Pesticide reduction plan drives French research

When the government decides to cut pesticide use by 50% in 10 years, it tends to focus the mind. That was certainly the case at Les Culturales, the French equivalent of Cereals, where there was a strong emphasis of how French growers could cut their pesticide use.

The goal of the Ecophyto 2018 plan, announced in 2008, was to reduce pesticides by 50% if possible, Nathalie Verjux, head of Arvalis‘s genetic and plant protection department, explained to Farmers Weekly. “It is France’s answer to the European Sustainable Use Directive.”

Within that directive, there is a requirement for each member state to have a national action plan to decrease the risk from pesticides. “But it is the choice of the French government to interpret that as also reducing their use.”

French growers understood the need to reduce pesticide use, particularly with consumer pressure increasing, she said. “But the difficulty is to find new solutions that decrease pesticide use, while not also decreasing production. The government has made it clear that production levels should be maintained or increased.”

Over 100 recommendations in nine core focuses make up the plan, which will cost €200m (£178m) over the 10 years, and is funded by a pesticide tax on French growers. Only recommendations from one focus – about training of farmers, advisers and sellers of pesticides – are compulsory, however, to meet the requirements of the European Directive.

“There has been a free experimental system over the past two years, Certiphyto, which has trained 127,000 farmers and advisers so far. In total, around 800,000 people will need certifying.”

Les CulturalesPesticide use will be monitored by the number of unit doses (NODU) that have been applied, calculated from national sales figures. An average of three seasons from 2008-11 would form the reference period, Mrs Verjux said.

Meeting the 50% reduction target was not possible by 2018, she believed, unless new solutions were found. There was a research budget within Ecophyto 2018, but, as yet, programmes had not been defined.

However, Arvalis, an applied research institute funded by farmers, had already started its own research, along with other institutes such as INRA, into possible methods of reducing dependence on pesticides.

Improved genetics was seen as the best single measure that could be employed – with the possibility of reducing fungicide and insecticide use by 50% in the 10-year period.

“Farmers are asking for crops with more resistance against disease,” said Jean-Paul Prevot, Arvalis area manager for Picardy. “So we are working with INRA to identify genes to focus on, to help breeders select genes using assisted marker selection techniques.”

There could also be changes to the way the French recommend cereal varieties. Currently, much like the UK system, varieties are treated with a high level of fungicides so they can achieve their full genetic potential.

But in future, Mrs Verjux said, there could be a second set of plots treated only with a low level of protection, to find the varieties that produced the highest yields with a reduced amount of pesticides. “That would help take into account a decreasing level of pesticide and allow registration of varieties that respond to both high and low-input systems..”

The system was being tested this season, she said. “In potatoes, they are looking at a slightly different approach, where pesticide use is determined by decision support systems.”

Reducing fungicide inputs

Les Culturales125Growing more resistant varieties could cut wheat fungicide use by up to 0.8 dose units compared with susceptible varieties, Claude Maumene, Arvalis’s fungicide expert, suggested.

Comparisons between Barok, a resistant variety, and Bermuda suggested there was €35/ha difference in the cost of the optimum fungicide dose between the varieties, Mr Maumene said. “One full dose unit of fungicide costs around €45/ha (£31/ha), so that difference is equivalent to about 0.8 of a dose unit.”

More French growers could also tailor fungicide use according to variety, he added. A BASF survey suggested that only 25% of French growers had different programmes for different varieties. “It is easier to manage fungicides according to the most susceptible variety, but that isn’t the best way to save chemicals.”

Arvalis had also been developing a decision support tool, Sepo-Lis, that could help growers target the first timing for septoria control more accurately. Based on rainfall data, the tool predicted the date the first spray should be applied, based on different varieties and drilling dates, Mr Maumene said.

“This year, it suggested delaying spraying until there was rain in late April.”

That could potentially allow growers to reduce fungicides in drier years, but the system didn’t take into account other diseases, he pointed out. “We need to manage all disease together, so we are working on a global system to do that.”

Reducing herbicide use

Cutting herbicide use by 50% would be extremely difficult, particularly with grass weed populations and herbicide resistance increasing, said Ludovic Bonin, Arvalis weed expert.

“The first thing growers should do is to reduce their weed burden through rotation, delayed drilling, increased spring cropping and soil tillage. It is very difficult to reduce herbicides if there is a high level of blackgrass or ryegrass.”

An option Arvalis researchers had considered was introducing mechanical weeding. But it was almost impossible to practically do in wheat, Mr Bonin admitted.

“Successful mechanical weeding depends on soil moisture. You need a dry soil and at least four days with no rain after weeding for it to work well. From mid-November to January, on a soil type with 15% clay that requires five days after rain before it is possible to travel, there are just two days where efficient mechanical weeding could typically take place, according to our model.

“On heavier soils with 20% clay, there are zero days. Right now, mechanical weeding isn’t a solution for winter cereals.”

Plant defence stimulators

A trial testing products that stimulate plant defences suggest their use might allow potato growers to cut fungicide use for blight control, Denis Gaucher, Arvalis’s potato expert, said.

The trial, carried out in Boigneville last year in potatoes inoculated with blight and under high pressure conditions, tested potassium phosphite, which has a little fungicide activity as well as being able to stimulate plant defences.

On its own, it gave some reduction in blight compared with the untreated control at full rate, but not enough to be commercially acceptable.

But when applied with a 50% dose of fungicide, the level of blight that developed over the course of the season was only slightly higher than where a 100% dose of fungicide had been applied, he said.

A second elicitor, Solavit manganese, with the same dose of fungicide, had given slightly better results, he added. “It gives some encouragement that in combination with varietal resistance, decision support systems and cultural controls, it could be possible to reduce blight sprays by 50%.”

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