Compared with 20 years ago when Peter Hall left university, he estimates that pesticide use has fallen by 75% on his Kent orchards.
‘In those days, we were using old fashioned chemical technology,’ said Mr Hall, who farms near Marden in Kent and grows top fruit, hops, a small arable area and some grass.
‘The reduction has levelled off, though. What is happening is that we are using more, different molecules but they are specifically targeted against different pests.’ The only way Mr Hall could reduce pesticide use even more is with further advances in technology such as pheromone mating disruption systems and plant breeding for more resistant varieties such as the Bodicea aphid-resistant hop.
Lettuce grower uses less pesticide on icebergs
Between 1990 and 2003, G’s Marketing, a big fresh produce supplier, has cut the pesticides used on its lettuce crop by about 75%.
‘There were 21 kilograms of active ingredient used per hectare in 1990,’ said Chris Foulds, technical director for G’s, which sells 80% of its produce to supermarkets, including Tesco, Waitrose, Marks and Spencer and Sainsbury’s. ‘By 2003, that was down to five kilograms.’
‘A range of measures are behind the reduction,’ said Mr Foulds. ‘There is no one big step. A lot of care and attention is paid to strategies such as walking the crop, disease and pest forecasting and targeting each application of pesticide to a specific need.’
Treatments are not used until a threshold of pests has built up in a crop. ‘There is very little acceptance by consumers of aphids – even in a whole head crop such as lettuce which customers are supposed to be washing before use.’ This means that seed treatments such as Gaucho (imidacloprid) are used to control aphids within the first 20 to 30 days of lettuces going into a field followed by monitoring and spraying when necessary.
In the UK, G’s is growing on about 1,500 hectares of land for iceberg lettuce, a large area for an intensive horticultural crop. In total, G’s grows 8,332 ha of salad crops and vegetables. For year-round production, crops are grown in the UK during the summer and in Spain during the winter.
There are threshold levels for diseases, too, and if just the outer lettuce leaves are affected, G’s will wait before taking action. In one location, aphids were thriving in Lombardy poplars and affecting the lettuces. So rather than use pesticides, the poplars were replaced with different trees.
G’s has some bio-pesticides in its armoury, but these can work out at more than £1,000 a hectare. ‘We do not have any commercial value back from using bio-pesticides such as Nemaslug and Bt (the soil bacterium
Bacillus thuringiensis).’
The company has tried crop covers and other barriers to keep pests away, but everything has had to be done on a large scale and there was limited success. Timing cultivations to avoid fields with pest infestations has been important. Beetle banks have been used to encourage predators to tackle the pests. ‘But a beneficial insect can be as much of a problem as a pest if it is in a bag of prepared salad,’ Mr Foulds told the conference. ‘I think consumers need a lot of education about this.’
Integrated farming saves the Co-op money
Over eight years, a project run by Farmcare – the farming arm of the Co-op – has reduced pesticide applications by about 50%. Between 1994 and 2002, PROBE – which stands for Profit, Biodiversity and the Environment – has managed to do without some chemicals and improve profits on the integrated farming plots.
‘We have found that we cannot compromise in terms of grass weed control,’ said David Gardner, head of business excellence at Farmcare and responsible for the PROBE project. But some broadleaved weeds can be tolerated.
‘We spray the flag leaf in a very robust fashion but there are many occasions when we manage to drop out a particular fungicide treatment, trace elements, adjuvants and growth regulators.’ During the eight years of PROBE, these and other measures such as varietal resistance or cultural controls have helped to reduce the amount of active ingredient going on to the PROBE integrated farming plots by almost 50%.
The PROBE site is in Leicestershire and the project is sponsored by the Environment Agency, the Royal Society for the Protection of Birds and DEFRA (the Department of the Environment, Food and Rural Affairs). The site totals about 150 acres and contains seven fields, each of which is divided into two plots: one is managed according to integrated practices, and the other follows conventional practices used on the rest of Farmcare’s Stoughton Estate. The soil is a medium to heavy clay loam. There is a rotation involving two years of grass followed by winter wheat, set-aside, winter wheat, a second wheat, oilseed rape and winter wheat.
Broadly speaking, the conventional plots have involved ploughing followed by cultivations and a fairly robust spray programme. On the integrated plots, strategies followed have been: minimal cultivations, direct drilling and a reduced spray package using one fungicide instead of two or three; cutting out growth regulators; and using varietal resistance.
In terms of profitability, PROBE has consistently achieved slightly lower yields on the integrated plots but a higher gross margin. For example, in 2003 one of the winter wheat plots had fixed and variable costs of £613 a hectare on a conventional plot compared with £534 a hectare on the integrated plot. Yet, averaged over eight years, the conventional plots have yielded 7.84 tonnes of wheat a hectare compared with 7.25 tonnes for the integrated plots ‘I think it is a bit more risky,’ Mr Gardner emphasised, ‘but we have managed to deal with those risks over the years .’ The 50% reduction in active ingredient on the integrated part of the experiment has saved money and contributed to better profits.
But Mr Gardner emphasised that this achievement came with a health warning: where direct drilling had been tried, robust grass weed control was absolutely essential. ‘You simply cannot compromise on this,’ Mr Gardner insisted. ‘When we have used direct drilling on the integrated plots, our use of herbicides for grass weed control has sometimes been greater than on the conventional plots.’
Direct drilling has been notoriously unreliable, and the 2003 crop from the integrated plots has suggested that Farmcare must be prepared to use more slug pellets in future. ‘Life is about compromises, and it seems that if you direct drill, you may have to increase the use of slug pellets.’ Direct drilling has the potential to save money but its unreliability would deter many farmers from trying the technique.
Farmcare is aware of research in Australia in which satellite technology is being used to put ‘controlled wheelings’ into the crop. All machines are then multiples of a particular width – eight metres, for example – so that tracks left by wheels are in the same place year after year. Mr Gardner said the workability of the soil would be expected to improve under this kind of regime.
[This article first appeared in Pesticides News No. 64, June 2004, page 6]