Fruit and vegetable crop protection - crop defence update

Clearer legislation and higher demand are driving a new generation of bio-pesticide products to help growers protect their crops, Claire Shaddick finds.

Powdery mildew: AQ10 targets problem specifically
Powdery mildew: AQ10 targets problem specifically

Despite establishing a special scheme for registering bio-pesticides in 2006, the Chemicals Regulation Directorate is still coming under fire for the way these materials are regulated and the cost of doing so. The directorate is currently reviewing the approach that the UK takes to bio-pesticides.

But while only two new bio-pesticide products have reached the UK grower market this year (see panel below), consultant Roma Gwynn of Rationale Biopesticide Strategists predicts more are on the way thanks to several factors. One reason is that the new EC regulation governing the placing of plant protection products on the market, 1107/2009, which came into force in the UK last year, prescribes timelines for different stages of the approvals procedure so companies making the application know how long the process should take.

A second reason is simply the increasing demand from growers. That demand is attracting the interest of global manufacturers of chemicals, such as Bayer, who are snapping up the smaller companies that have until now been largely responsible for product development.

Active ingredients

Even so, Gwynn says the number of active ingredients for bio-pesticides included or pending inclusion on Annex 1 - the European list of registered actives - has jumped from fewer than 70 two years ago to around 100. "And we are now starting to see a new generation of bio-pesticides come onto the market," she adds.

The listing also now includes 28 pheromones - compounds insects use to signal to each other. Gwynn says some pheromone-based products registered to use for crop protection should be on the market by next year. That will open up new opportunities for growers of orchard and plantation fruit crops in particular to trap and control pests rather than just use these types of natural compounds in lures to monitor pest movements.

The SCEPTRE research project is including a range of bio-pesticides in its screening programme and that will also help to speed up the arrival of new products on the market. "It's helping to give confidence to bio-pesticide manufacturers to consider the UK as a market, which they might not have otherwise done because of its relatively small size," says Gwynn.

Growers also need confidence that bio-pesticides will work for them. The four-year project, funded by Defra through the Horticulture LINK programme, with the support of the Horticultural Development Company (HDC) and a consortium of industry partners, is testing the effectiveness of a range of products, novel or already on the market, in controlled conditions. In its first year, 44 bio-pesticides, based either on micro-organisms or botanical extracts, alongside 51 conventional chemical products were offered for testing against pest, disease and weed problems identified as a high priority in various edible crops.

"In the first year we evaluated treatments on their own and then we will see how they might fit into programmes," says project leader Tim O'Neill of ADAS. "We chose products with active ingredients that were on or are being submitted to Annex 1, which cut out a number from the start. To get the best out of the bio-pesticides, we applied them preventively and more frequently than the conventional chemicals as recommended, because some induce plant resistance so the plant has to be primed, and at more closely spaced intervals - every seven days rather than 10 or 14 days."

Some of the products that gave at least a 50 per cent reduction in pest infestation or disease infection are being taken forward to the next stage. "Fewer biological treatments showed an effect overall and those that did had a smaller effect compared to chemicals," he says. But the work will also look at how the effectiveness of some bio-pesticides could be improved by different techniques. "In stored pears, for instance, we are concentrating on control of Botrytis because at present there is only one fungicide growers can use and a lot of pressure on them to use no conventional chemicals. We got some control with several biological materials and will now look at using them differently to improve efficacy - such as different rates or mixtures or by applying them as orchard treatments to get the microbial products established before fruit is harvested."

There may be other ways of making more effective use of bio-pesticides. In an HDC project, Warwick Crop Centre director Rosemary Collier is looking at whether combinations of bio-pesticides, or using them in programmes or mixtures with chemical treatments, could improve field vegetable pest control. A research review has suggested that there could also be potential in using them together with pheromones that alter insects' behaviour, causing them to come into more frequent contact with the bio-pesticide. Fargro is running trials to see whether vine weevil control could be enhanced by using the fungal-based bio-insecticide Met5 in tandem with insect-pathogenic nematodes.

Doubling up

There is also the prospect of being able to use one bio-pesticide to do two jobs. Met52 is one of three fungal bio-insecticides being tested in an HDC project to see whether they can also control plant diseases. "There is evidence that a number of bio-pesticides have a broader action than the label indicates," says Fargro technical director Paul Sopp. "This is an area that is not being widely looked at anywhere yet."

In the meantime, because bio-pesticides work mainly by contact action, Sopp says application technique is key. "There are big gains to be had from improving application, for instance by making sure equipment is properly calibrated and used," he adds. "Growers do need more management skills to get the best out of bio-pesticides."

That bio-pesticides are a more costly solution compared to conventional chemicals has been a criticism, but Sopp says the newer products are closer on price. In situations where resistance to a chemical is reducing control or where there is a risk of residues, bio-pesticides could be the only option open to growers, making them more cost-effective than the alternative.

Tomato Growers Association technical officer Phil Morley says: "Use of microbial bio-pesticides depends on a greater understanding of the biology of the micro-organism and the environment it's being used in - and its limitations." He believes the move towards a more biological approach, be it finding a place for bio-pesticides in crop protection or new thinking on soil or substrate management, heralds a major shift in crop production. "We're on the cusp of something extraordinary."

New products

Two new bio-pesticides have been introduced so far this year, AQ10 and T34 Biocontrol. Both are bio-fungicides and both are marketed by Fargro.

Based on a strain of the fungus Ampelomyces quisqualis, AQ10 is the first bio-fungicide to target powdery mildew specifically. Formulated as a water-dispersible granule containing A. quisqualis spores, sprays need to be applied preventively, when weather favours development of the disease but before mildew symptoms are obvious. It can be applied right up to harvest.

AQ10 has on-label approval for a range of protected edible crops and off-label approval for a number of other protected fruit, herb and ornamental crops. Fargro is also looking to secure approval for use on organic crops.

T34 Biocontrol has a strain of the fungus Trichoderma asperellum as its active ingredient. It has initially been approved to control root disease Fusarium oxysporum on dianthus and can be applied in a variety of ways.

However, it has activity against a range of diseases and Fargro is working on obtaining Extensions of Authorisation for edible crops. The company is also looking to launch another two new products for edible crops next year.

Bio-herbicides

There is only one bio-herbicide approved in the UK, Barrier H for amenity grassland, so a number of novel bio-herbicides are being included in the SCEPTRE project. "We are looking at as many actives as we can - four on perennial weeds and five on annuals - in container and pot trials at first," says ADAS weed research scientist Lynn Tatnell.

Bio-herbicides can be based on micro-organisms such as fungi and bacteria or on phytotoxic compounds that they produce, or on plant extracts such as citronella. "The products we are testing are all plant extracts and work by scorching the plant," says Tatnell. "They aren't translocated and there is no residual effect. Regrowth is the great problem with perennial weeds so we are monitoring the pot tests to see whether two applications are needed."

One product is looking really promising, particularly on key annual species. "One issue with bio-herbicides based on plant extracts is that applications need a very high water volume. Our tests have so far only looked at one water volume but we are talking with the manufacturer about work on volumes and application rates."

Tatnell says there is also scope to look at these products further under the Horticultural Development Company's fellowship awards scheme, where ADAS is being funded to develop the expertise of its trainee consultants by conducting applied weed-control research.


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