During an invasion of boxwood borer in August 2014, I was recommended this product which is commonly used in agriculture in citrus, strawberry and other crops.

The product is effective as it strikes the insect larvae before they do any damage and has eliminated all the green worms with webs that have attacked my boxwood hedge. However, it is essential to spray the product at the start of the attack as the Pyralid multiplies and in about a week can cause enough damage to dry out the leaves and kill the boxwood.

Frankly, after reading up on the subject, I should have used a less environmentally aggressive product and a pyrethroid would have sufficed.

Now we will have to wait until next spring 2015 to see if the affected hedge is finally dead. I will post the conclusion here.

Conclusion : a pyrethroid is enough

Reldan™ 22  

What it is used for and where

Reldan™ 22 (Chlorpyrifos-methyl) Insecticide, broad-spectrum pesticide that acts by contact, ingestion and asphyxiation to control the main pests of apple, pear, peach, citrus, grapevine, tomato, pepper, strawberry, ornamentals, flowers and some minor crops.

Clorpyrifos-metil is a chemical compound, a synthetic inhibitor of organophosphate acetylcholinesterase 

and the name defines the structure of the molecule:

• Chlorpyrifos consists of a phosphorus atom bonded to four other groups: a chlorine atom, a carbon atom of a methyl group and two oxygen atoms, each of which is double bonded to the phosphorus and single bonded to a carbon atom of a trichloroethyl group (CCl3).
• methyl refers to the methyl group bonded to the phosphorus atom.

It occurs as a white crystalline powder and has an ammonia-like odour.

What it is used for and where

Chemical pesticide that attacks insect larvae. It is quite volatile and attaches best to the soil where it performs its function while resisting water well.

Insecticide and acaricide, used against :

• Beetles
• Diptera
• Cereal Lepidoptera
• Homoptera
• Anopheles Gambiae (The mosquito that carries malaria)
• Muscidae (a family of flies)

It is used to protect crops of :

• cotton
• strawberry
• cane fruit
• apple
• pepper
• pear tree
• peach tree
• tomato
• rice
• tea
• vegetables
• vines

Alternatives

Recently many products have been placed on the market that have the same protective target based on the bacterium Gram-positive Bacillus thuringiensis. 

See      Bacillus thuringiensis

Review : Better than Reldan™ 22

Safety

In 2020, the European Union banned the use of Chlorpyrifos and revoked the marketing authorisations due to risks associated with human health such as neurotoxicity, especially to children, and the environment.

Italy. In 2020, the Italian Ministry of Health authorised the use of Chlorpyrifos in grape cultivations for 120 days as a maximum period due to the invasion of the Asian fruit bug and the leafhopper (Scaphoideus titanus) also known as 'flavescence dorée' present in grapevines and apple orchards especially in Veneto (Valdobbiadene and Valpolicella). In 2023, however, it appears that, at least in limited quantities, Chlorpyrifos will be sprayed to prevent crop damage.

Canada. A ban on the use of Chlorpyrifos for most agricultural uses, with the exception of mosquito control, came into effect in 2020.

Brazil. Ban on the use of Clorpyrifos in most agricultural crops.

Chemical synthesis process, simplified version:

• Identification of the raw materials and reagents required for the synthesis of Reldan 22.
• Preparation of the raw materials, which may include organic and inorganic chemical compounds.
• Accurate dosing of the reagents and raw materials according to the specified proportions and conditions for the synthesis of Reldan 22.
• Mixing the raw materials and reagents in a reactive system, such as a chemical reactor, to promote the desired chemical reactions.
• Control of process conditions, such as temperature, pressure, and pH, to ensure that the reactions occur properly.
• Monitoring of the chemical reaction over time to determine the appropriate reaction time.
• Isolation of the desired chemical product, Reldan 22, from the reactive system using separation techniques such as distillation or filtration.
• Purification of the chemical product to remove any impurities or unwanted by-products.
• Characterization of the chemical product through chemical and physical analyses to confirm its identity and assess its quality.
• Packaging of Reldan 22 into suitable containers for distribution and commercialization.

Clorpyrifos-metil studies

Typical commercial product characteristics Chlorpyrifos-methyl

Appearance	White powder
Boiling Point	347.3±52.0°C at 760 mmHg
Melting Point	45.5-46.5°C
Flash Point	163.8±30.7°C
Density	1.6±0.1 g/cm3
Content	≥95.0%
Moisture	≤0.2%
Acidity	≤0.2%
PSA	82.48000
LogP	3.71
Refractive index	1.582
Vapor Pressure	0.0±0.7 mmHg at 25°C
Safety

• Molecular Formula C₇H₇CL₃NO₃PS
• Molecular Weight 322,53
• Exact Mass   320.894989
• CAS : 5598-13-0
• UNII    O49S38267J
• EC Number   227-011-5
• DSSTox Substance ID  DTXSID6032352
• IUPAC  dimethoxy-sulfanylidene-(3,5,6-trichloropyridin-2-yl)oxy-λ⁵-phosphane
• InChI=1S/C7H7Cl3NO3PS/c1-12-15(16,13-2)14-7-5(9)3-4(8)6(10)11-7/h3H,1-2H3 
• InChl Key    HRBKVYFZANMGRE-UHFFFAOYSA-N  
• SMILES   COP(=S)(OC)OC1=NC(=C(C=C1Cl)Cl)Cl
• MDL number  MFCD00055310
• PubChem Substance ID    329756700
• ChEBI  34632
• Beilstein     1541078
• NACRES NA.24  
• RTECS   TG0700000
• UN   3077    2783
• NCI   C163642

Synonyms:

• Chlorpyriphos-methyl
• Trichlormethylfos
• Phosphorothioic acid, O,O-dimethyl O-(3,5,6-trichloro-2-pyridinyl) ester
• Chloropyriphos-methyl
• Caswell No. 179AA
• Methyl chlorpyrifos
• Chlorpyrifos O,O-dimethyl analog
• Reldan™
• Methyl chlorpyriphos

References_____________________________________________________________________

Tarazona, J. V., González-Caballero, M. D. C., Alba-Gonzalez, M. D., Pedraza-Diaz, S., Cañas, A., Dominguez-Morueco, N., ... & Castaño, A. (2022). Improving the Risk Assessment of Pesticides through the Integration of Human Biomonitoring and Food Monitoring Data: A Case Study for Chlorpyrifos. Toxics, 10(6), 313.

Abstract. The risk assessment of pesticide residues in food is a key priority in the area of food safety. Most jurisdictions have implemented pre-marketing authorization processes, which are supported by prospective risk assessments. These prospective assessments estimate the expected residue levels in food combining results from residue trials, resembling the pesticide use patterns, with food consumption patterns, according to internationally agreed procedures. In addition, jurisdictions such as the European Union (EU) have implemented large monitoring programs, measuring actual pesticide residue levels in food, and are supporting large-scale human biomonitoring programs for confirming the actual exposure levels and potential risk for consumers. The organophosphate insecticide chlorpyrifos offers an interesting case study, as in the last decade, its acceptable daily intake (ADI) has been reduced several times following risk assessments by the European Food Safety Authority (EFSA). This process has been linked to significant reductions in the use authorized in the EU, reducing consumers’ exposure progressively, until the final ban in 2020, accompanied by setting all EU maximum residue levels (MRL) in food at the default value of 0.01 mg/kg. We present a comparison of estimates of the consumer’s internal exposure to chlorpyrifos based on the urinary marker 3,5,6-trichloro-2-pyridinol (TCPy), using two sources of monitoring data: monitoring of the food chain from the EU program and biomonitoring of European citizens from the HB4EU project, supported by a literature search. Both methods confirmed a drastic reduction in exposure levels from 2016 onwards. The margin of exposure approach is then used for conducting retrospective risk assessments at different time points, considering the evolution of our understanding of chlorpyrifos toxicity, as well as of exposure levels in EU consumers following the regulatory decisions. Concerns are presented using a color code, and have been identified for almost all studies, particularly for the highest exposed group, but at different levels, reaching the maximum level, red code, for children in Cyprus and Israel. The assessment uncertainties are highlighted and integrated in the identification of levels of concern.

European Food Safety Authority (EFSA); Carrasco Cabrera L, Di Piazza G, Dujardin B, Medina Pastor P. The 2021 European Union report on pesticide residues in food. EFSA J. 2023 Apr 26;21(4):e07939. doi: 10.2903/j.efsa.2023.7939. 

Abstract. Under European Union legislation (Article 32, Regulation (EC) No 396/2005), EFSA is to provide an annual report assessing the pesticide residue levels in foods on the European market. In 2021, 96.1% of the overall 87,863 samples analysed fell below the maximum residue level (MRL), 3.9% exceeded this level, of which 2.5% were non-compliant, i.e. samples exceeding the MRL after accounting for the measurement uncertainty. For the EU-coordinated multiannual control programme subset, 13,845 samples were analysed of which 2.1% exceeded the MRL and 1.3% were non-compliant. To assess acute and chronic risk to consumer health, dietary exposure to pesticide residues was estimated and compared with available health-based guidance values (HBGVs). A new pilot methodology based on probabilistic assessment was introduced to provide the probability of subjects being expose to an exceedance of the HBGV. Recommendations to risk manager are given to increase the effectiveness of European control systems and to ensure a high level of consumer protection throughout the EU.