Underground water system; we know a lot (and a lot we don’t)

Ines van Marrewijk of Groen Agro Control likes to get to the bottom of unusual questions from growers. If there is a solution to a grower’s problem, Ines knows where to find it.

Bacteria unknown

The search for the right methods to measure bacteria in the water requires attention. “Are you looking for a specific pathogenic species such as Agrobacterium or for generally occurring bacteria?” explains Ines. “For example, it could be growth of anaerobic bacteria at low oxygen levels. This is not often tested and should be specifically asked for. Anaerobic and aerobic bacteria surround themselves with a layer of slime that causes biofilm in pipes, among other things. The addition of cleaning agents prevents most biofilm in the pipes themselves. But in dead ends, couplings or rough parts, fouling and germs often remain persistent.  A change of composition in water can sometimes cause the growth of bacteria and also yeasts to suddenly ‘explode’.”

What exactly that is for bacteria is often not immediately clear. “An example: For many years, Groen Agro Control named certain root growth ‘beaded roots’ and yet another image ‘thick roots’. Both appear to have a bacterial cause. It is not yet known that many bacteria can be harmful to plant and/or root growth. We now know more, but by no means everything. The bacterium Ralstonia was also such an ‘unknown factor’ when it suddenly turned up in roses and anthurium, which had not previously been described as a disease in those crops worldwide.”

DNA sequence

One of the advantages that Groen Agro Control has recently acquired to give the identification of bacteria a boost is the new technique of Next Generation Sequencing. By means of DNA sequencing, different variants within a virus, bacteria or fungus can be distinguished. In this way, different genetic variants of viruses, for example, can be better monitored. “Or we can do quality control on microbiological products. This way you can check that the product only contains what it should. The genetic information from drain water or roots can be used to map the microbiological composition. Both beneficial and harmful bacteria, fungi and viruses are detected.

By using sequencing in this way, you don’t focus on just one organism, but immediately see ‘all the micros’ in such a sample. “That sequencing machine has initially been purchased for virus research, after which we will see what has priority. For each purpose, the method will first have to be validated so that high-quality results are obtained from practical samples.”

Solving problems

At Groen Agro Control, the focus with micro is on monitoring cultivation and also on solving problems in the sector. For example, we prevent growth problems in cultivation and at growers through regular analysis of the water. “If you measure a few hundred thousand bacteria per millilitre in ‘clean water’ via germination numbers, that is really too much, certainly for cuttings and seedlings. Then the bacteria get in the way of good rooting, possibly resulting in growth damage.”

Improving resilience is also a key to better water that the company holds. “The magic word ‘resilient’ in analyses requires looking at both good and harmful micros.  With more extensive germ counts, you not only get to see the general fungi and bacteria in the water, but also the germ counts of plant diseases and, if desired, of benign fungi in package ‘Germ Count Resilient’.

“We then look not only at pathogens but also at antagonists – fungi and bacteria that help plants rather than hinder them, such as Trichoderma. You have to do such measurements at a certain frequency to get a good picture of the situation on a farm. As with a UV disinfector, it is not a question of measuring once, you have to keep monitoring.”

Water and ToBRFV

Finally, Ines zooms in on the connection between water and ToBRFV or other water-borne viruses.  According to her, this is still quite a blind spot on farms, mainly because of the complex water system. In principle, water is not the most dangerous factor in the spread of the dreaded tomato virus. During cultivation, the most dangerous factor is juice-on-juice spread. “But during the crop rotation, the risk of water and the drain water system is much higher. You often have to make a 500% effort in hygiene to get 99% results in virus free. Unfortunately, you sometimes only know whether you have succeeded in removing 100% of the virus after it turns out that the new crop remains clean.”

Hygiene and the establishment of protocols is a specialism of Groen Agro Control and Ines also accompanies growers on the farm because hygiene remains customised work.

For more information: Ines van Marrewijk, productmanager bij Groen Agro Control, Distributieweg 1 – 2645 EG Delfgauw, phone 015 2572511

Publication date:
Author: Annet Breure
© GroentenNieuws.nl


First step in lowering MRL overshoot is understanding the whole process

Every fruit and vegetable trader has to deal with it at some point, some more than others: the exceeding of the permitted MRL value on fruit and vegetables and this leads irrevocably to the destruction of the product. Exceeding the MRL often has various causes. Michel Witmer, product manager for foodstuffs at Groen Agro Control, therefore gives the advice to his clients in the AGF to draw up a top five list of products with which they have the most problems. “From that point, they can start working towards improvement and thus fewer MRL violations on fruit and vegetables, thus limiting recalls.”

For 25 years, Groen Agro Control has had a specialised laboratory for analysing chemical and microbiological constituents on fruit and vegetables. “Based on those analyses, we as a company can also give advice on how things can be done differently. After all, many factors play a role when it comes to an MRL violation: When did pesticides end up in the fruit? During cultivation, after harvest or during transport in the container and do the various parties communicate with each other about the permitted value for the end customer? It also happens that such pesticides are sometimes applied by accident. Think of a grower who uses water from the river downstream that has been polluted by another grower upstream.”

Talking to the grower

Michel ziet vooral dat overzees fruit uit Afrika, Zuid-Amerika en Azië soms een te hoog pesticiden gehalte hebben. “Het is daar soms moeilijker om goed contact te houden met de telers die producten verbouwen voor de Europese markt. Zeker als hier in Europa de regels weer veranderen met nog strengere eisen rond de MRL in producten. Neem als voorbeeld straks het nieuwe Pomelo-seizoen. Daarvoor zijn de regels weer veranderd voor gebruik van Chloorpyrifos, maar of een Chinese teler dan gelijk zijn manier van telen gaat aanpassen is maar de vraag. Of wat dacht je van een voorbeeld dichter bij huis: Chloorprofam in aardappelen en uien waarvan het gebruik sinds dit jaar verboden is in de EU.”


Michel says that Groen Agro Control can give advice on adjusting the programmes. “We look for instance at the use of alternatives in crop protection products and the application at a certain moment in the cultivation. In addition, we often see that different pesticides are used on one product with exactly the same effect. We see that happen a lot on strawberries. The biggest gain for many AGF importers is to pass on MRL changes to their suppliers in time.

“The MRL is a fixed maximum value that is set for the use of certain pesticides and the legislation seems to become stricter every year. The European Commission often announces a further tightening six months in advance, giving growers the chance to reduce their doses or look for alternatives. However, the retail sector in Europe applies even stricter requirements on these residues and these also differ per chain. For us, the work would be easier if the retail sector were more transparent about their specifications so we can better inform the sector and the laboratories about the steps to take.

For more information please contact Michel Witmer, product manager at Groen Agro Control, Distributieweg 1 – 2645 EG Delfgauw, phone 015 2572511

Date of publication: Thu 3 sep 2020
Author: Thom Dobbelaar
© AGF.nl

Photography: Martin van der Marel

Groen Agro Control puts focus on compost analyses

Flexible scope for accredited analyses of pesticides in fresh produce and grain

After a positive assessment study by the Dutch Accreditation Council (RvA), the residue laboratory of Groen Agro Control has obtained a flexible scope for the analysis of residues of pesticides in food, animal feed, products derived of plants and water.

Starting from today, the following pesticide residues are also measured under accreditation:

Residue Screening LC-MSMS in Fresh Produce: Bensulfuron-methyl, Dimethirimol, Etoxazole, Fenbutatin Oxide, Buturon, Flupyridafurone, Isouron, Oxasulfuron, Quinoclamine, Terbuthylazine

Polar pesticides in Fresh produce and Grain: Ethephon, Fosetyl, Phosphorous acid, AMPA, Glyphosate, Glufosinate

The new analysis lists for fruit and vegetables and grain are available on our website, the newly accredited substances are also marked with a Q.

ARfD – calculation according to the EFSA PRIMo model version 3.1

Since the 12th of October 2020, Groen Agro Control calculates and reports the ARfD percentage (ARfD value) for the Netherlands with the EFSA PRIMo model 3.1. The Acute Reference Dose (ARfD) is an estimate of the amount of a pesticide in food that a person can ingest within 24 hours without significant health effects. The depletion of the ARfD value is always given as a percentage of the ARfD value.

Previously, the national models were used to calculate the ARfD percentage, in the Netherlands the NESTI model. Recently, the calculation method of the ARfD percentage has been harmonized within the European Union. The calculation model within the European Union is the EFSA PRIMo model (current version 3.1). For the Netherlands, RIVM has also published a list of associated processing factors that are included in the calculation. The calculation of the ARfD with the PRIMo model with processing factors is also used when testing against the requirements of Dutch retailers. For other countries within the EU, the PRIMo model is used without the processing factors.

If you have any questions about this change in the method for the ARfD calculation, please contact your account manager or our specialists from the Pesticide residue laboratory.


Groen Agro Control Peru SAC will attend the 2020 Expoalimentaria trade show

Groen Agro Control Perú SAC is participating in this new version of 2020 Expoalimentaria trade show: Virtual Expoalimentaria from September 30th to November 15th

Virtual Expoalimentaria is a commercial platform which has been created in order to display and promote important products within the food, beverage, machinery, services, containers and packaging sectors for the food industry. It will be used as meeting point for the key operators of distribution, retail, catering industry and specialized channel in the Peruvian and international market.

Be free to visit us and know more of our services: https://join.expoalimentariaperu.com/en or contact by email info@agrocontrol.pe for any request.

Groen Agro Control Peru obtained accreditation for the analysis of residues of crop protection products

Our colleagues in Lima have been working on the validation of the analysis methods for residues of pesticides. The Dutch Board of Accreditation (RvA) recently evaluated these efforts and awarded accreditation to our methods of analysis. Starting from the 7th of September the residue analyses on fruit and vegetables and grains that are carried out by our laboratory in Peru are performed under this accreditation.

If you wish to use the analyses of Groen Agro Control Peru, please contact us via info@agrocontrol.nl

MRL reduction to 0.01 mg/kg for Chlorpyrifos and Chlorpyrifos-methyl from the 13th of November 2020.

On July 23rd , the EU published a correction to regulation EC 2020/1085. This regulation stated that the MRLs for Chlorpyrifos and Chlorpyrifos-methyl will be reduced to 0,01 mg/kg starting from the 6th of August 2020. This date has now been postponed to the 13th of November 2020. This correction can be downloaded from:


The EU authorization for the use of the insecticide Chlorpyrifos has been withdrawn since 1 January 2020. Following this, the MRLs are now also reduced to 0.01 mg/kg.

This MRL reduction may have consequences for importers of many different products but especially for importers of bananas and citrus fruits. Both Chlorpyrifos and Chlorpyrifos-methyl are analysed in the Multi-Residue screening GC-MSMS & LC-MSMS.

If you would like to know what this MRL reduction means for your products, please contact us at info@agrocontrol.nl.

Changes in EU – legislation for residues of Chlorate and Perchlorate

The Analysis of Chlorate and Perchlorate

For both Chlorate and Perchlorate, changes in EU legislation have recently been published.

Maximum residue limits will apply for Chlorate from the 28th of June.

In Europe, the use of chlorate as a plant protection product has been banned for a number of years. In addition to this direct application as a plant protection product, chlorate can also occur in water as degradation products of disinfectants. If this water is used as irrigation during cultivation of crops, there is a chance that the final product contains too much chlorate. The MRLs in potatoes, vegetables, fruit and other foods varies between 0.05 and 0.7 mg / kg of product. The MRLs are set in regulation EC 749/2020 and are effective from the 28th of June 2020.

Maximum levels for Perchlorate in fruit and vegetables, tea, baby food and cereals from the 1st of July.

Perchlorate is one of the contaminants that can get into food. This chemical compound occurs naturally in our environment, but even more because it is a degradation product of fertilizers or disinfectants. Crops can absorb Perchlorate which can result in the contamination of fruits and vegetables with Perchlorate. Long-term consumption of products with perchlorate can cause health risks. That is why the EU has decided to include the levels of Perchlorate in certain products in Regulation EC 1881/2006. From the 1st of July 2020, these maximum levels will apply to the product groups: fruit and vegetables, tea, baby food and processed cereal-based foods.


Perchlorate MRL (mg/kg)
Fruit and vegetables excluding

Cucurbitaceae and Kale

—Leafy vegetables and Herbs




Tea (Camellia sinensis), dried

Herbal and fruit teas, dried

Infant formulas, follow-on formulas, nutrition for

medical use for infants and young children and toddler food (*)

Baby food

Processed cereal-based foods





(*) Preschool food includes milk-based drinks and similar protein-based products for toddlers. These products fall outside the scope of Regulation (EU) No 609/2013

The Residulab of Groen Agro Control can examine your products for Chlorate and Perchlorate residues. For this we have an in-house LC-MSMS method with 0.01 mg/kg as reporting limit. For more information about Perchlorate or Chlorate and the analysis for these residues, please contact us. The MRLs for specific products can also be found in the EU pesticide database (Chlorate) or in the appendix of regulations EC 749/2020 or EC 1881/2006.

The laboratories of Groen Agro Control are fully operational

Because the majority of our analyses are carried out in the context of food safety, we are an important part of the food sector. This is why it is very important that our 3 laboratories are fully operational. In this hectic period, the specialists at our laboratories are busy with the analysis of your samples.

For more information, please contact one of our product managers at info@agrocontrol.nl