Dimethoate: A Broad-Spectrum Organophosphate Insecticide

Technical Introduction

Dimethoate (IUPAC: O,O-dimethyl S-[2-(methylamino)-2-oxoethyl] dithiophosphate) is a broad-spectrum organophosphate insecticide and acaricide. It has been widely used in agriculture since the 1960s to control both chewing and sucking insect pests.

• Mode of Action: Dimethoate inhibits acetylcholinesterase (AChE), an essential enzyme in the insect nervous system. This leads to accumulation of acetylcholine, causing continuous nerve impulses, paralysis, and death.

• Systemicity: It is both contact and systemic, moving through plant tissues to protect foliage, stems, and new growth.

• Target Spectrum: Controls a wide range of sap-sucking insects (aphids, thrips, whiteflies, leafhoppers) as well as mites.

Applications

• Field Crops: Used in cotton, wheat, rice, soybean, and maize to manage aphids, leafhoppers, and thrips.

• Vegetables & Fruits: Applied to tomato, potato, citrus, apple, pear, and grape crops for aphid and whitefly control.

• Ornamental Plants: Protects against sap-feeding insects in greenhouses and landscape ornamentals.

• Acaricidal Use: Effective against certain mite species on crops and horticultural plants.

Advantages

• Dual Action: Works as both a contact insecticide and a systemic agent.

• Broad-Spectrum: Effective against numerous insect pests across crop groups.

• Cost-Effective: Relatively low production cost compared to newer insecticides.

• Fast-Acting: Quickly reduces pest pressure after application.

Specifications (Typical Parameters)

FAQ

Q1: Is Dimethoate systemic?
A: Yes, it is both systemic and contact-active, making it effective against pests feeding on internal plant tissues.

Q2: Is Dimethoate safe for pollinators?
A: No. Dimethoate is highly toxic to bees and should not be applied during flowering or when pollinators are active.

Q3: What are the resistance risks with Dimethoate?
A: Resistance has developed in some aphid and whitefly populations due to long-term use. It is recommended to rotate with other insecticide classes (IRAC groups).

Q4: Is Dimethoate still widely used?
A: While still in use in many countries, Dimethoate is restricted or banned in the EU and some other regions due to environmental and human safety concerns.

Q5: How does Dimethoate compare with other organophosphates?
A: It has relatively lower mammalian toxicity than some older organophosphates (like parathion), but its environmental impact remains significant.