able to reach root aphid as well as Nasonovia in the lettuce heart, while in brassicas it will take out cabbage aphid which can be challenging to control by contact sprays because of its waxy covering.

In the new landscape created by the hazard-based EU approvals scheme, some experts speculate that it will be harder for manufacturers to bring new active ingredients to market while having to spend more resources on maintaining what they are left with. The HDC has already had to postpone this year's screening of herbicides for safety and effectiveness on field vegetables through lack of new products to trial.

But as Knott highlights, any further loss of active ingredients is speculative and some chemical companies may decide to generate more data to defend their products. BASF, for example, has made it clear that it will support pendimethalin, on which several of its herbicides are based. "Until we've got some clear detail, we don't know what impact the new approvals rules will have," says Bayer's Whitehouse. "We're being proactive where we can to support our products."

And, as managing director Paul Sopp of distributor Fargro points out: "The loss of some actives as the result of the European regulatory changes will leave some gaps and although new products will fill these in time, we need to ensure that existing products remain for as long as they are needed."

But Sopp also believes that biological products, whether microbial or plant extracts, will become increasingly important in plant protection in future alongside conventional chemistry. Fargro has just launched Serenade ASO, the first foliar biofungicide to be approved in the UK. Based on a naturally occurring strain of a bacterium, its wide range of off-label approvals for Botrytis control include bulb, fruiting, leafy and stem vegetables, root crops and vegetable brassicas.

Biological products

Serenade ASO was developed by American company Agraquest, which is planning to bring to Europe another bio-fungicide that prevents powdery and downy mildew, rust and Sclerotinia, and a bioinsecticide based on plant extracts and active against sucking pests. Both are approved in the US on fruit and vegetable crops.

Sopp says: "Biological products will become more mainstream and the biocontrol champion approach by the Chemicals Regulation Directorate will result in several new products being registered in the next year or two.

"Inevitably, consumer and environmental pressure will encourage the use of biological products, but product efficacy needs to be comparable to conventional products if they are to be accepted.

"With the pressure on fewer active ingredients in the future, resistance management will become even more important and here biological products have an important role to play as they have completely different modes of action to conventional chemistry."

He adds: "They also have an important role in residue management and will replace some conventional chemistry, especially where short harvest intervals are needed."

Wider use

Biological products of long standing could be more widely used in the vegetable sector too, says Stormonth. The bioinsecticide Dipel DF, developed by Valent Biosciences of the US, also now part of Sumitomo, is based on the bacterium Bacillus thuringiensis, which targets caterpillar pests.

It is hardly new, but Interfarm UK is keen to encourage its wider use through better understanding. It has both on- and off-label approval on many edible crops. "It's a clean, green insecticide understood by those who have experience of using it," Stormonth says.

"But there are many who don't appreciate how easy it is to use and to get good results. It has no maximum number of applications and no harvest interval - there are not many insecticides with that on the label."