Archive Article: 1997/12/13

13 December 1997

A NEW herbicide molecule completely stole the show at Brighton this year. It was given the thumbs up from the major agrochemical distributors.

Why were they excited? Because this chemistry promises to be a one-hit solution to blackgrass – even resistant strains. It will also control major broad-leaved weeds including cleavers.

Discovered by Monsanto scientists, the product (known only under its code name, JV 485) is a pre-emergence residual herbicide, applied as a liquid. Control of blackgrass is ahead of nearly all other current commercial alternatives including sequences with pre- and post-emergence products, according to company results.

Thanks to its novel mode of action, JV 485 knocks out all known resistant blackgrass types, including target-site resistance (fop and dim) and enhanced metabolism resistance (IPU), said Dr Steve Moss of IACR- Rothamsted.

"We havent found any sign of blackgrass resistance to this new chemistry in the UK." But Dr Moss advised caution; resistance could evolve over time, because JV 485 appears to rely on a single mode of action. A mix of strategies would help limit the risk.

One big advantage over current blackgrass products seems to be JV 485s consistency in difficult seasons. It works in wet or dry soil conditions, and in rough seedbeds. There are no restrictions on following crops. It is not for use in barley.

Cleaver control is a significant benefit, particularly at the higher dose rate. "A spring spray against cleavers would rarely be necessary following JV 485," suggested Ben Bolton of Bayer. Monsanto and Bayer are co-operating on the marketing of JV 485.

Growers could also expect good kill of volunteer rape, speedwell, pansy, shepherds purse, fools parsley, charlock, red deadnettle, forget-me-not, mayweed, poppy and geranium. Its an impressive list; the few species which might escape full control include volunteer beans and ivy-leaved speedwell.

With remaining grass weeds, JV 485 also has some activity against sterile brome and wild oats, but these may need a follow-up spray with another product to clear up serious problems; spring germinating wild oats tend to escape. Annual meadow grass and Italian ryegrass are controlled well.

One possible drawback to this new chemistry is that it would have to be used before any weed problems became apparent; some might argue that this prophylactic approach doesnt fit comfortably with integrated crop management and the theory of appropriate dose.

JV 485 is formulated as a 500g ai/litre suspension concentrate. Application rates are low – between 125g and 175g ai/ha.

Expected commercial launch is within two years, but this is dependent on the approval process. On price, the manufacturers are keeping mum – but it is unlikely to be a cheap product.

Monsanto and Bayer have created a new joint company – Twinagro. It is to be responsible for co-ordinating the manufacture, registration and marketing of JV 485.

Other new arrivals at Brighton include mixtures containing carfentrazone-ethyl, which is the broad-leaved herbicide partner, from FMC, within the new herbicide combination Lexus Class.

This highly active molecule gives low dose, fast kill solutions (20g ai/ha) to cleavers and weeds such as ivy-leaved speedwell as either autumn or spring treatments. Not available as a straight in the UK, growers should expect to see a wider range of carfentrazone-ethyl mixtures shortly, including an IPU combination (Affinity) and with a mix with mecoprop-p (Platform S).

BETWEEN 95% to100% control of blackgrass, rye grass, wild oats and annual meadowgrass is claimed for a new AgrEvo graminicide which the company hopes to launch in three to five years.

Field trials with the new product, for which no chemical details are being released yet, show it controls resistant blackgrass, and lab trials show it overcomes herbicide resistance in wild oats and rye grass. A post-emergence material, it will be useable in both autumn and spring. It also has some effect on bromes, rough meadowgrass, canary grass, loose silky bent, couch and onion couch.

Agrevo is also planning an enhanced version of its new cereals fungicide Vista (fluquinconazole) even before its original formulation is marketed next spring.

The fungicide is said to outlast even the strobilurins with its persistence in controlling septoria and the rusts. A new formulation should be ready for 1999 and the company plans further products based on the same molecule.

New formulations of Cheetah, Puma X and Tigress are also on the way from AgrEvo, as is a new sulfonylurea herbicide combined with a safener to allow its use on wheat principally against cleavers, mayweed, chickweed but with some control of pansy and speedwell. Of the revised formulations, only Tigress will have new dose rate recommendations of a maximum 1.5 litres/ha in autumn and 2 litres/ha in spring.

WEEDS tucked up under plastic with early potatoes, carrots or maize can be controlled with herbicide printed on to the protective plastic cover for slow dispersal.

The technique has been seen to work in trials at the Arthur Rickwood Research Centre by Sally Runham of ADAS. While the crop continues to thrive in the microclimate under the film, weeds are checked by herbicide in the plastic, costing between £500 and £1,200/ha (£200-£486/acre) according to herbicide.

In early carrots, nearly 3t/ha of extra yield was obtained under the film. Weed suppression was more prolonged when linuron was applied on the film rather than sprayed at commercial rates.

Early potato yields were similar for weed control by impregnated or sprayed linuron but metribuzin did not work so well on film. The technique did not work well with low rates but it could be possible to print herbicide only on part of the plastic film, said Ms Runham.

Results from trials with maize showed similar yields from plastic or atrazine sprays.

PESTICIDE taxes and blanket limits on national agrochemical usage are now being considered in Europe as ways of reducing agrochemical usage throughout the Community – once again.

But this time around it looks as though the Commission is deadly serious about the prospect. A policy document is to be put together by 1999.

"It is highly likely that new legislation, whatever form it might take, will be introduced for plant protection products in Europe," predicted Brian Sheridan, a legal consultant working for the Commission, based in Brussels. "We should expect it within three years."

The pesticide manufacturers are worried. They are fighting hard for an alternative to heavy-handed legislation: they would prefer voluntary strategies agreed between growers, consumers and suppliers.

The industrys argument is that new laws to restrict use, or to impose taxes on pesticides would distort trade, stifle innovation, be expensive to operate and would prevent growers from being competitive on world markets, according to Dr Pierre Urech of the industrys trade body, the European Crop Protection Association.

"We recognise our social and environmental responsibilities as an industry, and that these are essential to our survival. We support integrated crop management wholeheartedly," insisted Dr Urech. "

"However, we already operate under one of the most sophisticated regulatory systems in the world. Todays crop protection products are thoroughly researched and have an excellent safety record – the environment will be much better off in a properly regulated but free enterprise culture."

Some member states, for example Denmark, already operate national schemes to limit pesticide use. These are criticised for being clumsy strategies which put growers at a disadvantage, whilst not achieving significant environmental benefits.

Dr Utrech suggested that a better approach to pesticide reduction might be through a link with voluntary farm assurance schemes. The ECPA will soon be presenting its own alternative proposals to the Commission.

For its part, the UK government has already taken the initiative on national pesticide reduction, but it is using consensus and voluntary cooperation rather than new legislation. MAFF has created a new body – the Pesticides Forum – with a brief to encourage reduction in national pesticide use, and minimise any environmental impact.

All sectors of the industry are represented, from growers, distributors and sprayer manufacturers to consumers and public servants. The committee is focusing on voluntary strategies to achieve its aim, under the guidance of Ministry scientist Dr David Shannon.

Its first action plan was produced in August. A key part of the plan is to develop a means of measuring possible environmental risk from agrochemicals.

WHY use a herbicide – if you can persuade a plant to exude its own weed control through the roots instead? It sounds far fetched, but this is just what Philippine scientists are attempting to do with rice breeding.

Strains have been identified that have natural defence mechanisms, stimulated by the presence of certain weeds. These rice plants are able to suppress competing weeds by giving out chemicals through the roots. The hunt is now on to understand this process – called allelopathy – and discover whether this natural weed control could be bred into other cereal species; rice today, wheat tomorrow?

USING low rates of hormone-type herbicide may not kill weeds outright – but such applications could be just enough to knock weeds back, and reduce seed production, germination and weed viability into the next generation, said Gillian Champion of Reading University.

These side effects are not often taken into account when considering the effectiveness of herbicide treatment. But Ms Champions research shows how common speedwell can be affected by just one-quarter dose of fluroxypyr (Starane), reducing weed seed number, weight and size. "Weed seed quality measurements should be taken into account when considering herbicide effectiveness," suggested Ms Champion.

THE race is on to discover a rapid, farmer-friendly test for blackgrass resistance. But might the French beat us to it? Scientists at the Institut National de la Recherche Agronomique (INRA), near Dijon, are looking at three options.

One method could give results in just 48 hours, and could be carried out in the field by growers at the end of winter, said Dr Jacques Gasquez of INRA.

This system uses tillers and does not require special techniques or equipment. The disadvantage is that it only checks against target-site resistance.

Two other tests, using pollen and seedlings, would be more applicable to laboratories, said Dr Gasquez. Checking pollen allows the identification of resistance to several herbicides, and seedling studies can distinguish different levels of resistance.

As yet, no quick tests for blackgrass resistance are available in the UK. Growers face a six week wait for results. However, a fast test is currently being developed by scientists at IACR-Rothamsted.

YIELD is not the only casualty of downy mildew and light leaf spot infections in oilseed rape. It now appears that these diseases can hit oil content – and so cut profits.

A preliminary survey by Dr Ken Davies of the Scottish Agricultural College has identified several such links between weeds, pests and disease and crop quality aspects. It puts an extra dimension on the dangers posed by certain crop problems.

For example, if your crop is left weedy until spring, then downy mildew and botrytis risk increases, said Dr Davies. "This effect has not been quantified before." But both diseases seems to reduce glucosinolate levels, which may be an advantage for anyone wanting to home-save seed.

Leaf miner damage in the autumn can raise glucosinolate levels, and these pests are encouraged by volunteer potatoes. Growers should therefore put a higher priority on eliminating these weeds, suggested Dr Davies.

This work is being done as the COIRE (Crop Optimisation by Integrated Risk Evaluation). "We are now evaluating which links are real, and which are spurious. We shall then be looking at environmental factors as well," he said. "Many interesting points are emerging – for example, the more annual meadow grass there is in a crop, the fewer slugs. We are trying to work out why – but it could be an advantage to keep annual meadow grass in a rape crop."

COMPENSATION should be made available to growers in return for limiting pesticide use in buffer zones, suggested Mr Terry Tooby, of the Pesticides Safety Directorate in York.

Otherwise growers will amalgamate fields – to reduce the buffer zone area – and also put pipework in to field ditches so that water is carried underground. "This is already happening," he said. "The commercial implications are serious for farmers with many small fields, and they are even now removing hedgerows and other wildlife corridors to lessen the impact. So a regulatory solution to protect one sector of the environment could backfire."

Currently 406 plant protection products require a 6m buffer-zone to be maintained from field water catchment areas. Although other EU member states use buffer zones, they are limited only to main river systems, and do not include small ditches. The government is currently considering proposals for regional risk assessment on buffer zones.

NINE cereal diseases can be detected with one multiscreen test from the Scottish-based Adgen Diagnostic Systems. At £69 for a single sample, the new laboratory test can unravel and identify the DNA from six fusarium species associated with foot rot or ear blight, from sharp eyespot, and both the W and R types of eyespot before any visible symptoms.

Adgen, from Auchencruive near Ayr, also has new potato virus diagnostic tests, including rapid on-site tests for potato viruses X and Y and for leaf roll virus. Cost of the 10-15 minute tests is £3.50 to £4.50 each with the kits which are sold in batches.

CHOICE of variety may have unwittingly been contributing to the volunteer oilseed rape load.

Rape seeds can persist in the soil for at least five years, and very likely for 10, said Carola Pekrun. That causes problems enough today for weed control in other broad-leaved crops.

But volunteers will take on greater significance in terms of contamination when the new types of rape with specific oil qualities – and there are between 10 and 20 in the pipeline – hit the market.

So work at IACR-Rothamsted is establishing the potential of existing spring and winter UK varieties, including those currently with high erucic acid, to develop secondary dormancy.

What it found was a big range between varieties, from 0.7% dormant seeds to almost 80%.

And the worst variety? Only the most popular variety for the past four years. Yes, Apex. While Dr Pekrun admitted that some variation between experiments casts some doubt on the reliability of her test procedure, theres no doubting Apexs prominence in each. "We can say it would be prone to build up quite a high seed bank," she said.

By repeating the experiments, its hoped an average response for all varieties can be given with more confidence.

This knowledge probably wouldnt affect growers variety choice at the moment, Dr Pekrun thought, but it may do in the future. She suggested that assessing dormancy might be beneficial for breeders screening new varieties.

CLASSIFYING spray quality into coarse, medium and fine, after 12 years, is set for an update. A second set of categories is being introduced by the BCPC to define the potential of a nozzle to produce driftable droplets.

This is important for growers following specific field margin management strategies. Driftability will be assessed in wind tunnels or other controlled situations, related to reference nozzles, then categorised using mathematical models in an international scheme developed by the Rotterdam Group – an informal group including specialists from R&D organisations and nozzle and sprayer manufacturers.

The proposed system needs about six months more work. One of the most pressing issues to be resolved is how to set spray quality categories for twin fluid and air inclusion nozzles, such as the Lechler air injector, Lurmarks Turbodrop or Billericay Farm Services Bubblejet.

While these have a dramatic effect on the performance of spray, their density and transport characteristics are quite different from conventional nozzles, so defining spray quality is proving quite difficult, explained Ted Southcombe, chairman of the BCPC Applications Committee.

ITS official – herbicide resistant blackgrass hits growers where it hurts. And the effect of reducing net margins is very sensitive to both crop yield and cereal price, warned ADAS David Harris.

A study commissioned by HRAC – the Herbicide Resistance Action Committee – reveals the true cost of controlling resistant blackgrass based on farmer experience at Peldon in Essex, the home of resistant blackgrass.

The calculations use 1997 harvest results and standard financial data for individual cultivations.

The extra costs of annual ploughing, a 7% yield loss associated with delaying drilling and two extra herbicide doses add £194/ha for a 10t/ha wheat crop sold for £100/t.

And the cost of resistance is even greater with grain prices where they are today.

If prices slide to £70/t on the back of Agenda 2000, its important to prevent resistance now, stressed Mr Harris. But the big unanswered question is the propensity of a given population to develop resistance to herbicides.

Scientists are excelling themselves in seeking solutions to your weed control problems, as the Crops team found at this years Brighton Crop Protection Conference.

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