ARABLE farmers will need to face up to the challenge that the loss of important chemicals will place on their businesses – in industry terms, the added cost and crop losses could add up to many millions of pounds.

It looks likely that very few crops will come out of the next couple of years unaffected by the loss of chemical protection, whether it be herbicide, fungicide, or pesticide and the sad fact is that alternatives will be more costly and, likely, not as effective.

So, what can growers do to mitigate against this? In this special feature, SRUC’s Professor Fiona Burnett and Dr Andy Evans, for the Farm Advisory Service, put the microscope on just how much affected growers will be given these changes ...

'Concerns over pesticide losses comes out repeatedly as one of the industry’s main issues when it comes to managing plant health issues going forward.

Vegetable and soft fruit production are particularly at risk because of the limited number of existing actives and the high risks posed by pests and diseases. Alternatives, such as increased use of physical barriers, nets and biological agents will be costly, but necessary for the industry to pick up quickly, alongside enhanced methods of monitoring and predicting pest and disease risk so that sprays can be targeted to maximise effectiveness and profit.

Losses in broad-acre crops also pose concerns and in cereals, the scheduled withdrawal of chlorothalonil in May, 2020, coupled with the potential withdrawal of at-risk azole fungicides would make the management of diseases such as septoria leaf blotch on Scottish winter wheat crops harder.

Looking at some of the actives most used in Scotland, it has been estimated that the withdrawal of prothioconazole alone would reduce the annual £120m Scottish total value of output of winter wheat by 2%, or £2.4m. The additional withdrawal of chlorothalonil would add another 2% reduction, again reducing the value of Scottish wheat by a further £2.4m.

Spring barley, worth £274.83m annually, will also be impacted by the withdrawal of prothioconazole, resulting in a possible £2.74m reduction in value if alternatives, such as new actives and more resistant varieties, are not picked up.

The withdrawal of the insecticide chlorpyrifos, in 2016, has already raised the risk of leatherjacket damage in spring barley, potentially taking 0.5% (£1.37m) off the Scottish crop’s value.

There are currently no pesticide options available to manage this pest, growers having to rely on techniques such as rolling the crop. Due to the revocation of the neonicotinoid cereal seed treatments at the end of 2018, there will be a predicted increase in the use of pyrethroid insecticides to manage aphids and barley yellow dwarf virus (BYDV).

The potential withdrawal of lambda-cyhalothrin (which is at medium risk of withdrawal) and other pyrethroid insecticides, coupled with limited alternatives, could see a resurgence of BYDV and significant yield losses. Those are estimated to be in the region of 1%, or £0.47m for winter barley, £1.2m for winter wheat, and £2.75m for spring barley – particularly in light of grain aphid resistance to pyrethroids.

The recent reprieve of metaldehyde from its previously proposed withdrawal in 2020 is only likely to be temporary and it is probable that this molluscicide will be lost in the next year or two. The withdrawal of metaldehyde is mitigated by the availability of ferric phosphate as a straight (if not more expensive) alternative.

Whilst some herbicides used in cereals are at high or medium risk of withdrawal, there are several alternatives available and economic impact on cereals is likely to be minimal.

Alternatives include new fungicides such as Inatreq and Revysol, plus the increased use of biologicals will, though, add cost and require better ways of predicting pest and disease risk so that usage can be more targeted than currently.

That means that more robust varietal resistance is a key strategy in reducing reliance on pesticides and the acreages planted to more resistant varieties of cereals continues to increase which is a positive.

More use going forward of integrated pest management techniques (IPM) is, therefore, crucial and should be supported by advice and training.'