Groen Agro Control wish everyone a Merry Christmas and a successful 2022

Management and staff of Groen Agro Control thank you for the trust and pleasant cooperation in 2021.
We wish you a Merry Christmas and a wonderful, enterprising, inspiring and successful 2022.

Opening hours during this holiday season

In the coming weeks there are a number of holidays on which our laboratory is closed: On December 31 we are open from 8:00 am to 3:00 pm.

Below are the adjusted opening hours and times for the delivery of samples:

  • On Friday 24 December, the priority samples that are present at our laboratory before 10:00 am will be reported on the same day. Other samples will be reported on Monday December 27.
  • On Friday 31 December, the priority samples that are present at our laboratory before 10:00 am will be reported on the same day. Other samples will be reported on Monday 3 January.

Priority analyzes are possible for the multi-residue GC/LC screening, specific analyzes of pesticides and main and trace elements in water.

If you have any questions, do not hesitate and contact us. We are happy to help you

Extension of our BNN recognition for mycotoxins and heavy metals

Groen Agro Control has received extension of BNN recognition. In addition to pesticides (fruit and vegetables, grain, oilseeds and tea), also for mycotoxins and heavy metals. That is why you should contact Groen Agro Control for analyzes on organic products.

We recently received an extension of our BNN certificate. Our laboratory currently meets the requirements set by BNN for the analyzes of residues of pesticides, mycotoxins and heavy metals for biological products in the following groups:
  • fruit and vegetables
  • processed fruit and vegetable products,
  • cereals, grain products, rice, oilseeds and vegetable oils
  • Tea and spices
The Bundesverband Naturkost Naturwaren (BNN) is an organization that safeguards the interests of the organic sector. The quality of BNN-recognized laboratories is guaranteed by strict requirements that they must meet. With the renewed and expanded scope of our BNN recognition, we hope to be able to serve the organic sector even better.

Water-side system in horticulture companies reviewed

This spring, there was little rainwater, so reserves are already being drawn on. In a previous Horticultural Newsmail, Groen Agro Control already drew attention to rules on human pathogens in water according to GlobalGAP. That is about human health. But of course, your crop also requires ‘healthy’ water. “The whole water system is quite complex on many farms. In every pipeline, storage silo or in the unit, or with water treatment via technique or with agents, the water can change and with it the properties on the crop,” says Ines van Marrewijk, product manager at Groen Agro Control.

The focus in microbiology is on monitoring water at a number of places in the system. At the very least, one should regularly check the starting water before and after disinfection and certainly the drip water for germ counts. This can be a limited check on bacteria and fungi alone, but more and more companies are finding it important to have what is known as an ‘Extended Germ Count’ determined, which also shows the lowest possible contamination of Fusarium, Pythium and Phythophthora. And that can be critical for a good assessment of the system, because even though the grower checks and disinfects the water, microbiology can unfortunately multiply again in storage or in the system because a few spores have been left behind.

Sufficient oxygen in water and substrate will be a challenge in summer, with higher temperatures. Measuring is knowing when it comes to oxygen and that can be done very easily with sensors. It is good to realise that as a lab, we normally determine bacteria as aerobic germ count at 300 degrees Celsius. Under anaerobic, i.e. somewhat more oxygen-poor conditions, anaerobic bacteria develop more. If required, we can also count them via anaerobic bacterial count in water. Do this determination additionally and not as a replacement of the aerobic bacterial count. Biological and chemical oxygen consumption as an analysis can also give an impression of the activity in water.

It is often not immediately clear what kind of bacteria it is. “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 appeared in roses and anthuriums; it had not previously been described as a disease in those crops worldwide.”

Don’t just check nutrients in drain water or output water, but also regularly take a sample of the toxic water, is the advice. That way, you can see that the settings and adjustments actually reach the plant. And take a sample of the poison as it reaches the plant or from a day’s supply. Preferably, do not take a sample from the mixing container, not while it is running and certainly not while it is standing still. The mixing of A and B tank with drain water and fresh water is done by pulses and is often not very homogeneous in the mixing tank itself.

Through drift, crop protection agents and even herbicides in the open rainwater basin occur more often than you might think. Therefore, ditch water is sometimes not a safe source. When in doubt, do not only have screening residue done but a more extensive analysis for inhibitors and herbicides.

“We have suitable packages for every type of water. So ask in advance what your goal is so that our lab can use the right analyses. Also take note of the information on sample materials and amount of sample required through our Materials for Sampling page.”

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

Publication date: Tuesday

Uitbreiding capaciteit pathogeen analyses bij Groen Agro Control

Expansion of capacity for pathogen analyzes

Groen Agro Control is further expanding its testing capacity in the field of the pathogens Salmonella spp and Listeria monocytogenes.

This means that even more samples can be used daily and it can be communicated the next day whether the PCR method is positive or negative.

Positive PCR samples have a further confirmation step, but otherwise the customer may receive a report stating absent in 25 grams of product.

Companies within the fresh produce and food industry that have large numbers of samples for these pathogens, and also want a fast service, can contact our colleague Michel Witmer.

Analysis Karanjin

In response to recent demand from major supermarket chains and consolidators, we have introduced the active ingredient Karanjin into our multi-residue screening.

There is currently no authorisation of Karanjin in the EU, so an MRL of 0.01 mg/kg is applied. Because there is a lot of attention for Karanjin, we have set up a method and can now analyse it with the GC-MSMS method. From this week on, we will analyse Karanjin in the screening method. Here is some more information about the method and component.


Regarding the legal status, the active substance is currently not registered as a pesticide in the EU. Therefore, the application of a default MRL of 0.01 mg/kg would be acceptable.
The legal evaluation of the active substance in organic farming also raised questions, as e.g. the use of plant extracts (as foliar fertilisers or plant enhancers) is in principle allowed in organic farming.
With regard to toxicological evaluation, there is currently no known ARfD or ADI (Acceptable Daily Intake) value against which the values obtained in case of detection can be assessed.
However, the fact that the origin, biological or chemical, cannot be distinguished has led the distribution chains, as in the case of Matrine, to decide to prevent the importation of fruit and vegetables containing residues of this active substance in order to protect consumers, while the legal situation is being clarified.

What is Karanjin?

Karanjin is a furanoflavonol, a kind of flavonoid. Flavonoids are a broad group of nitrogen-free organic compounds that are widespread in the plant kingdom. It is obtained from the seeds of the karanja tree, a tree that grows wild in India. Karanjin is an acaricide (against ticks and mites) and also a general insecticide. The effect of this substance in the soil is that it reduces the conversion of Ammonium to Nitrate.

This substance can now also be analysed by Groen Agro Control and is included in the multi-residue screening LC-MSMS and GC-MSMS.

Do you want to check your product for Karanjin or other harmful substances?
Please contact us and consult our colleague Michel Witmer.


Ethylene oxide analysis

Do you need Ethylene Oxide analysis urgently?
Report within a few days possible, ask for the conditions.

The analysis of Ethylene Oxide in sesame seeds

In recent months there have been several batches of contaminated sesame seeds found in the EU with India as country of origin. In these batches, an increased level of Ethylene Oxide was found. In India, Ethylene Oxide is used as a disinfectant on sesame seed. The use of Ethylene Oxide is not permitted in the EU and this substance has an MRL of 0.05 mg/kg for sesame seeds.

Mid October 2020, a recall action of contaminated sesame seed lots was started by the NVWA. This has created a strong demand in the recent period for the analysis of Ethylene Oxide in sesame seeds and products containing sesame seeds.

During the first weeks, our residue lab was flooded with samples of sesame seeds or products in which sesame seeds are processed (oil or crackers). Initially, this analysis was outsourced to one of our partner laboratories, but due to the long waiting time (up to 5 weeks), we set up this analysis ourselves.

After two weeks, the validation process was completed and we started analysing for the customers. Initially with an LOQ of 0.02 mg/kg of product. By further optimisation of this analysis we can now also achieve an LOQ of 0.01 mg/kg. This means that we can now also support the biological sector with this analysis. Our method is also suitable for other products like cereals.

Want to check your product for ethylene oxide or other harmful substances?
Please contact us and discuss with our colleague Michel Witmer.

Groen Agro Control joins Normec Group

Over the past 25 years Groen Agro Control has built a fine company that supports clients with analyses and advice. In order to ensure continuity and growth of our company, we have chosen to join the Normec Group as from March 2nd 2021. We are pleased to have been able to take this step in order to embark on new developments together.

The Normec Group is a Dutch company with similar core values that offers a total package in the field of quality testing, analyses, safety and inspections throughout the food sector. By becoming part of the Normec Group we are able to offer excellent services and high-quality expertise in the agro and food sector.

We’d like to point out that nothing will change for you as our customer. You can continue to count on the same expertise, quality and personal service and you will keep the same contact persons at Groen Agro Control. We are convinced that by joining the Normec Group we are able to offer even better services.

We place great value on personal contact and clear communication. If there are any further questions, we are always available for further assistance.

Kind regards,
Bert van Tol

Contact people for your sector are:
Horticulture and grower associations – Ines van Marrewijk
Fruit and vegetable Trade and Food Industry – Michel Witmer
Arable farming and grassland – Joke de Geus
Peru – Andrea Pro
Other countries – Han van der Put

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


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

Photography: Martin van der Marel

Groen Agro Control puts focus on compost analyses

This week Groen Agro Control received the green light from the Council for Accreditation to perform analyses on organic waste streams such as compost, organic waste, green waste and sewage sludge. The laboratory received the accreditation to perform analyses on nutrients and heavy metals in products that are useful for the soil and have to comply with laws and regulations. These analyses are carried out at our laboratory in Delfgauw. Composting companies and producers of organic waste streams take samples themselves or can have them taken for a fee by Groen Agro Control or through Van de Meerakker Service BV.

Accreditation is the degree of purity of analyses issued by the Council for Accreditation to ensure that customers can blindly trust that the quality of the analyses is in order. To prevent the application of products to the soil from leading to contamination or exceeding legally permitted levels of nitrogen and phosphate, composters have them analysed first. The levels can be passed on to the Rijksdienst voor Ondernemend Nederland (RVO) at their request. This way, the product is registered and the sale takes place in a responsible way.

Groen Agro Control is investing in these analyses because they believe that circular agriculture is the future.  Compost has good properties as a soil improver. An additional advantage is that the quantities of nitrogen and phosphate in compost count for half the application norms that apply to the use of fertilisers in agriculture.

Not all waste streams qualify as soil improvers. Some waste products could pose a danger due to high concentrations of undesirable compounds. In addition to the analyses they perform for composting facilities, they also assist organisations that want to have their waste products tested in order to be approved as usable raw materials for agricultural applications.

More information about the accreditation of compost analyses can be found on our website.

You can also contact Joke de Geus, product manager agriculture and grassland. Or call +31(0)15 257 25 11