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Reducing residues rises up the priority list

As consumer demand moves inexorably towards pesticide- and residue-free produce, growers, particularly those involved in protected crops, constantly find themselves facing new challenges. Help is at hand and new solutions are being developed to meet those challenges.

As consumer demand moves inexorably towards pesticide- and residue-free produce, growers, particularly those involved in protected crops, constantly find themselves facing new challenges, often as a result of innovation in production methods.  Despite the loss of a number of agrochemicals, help is at hand for growers and new solutions are being developed to meet those challenges.

Changing demand

In the not too distant past those who bought organic produce represented 1% or 2% of consumers and whilst this percentage has increased, organic produce still only represents a small share of the total market.  Perhaps more relevant in the context of commercial production, is the issue of low- or no-residue produce.  Dutch growers now estimate that low- or no-residue (rather than truly “organic”) produce has risen to 20% -25% of the market and they are struggling to satisfy demand.  As a result, prices are being pushed up and there are concerns that if they go too high, demand will start to fall away.

One of the problems in this particular sector, according to Jacco Vooijs, Manager (Food safety) at the Dutch grower cooperative, FresQ, is that national interpretation of European law for organic production varies. For example, in the Netherlands the fact that organic production must be in soil and that grow-bags are not acceptable is discouraging many growers and creating a constraint on potential growth.

“Such differences are really a major issue,” he says, and we need to have a unified European ruling on these, as on other matters.


There is, of course, increasing pressure from major retailers, especially in northern Europe, to reduce pesticide residues to zero.  As the list of approved pesticide products becomes ever more limited in Europe, many retailers are becoming more stringent in their production protocols and encouraging greater use of biological controls.  Such requirements are likely to apply to a number of countries including the UK, Germany and Denmark and suppliers will all be subjected to these new demands.  Problems with illegal residues in sweet peppers from Spain in 2006 only served to highlight the issue further and growers there are concerned to meet the standards required in order to maintain their markets.

In the Netherlands, Jacco Vooijs comments, “We would like to see harmonisation of national registration requirements of crop protection products in general across Europe, to give us a level playing field for production.”  He acknowledges that there are different product requirements in different countries but suggests, “They could at least be harmonised on a regional basis and speeding up this process would be helpful.”

Pest and disease pressures

FresQ growers produce tomatoes, peppers and aubergines to high standards.  In tomatoes in particular, the extension of the production season through use of artificial light in greenhouses has brought its own problems in terms of pest pressures. Planting used to be in December or January and predators were introduced in February to be well established before the arrival of white fly in April or May. The season now starts in September and small white fly populations carried over from the end of the previous season, can build up quickly in the warm, light conditions.  Particular attention needs to be paid to boost predator and parasite populations at this stage, for example using Macrolophus and Diglyphus. The use of beneficial insects as part of an Integrated Pest Management programme can help to achieve effective control consistent with the demands placed on growers by supermarket customers.  In case of population imbalances growers like to have selective chemicals, safe to beneficials, available to help knock down the pest at these times, but say that there are not enough available.

“Oberon (spiromesifen) is ideal for use alongside the biological predators. It is effective against strains of white fly that are resistant to other treatments and also provides control of spider mite,” says Jacco.  “A further much-used option, Applaud (buprofezin), can be used with Encarsia formosa for control of white fly and also has additional activity on scale, mealy bug and leaf hopper pests.”  He goes on to explain, “There are organic fungi like BotaniGard and Mycotal which provide some control by infecting white fly larvae and aphids and are safe for predators but growers must be mindful of the timing of use of other available control products such as pyridaben, abamectin or methomyl carbamate because they knock out the biological predators in the crop.”

“Growers always prefer to use biological predators if they can,” he continues. “They don’t like chemicals for a number of reasons: the time involved in application, the possible effects on the health of workers and the potential for residues on the product, but sometimes their use cannot be avoided.  Something we are concerned about is that the reduction in the number of approved chemicals available means that there are not enough in some cases to allow rotation for resistance strategies.”

Fungal diseases like botrytis and fusarium also present a challenge, especially in organic crops and in a wet year such as 2007 and growers feel that there are few solutions available to them.

Integrated Pest Management

Fortunately however, low- or no-residue production can now be achieved in a variety of crop situations and development work in this area continues to expand the possibilities open to growers.  Biological Crop Protection (BCP), sister company to Certis Europe, has made considerable progress in developing integrated pest control programmes for protected vegetables, soft fruit and ornamentals on a crop by crop, country by country basis, depending on local situations and local registrations.  Programmes are already available for tomatoes and peppers in most Western European countries.


A frequent component of the programmes for protected tomatoes is to start clean before planting the crop, to prevent both disease transfer and insect carry-over, using a disinfectant such as Jet 5. Many growers may also use a chemical such as abamectin to be sure of knocking out any remaining insect pests. Beneficial insects are introduced after planting to prevent infestation, as far as is possible. In France these might include Encarsia formosa, Encarsia with Eretmocerus, Eretmocerus eremicus and Macrolophus caliginosusfor white fly along with Aphidius colemani and Aphidoletes aphidimyza for aphids.  Monitoring is essential so that curative measures, including further introductions of these beneficials and others, can be made.  In the case of high pest pressures, corrective measures may be required using, where possible, biopesticides compatible with the beneficial insects. Again in France, Supreme (acetamiprid), Applaud (buprofezin) and Nissorun (hexythiazox) could be products of choice. In line with the comments made by Jacco Vooijs, availability of such products currently varies from country to country. For example, in the UK the armoury of IPM compatible pesticidesincludes Eradicoat T (maltodextrin), Oberon (spiromesifen), Applaud against the various insect pests and Frupica (mepanipyrim) and Repulse (chlorothalonil) against diseases. The ERII formulation of maltodextrin is available in the Netherlands along with other selective insecticides such as Applaud, Nissorun, Floramite, Turex and BotaniGard. Clean-up solutions at the end of the crop also vary from Oberon in the UK and Netherlands to Supreme in France, which will also be available next year in Netherlands under the name Gazelle.

Spanish tomato growers like Juan Gonzalez Vargas of Motril, Granada find major changes have been necessary in their approach to production and business.

“Everything is changing - the pesticides available, the market regulations, official European guidelines, fruit prices, production costs,” he says. “I have had to adjust my business to all these changes.  However, using beneficials means that I avoid residue problems and in addition I can control some pests that were never controlled before!  Products like Turex are bio-products, compatible with biological controls, to control caterpillars in my crop.”  He adds, “It’s a new way of producing and we have to change our mind-set to cope with the new situation.”


Monitoring for insect pests is important before planting of peppers and sticky traps are used for this purpose.  A similar process to that in tomatoes is followed here with beneficial insects backed up by monitoring, further introductions of predators, biological insecticides and the use of pesticides only where absolutely necessary.  IPM programmes have been developed specific to UK, France, Belgium, Netherlands and Spain with excellent results.  Trials work in a commercial situation has demonstrated a 38% increase on returns for growers using IPM. (see Pepper trials)

Soft fruits

Some of the latest developments are in programmes for soft fruit in UK, Spain and Netherlands and the company is also doing more work in the challenging area of fungal disease control.  In its work with growers BCP is finding that disease problems are reduced where pest management and cultural controls are good.


As the area of protected cropping in UK strawberry production has grown, the use of biological controls has increased and they now provide effective control of major pests such as thrips and spider mite.  However, as with tomatoes in Holland, glasshouse whitefly has become a more problematic pest and in some cases has reached unmanageable infestation levels where even chemicals do not provide effective control.  In one such case BCP developed an IPM programme including Encarsia, Phytoseuilus and predatory mites in combination with selective insecticides and fungicides and results were compared against a conventional programme.

While the costs of integrated control were higher than conventional, these were more than compensated by a dramatic improvement in pest control and higher returns.  Over a three year period crop protection costs did in fact decline by 11% since the adoption of IPM over the whole nursery led to fewer pest outbreaks and reduced need for emergency treatment.  In practice, the more stable ecosystem created also allowed the grower more time to manage the crop as well as increased yield and crop quality.  The reduction in the number of insecticide treatments and the use of more friendly pesticides was particularly pleasing to crop workers and also responds to the demands of the supermarket protocols.

The way forward

Low- or no-residue production is becoming increasingly possible and companies like Certis and BCP are making great progress for the benefit of growers of a variety of protected vegetables, ornamentals and soft fruit across Europe.  Growers must take advice on their own specific situation, based on what is happening in the crop and local registrations but there are certainly a growing number of possible solutions to assist them to meet market requirements and, in some cases, potentially increase profits too. 

Pepper trials

A trials programme conducted in the Almeria region by BCP and the marketing organisation, The Greenery, plus its cooperatives, demonstrates clear benefits offered to growers by IPM.  It set out to compare a conventional chemical-based control programme for peppers with a new IPM strategy combining several biological controls with chemical products selected for their compatibility with beneficial insects.

10 plots were used for the trials: three using conventional chemical-based controls (18,500 m2) and seven using IPM programmes (42,500 m2).  All crops were planted during June and July 2005.

In these trials the IPM programme provided effective pest control using Amblyseius cucumeris, Orius and Nesidiocoris, offering a major advantage of excluding pesticides with high potential residue risks.   Residues were in fact reduced well below maximum limits, thereby allowing growers access to the markets provided by the North European supermarkets.  This benefit alone offers a major impetus for the adoption of IPM in Almeria.

However, this was not the only gain from using IPM.  Yields ranged from 5.3 to 5.8 kg/m2 (average5.5 kg/m2) in the plots using conventional controls and from 5.8 to 6.6 kg/m2 (average 6.19kg/m2) in the IPM plots.  In addition to producing extra yield, the crop was also of higher quality, due to less stress from chemical-based conventional treatments.  As a result a price premium was achieved, increasing returns by 17% from €3.43 (conventional) to €4.03/m2 (IPM).

COST (€/M2)
COST (€/M2)
CONVENT’L 1CONAN5.300.000.983.292.31
CONVENT’L 2BILBO5.800.001.123.712.59
CONVENT’L 3BIPODE5.400.000.923.292.37
CONVENTIONAL AVERAGE5.500.001.013.432.42
IPM 1CONAN6.600.250.304.493.94
IPM 2BILBO6.200.290.434.033.31
IPM 3MELCHOR5.800.410.273.542.86
IPM 4BIPODE6.200.460.284.033.29
IPM 5BILBO6.100.300.383.973.29
IPM 6BISERA6.400.300.374.293.62
IPM 7BILBO6.000.260.443.903.2
IPM AVERAGE6.190.320.354.033.35

The total cost of pest control on the IPM plots (0.68 €/m2) is calculated including the costs of beneficial insects (45% of total cost) plus the low impact insecticides and fungicides (55% of total cost).  The results showed that grower input costs were reduced by 30% under the IPM programme.  Labour costs were not calculated in the project but it is clear that, with fewer treatments needed, labour requirements are lower for IPM than for conventional treatments, so these costs will also be reduced.

The combination of reduced costs of the IPM programme and higher returns for the crop created a substantial overall improvement in grower margins over input costs of 38% as well as meeting the demands of the Northern European supermarkets for reduced residues in the fruit.

Conventional chemical
-based control
IPM control
Pepper price (€/m2)€0.62€0.65
Pepper yield (kg/m2)5.56.2
Crop return (€/m2)€3.43€4.03
Crop protection costs (€/m2)€1.0€0.68
Margin over input costs€2.43€2.43
Percentage improvement over
conventional chemical-based control

The IPM programme tried for strawberries in the UK:

  • Oberon, an effective whitefly clean up, was applied under an off-label approval pre-flowering
  • Predatory mites 1-2 weeks after Oberon
  • Amblyseius cucumeris
  • Amblyseius californicus
  • Hypoaspis miles
  • Phytoseiulus persimilis in hot-spots
  • Encarsia Formosa  from mid-April
  • Eradicoat in pest hot-spots
  • Frupica and Jet 5


Results generated jointly by BCP and strawberry growing Manager Jon Marcar, showed the IPM programme provided effective pest control with an 8% increase in Class 1 fruit, due to a reduction in the fruit damage caused by thrips and a 6% increase in yield compared to the conventional programme.  Even though pest control costs, including necessary labour, were higher, overall returns were 18% higher from the IPM programme and the number of insecticide treatments was reduced from 10 to four.

The table below quantifies the benefit of IPM to the grower, comparing two adjacent blocks in Spring 2005.

Conventional programmeIntegrated programme
Yield2.64 kg/m22.8 kg/m2
Percentage Class 1 fruit75%83%
Pest control costs25p/m236p/m2
Return Class 1 fruit£17.73£20.93
No. insecticide treatments104

     Ongoing work

Further work in this area has continued and new trials have now shown that Encarsia can provide effective control of whitefly at a reduced rate of 1 per m2 weekly, which makes it even more economic.  Where Encarsia was introduced on this basis from mid-April to the end of May, the pest was effectively controlled for the remainder of the crop.  Pymetrozine can also play a role in a cost effective IPM programme.