The importance of pre-harvest interval (PHI) compliance in the export of agricultural products

From January to June 2023, as many as 471 shipments of agricultural products from developing countries to the European Union have been returned due to non-compliance with the maximum permissible limits of toxic residues.

Generally, among farmers in developing countries, there is not much awareness about observing the pre-harvest interval (PHI) during the application of pesticides, which often leads to the return of agricultural products exported from developed countries.

What is pre-harvest interval (PHI)?

PHI is the minimum waiting time, in days, between the last application of a pesticide and when it can be harvested for consumption/market entry. Each pesticide label contains PHI information that varies from product to product. Typically, PHI can range from a day or two to more than 60 days. PHI represents the time sufficient for the target pesticide to break down in a product without leaving residues beyond the maximum permissible residue (MRL). The MRL is the maximum acceptable residue level of a pesticide that is legally tolerated in food and agricultural products during trade. Often measured and expressed in parts per million (ppm or mg/kg). Therefore, compliance with PHI is mandatory and important to comply with MRL.

How does PHI gradually reduce pesticide residues?

for example. This graph shows how the pesticide residues of stamipyrid reach the MRL level in cabbage. Acetamiprid residue reaches 1 ppm from 2.69 ppm in 14 days. Cabbage can be harvested after 14 days.

How is PHI determined?

The first step in determining the PHI for a pesticide is to determine the maximum allowable residue for that pesticide in the product concerned. Extensive studies are then carried out to assess the time (in days) to reduce residues to reach the MRL, considering good agricultural practices (GAP).

The reduction of residue levels for a given pesticide in a crop is influenced by environmental conditions, microbes present on the plant surface and in the soil, rain, sunlight, temperature, etc. Microbial organisms convert pesticide residues into final small molecules such as CO2, water and minerals. It is important to remember that the PHI is not the same for all products for a given pesticide.

Importance of PHI

PHI gives farmers the information needed to ensure that pesticide residues in treated produce do not exceed the MRL. If farmers use two or more pesticides together by mixing them in the sprayer tank, then the pesticide with the longer PHI is more important. Pesticide labels primarily contain information about PHI. If the pest attack is close to harvest and the application of pesticide is needed, of course, pesticides with a short PHI period should be used.