by Tom Nizet, Bio-Engineer

In August 2024, a group of experts published a guidance document that centralised existing, albeit scattered, knowledge and introduced important new insights for investigating what causes the presence of pesticide residues in organic products. The publication is available as “ A Vade Mecum on Official Investigations in Organic Products.”

Since its publication, the Vade Mecum has been translated into French, Bulgarian, German and Ukrainian, and is available, free of charge, on the following website: www.organic-integrity.org

During Biofach 2026, some of the authors presented case studies that demonstrate the positive impact of the Vade Mecum to guide investigations and to determine “source and cause”, as requested by the EU organic Regulation.

In this article, two of those cases are described and illustrated.

Case 1: Imazamox in organic sunflower cake

Sunflower cake is a by-product from sunflower oil production which may be used as “organic feed”. During two inspections at a processor in Ukraine, a lot of organic sunflower cake was subject to the traceability and mass balance check as well as to sampling by the inspector of the certification body. The laboratory analysis of both samples showed the presence of imazamox in 0,024 and 0,023 mg/kg, a substance not authorized in organic agriculture. After receipt of the laboratory reports, the certification body started the official investigation, and both lots of sunflower cake and sunflower oil produced from the same lot of raw material (sunflower seeds) were provisionally blocked without any delay. The certification body asked the processor to investigate both residue cases and explain the presence of the not authorized substance.

Imazamox is a systemic herbicide. It may be used after sowing to control weeds in fields cultivated with sunflowers. It works against Orobranche cumane, which is a common weed growing in the area where the sunflowers have been cultivated. It’s important to take note that only special hybrids of sunflowers are resistant to imazamox.After an unannounced inspection at the processor, the inspector concluded that neither commingling nor contamination of the batch happened during the processing of the sunflower seeds. The processor only managed organic products since the start of the activity.

The exchange of information between the certification body of the processor and the supplier of the sunflower kernels, showed that the farmer received a derogation for the use of non-organic sunflower kernels. The variety was known as a hybrid from Syngenta, known to be resistant for so called “clear field” technology, which means resistant to imazamox. The sunflower producer explained the need for this variety because neighbouring farmers were applying the clear field technology and there is a lot of drift.

The Vade Mecum contains a list of 17 possible sources for the different residue cases. These 17 sources are the result of the screening of numerous investigations and may be considered as an exhaustive list.

As a first step, the investigators eliminated the irrelevant sources for the specific case, and 5 possible sources have been identified. One of these is a mistake at the level of the laboratory. This has been excluded without further investigation because two samples have been analysed by the same lab.

The aim of the investigation is to collect information which can be used in favour or against each of the relevant (4) possible sources. The overview matrix contained the following information:

Further investigation showed that the farmer did purchase herbicides containing imazamox, but did not show this to the inspector. In addition, documents to justify the purchase of the sunflower seeds had been changed by the farmer, allowing to conclude that the non-organic sunflower seeds had been also treated with non-authorized substances.

The certification body concluded that the source and cause for this case were the intentional use of prohibited substances by the sunflower producer, and downgraded the affected sunflower cake and oil; also the certification body of the supplier confirmed that the lot of sunflowers seeds has been downgraded.

Many thanks to Sergiy Galashevskyy from Organic Standard, Ukraine.

Case 2: Phosphonic acid in organic ginger

This case aimed at identifying the source and cause of one of the most often detected active substances in organic products: phosphonic acid. The particularity of this substance is that it is a so called “multi-source” substance. This means that its presence can be due to a multitude of possible sources, ranging from:

i)                    prohibited use of plant production products with the purpose of stopping fungal infections of plants,

ii)                  historical presence in soil due to use prior to the conversion period,

iii)                the authorised use of non-organic untreated grafting material for perennial crops,

iv)                the unknown (unlabelled) presence of phosphonic acid in fertilisers, either inevitable because of the authorised use of conventional algae or unauthorized because of mixing of compost with unauthorised plant protection products.

On the one hand, the presence of phosphonic acid in organic products may be due to situations that do not represent a violation of the organic production rules, but on the other hand, there are also conventionally produced products which do not contain phosphonic acid. In other words, determination of the source of phosphonic acid in organic products is usually a very complicated activity. Typical amounts vary between 0,03 to 0,10 mg/kg.

Inspired by the Vade Mecum (Chapter 5), the certification body (DE-ÖKO-039) started its investigation by verifying the information received, and concluded that:

i)                    further investigation is relevant because ginger plants are known to be sensitive to fungi attacks,

ii)                  the presence of phosphonic acid is reliable and

iii)                detailed information about the sampling has been documented.

In a second step, the so called “long list” of possible sources has been used to differentiate between the sources which can be immediately excluded and the remaining ones. As a result of this desk analysis, 8 of the 17 possible sources have been excluded.

In a third step, still based on a desk analysis, the certification body has identified indicators which could be used in favour of the remaining possible sources. In the Vade Mecum, the authors also encourage investigators to identify indicators which can be used to reduce the likelihood of one or more of the remaining possible sources.