The Addition of Hidden Ingredients in Pesticides and Methods for Their Identification

The practice of adding undisclosed ingredients to pesticides is a persistent challenge in China’s pesticide quality‑supervision system. It not only poses significant risks to the safety and quality of agricultural products but also fosters public skepticism toward the domestic pesticide industry, thereby hindering the high‑quality development of Chinese pesticide enterprises. Consequently, for many years, stringent oversight of such illicit additive practices has remained a key priority and central focus of pesticide regulatory efforts at all levels.

I. What Are Hidden Ingredients in Pesticides?

As the name suggests, “hidden ingredients” are components that exist in a concealed form. They refer to additional pesticide substances inadvertently introduced during the formulation and processing of pesticide products, which are not explicitly listed in the product’s quality standards. These typically include unregistered or unapproved active ingredients, highly active pesticides that have already entered or are about to enter the public domain, highly toxic pesticides that have been banned or restricted by national regulations, and chemical pesticides added to biopesticides.

II. The Hazards of Adding Hidden Ingredients to Pesticides

1. It affects the safety of agricultural products. If the illegally added hidden ingredients are highly toxic pesticides that are banned or restricted, they not only expose applicators to unpredictable risks but may also result in pesticide residues exceeding regulatory limits, posing unacceptable dietary health risks to the population. Moreover, such practices can create significant hazards for China’s agricultural exports to international markets.

2. It poses risks to the ecological environment. Pyrethroid pesticides other than esfenvalerate exhibit extremely high toxicity to aquatic organisms. For example, products such as flufenoxuron and flufenprox—along with cyromazine, diflubenzuron, chlorfluazuron, and triflumuron—demonstrate very high toxicity to crustacean aquatic species like crabs and shrimp. Fipronil poses a high risk to crustacean aquatic organisms and honeybees and degrades slowly in water and soil. Chlorfenapyr is highly toxic to fish, daphnia, and other aquatic organisms, acutely toxic to honeybees, and persists in soil, making it difficult to degrade. All of these active ingredients are prohibited for use on rice; if they are inadvertently included as hidden ingredients in pesticides intended for managing rice diseases, pests, and weeds, they can contaminate water bodies, leading to the death of aquatic species such as fish, crabs, and shrimp.

3. Increases the risk of pesticide resistance. The addition of hidden ingredients to pesticides often results in excellent short-term efficacy; however, long-term use can lead to the repeated application of a single pesticide and alternating use of pesticides with cross‑resistance, thereby increasing pathogen and pest resistance, reducing efficacy, and allowing diseases and pests to proliferate.

4. Increased risk of phytotoxicity. This primarily concerns herbicide products: for example, when 2,4‑D butyl ester is added to atrazine, drift of 2,4‑D butyl ester can easily damage neighboring crops in corn fields, resulting in phytotoxicity. Similarly, active ingredients such as chlorimuron‑ethyl and atrazine may be included as hidden components in herbicides; if the applicator is unaware and subsequently plants sensitive subsequent‑crop species, severe phytotoxicity can occur.

5. Causes poisoning in humans and livestock. Pesticides pose a high risk to humans and livestock during both production and application. When these products contain hidden ingredients that are highly toxic to humans and animals, they can often lead to fatal outcomes. Moreover, due to their concealed nature, once poisoning occurs, it is difficult to administer targeted treatment, resulting in delayed medical intervention and endangering lives. For example, paraquat is frequently added to conventional non‑selective herbicides, and prohibited or restricted organophosphate pesticides are sometimes incorporated into insecticides.

III. Common Cases of Hidden Pesticide Ingredients Added

1. The fertilizer contains hidden pesticide ingredients. Fertilizers are organic, inorganic, microbial, or mixed materials used to supply, maintain, or enhance plant nutrition, as well as the physical and chemical properties of soil and its biological activity, thereby increasing agricultural yields, improving product quality, or enhancing plant stress resistance. Currently, many fertilizers on the market contain plant growth regulators; only those that have been registered, produced, marketed, applied, and regulated in accordance with pesticide laws may be legally sold as agrochemical‑fertilizer products. However, the illegal addition of plant growth regulators during the production and sale of foliar fertilizers is widespread, disrupting market order and posing risks to crop safety. To address this issue, the State Administration for Market Regulation and the National Standardization Administration jointly issued GB/T 37500-2019, “Determination of Plant Growth Regulators in Fertilizers—High‑Performance Liquid Chromatography,” which applies to the quantification of sodium nitrophenolate, 2,4‑D, abscisic acid, chlorpyrifuron, uniconazole, indole‑3‑acetic acid, and indole‑3‑butyric acid in water‑soluble fertilizers, compound fertilizers, complex fertilizers, and blended fertilizers. Any fertilizer found to contain plant growth regulators without proper pesticide registration shall be treated as a counterfeit pesticide.

2. Addition of latent pesticide ingredients to biopesticides. Because biopesticides require fewer submission documents than conventional chemical pesticides, and generally exhibit lower efficacy and slower onset of action, many manufacturers have resorted to adding chemical pesticides to compensate for these shortcomings. The illegal addition of chemical pesticides to biopesticide products—such as matrine, Bacillus thuringiensis, and nucleopolyhedroviruses—is particularly widespread. Commonly detected chemicals include chlorantraniliprole, cyantraniliprole, thiamethoxam, and pyrethroid insecticides; moreover, some unscrupulous producers have even incorporated restricted‑use pesticides like carbofuran and fipronil. Biopesticides are encouraged by national policies due to their low toxicity, reduced risk, and minimal residue levels. However, the illicit incorporation of hidden active ingredients may ostensibly enhance product performance while potentially posing adverse risks to applicators, the environment, and residual contamination.

3. Addition of hidden pesticide ingredients to plant growth regulators The pesticide ingredients commonly added to plant growth regulators are primarily brassinolide, gibberellic acid, sodium nitrophenolate, or fungicides, with the aim of enhancing crop vigor, improving stress resistance, and upgrading the quality of crops and fruits.

4. Addition of hidden ingredients to conventional chemical pesticides. (1) Common hidden ingredients added to insecticides. In terms of product types, the hidden ingredients are predominantly restricted or banned pesticides, such as phorate, isocarbophos, fipronil, endosulfan, carbofuran, and methomyl. From an active‑ingredient perspective, these additives often include highly effective compounds that have recently expired or are about to expire under patent protection, including chlorantraniliprole, spirotetramat, and flonicamid. As for their intended effects, the most frequently added substances are pyrethroid insecticides like cypermethrin and lambda‑cyhalothrin, along with avermectins and emamectin benzoate. (2) Common hidden ingredients in fungicides. Fungicides typically incorporate inexpensive, older‑generation formulations, such as mancozeb, thiram, chlorothalonil, azoxystrobin, pyraclostrobin, prochloraz, tebuconazole, hexaconazole, tricyclazole, and imazalil. (3) Common hidden ingredients in herbicides. Herbicides often contain hidden additives like paraquat, diquat, atrazine, simazine, isooctyl ester of fluoroxypropionic acid, nicosulfuron, atrazine, mesotrione, diflufenican, and 2,4‑D butyl ester. Notably, in non‑selective herbicides—particularly those with poor rapid‑acting performance, such as diquat, glyphosate, and glufosinate—the illegal addition of paraquat, which exhibits strong immediate efficacy, is a particularly serious issue.

IV. Methods for Identifying Hidden Ingredients in Pesticides

1. Identify hidden pesticide ingredients by examining label information. In cases where pesticide manufacturers illegally add other pesticide ingredients or unilaterally expand product efficacy and enhance control performance, it is possible to analyze the motivations behind such illicit practices by examining the active‑ingredient and target‑pest information listed on the pesticide label, in conjunction with the latest developments in pesticide research, development, production, and marketing. This approach can help preliminarily identify potential additional pesticide ingredients that may have been incorporated into the product.

2. Identify the concealed pesticide ingredients added by analyzing the physicochemical properties of the pesticide product. Based on the pesticide product’s appearance (color, odor, physical state) and solubility, its chemical classification is determined to identify any concealed active ingredients, followed by further verification of these hidden components.

3. Testing is performed using analytical instruments. Using instruments such as gas chromatography, liquid chromatography, gas chromatography–mass spectrometry, and liquid chromatography–mass spectrometry, along with relevant analytical methods, preliminary screening is conducted based on retention times and spectral data to identify potential hidden pesticide components in pesticide products.

Source: Pesticide registration agency