Phenmedipham: Selective Post-Emergence Herbicide for Broadleaf Weed Control
Technical Introduction
Phenmedipham is a carbamate-class herbicide used primarily for post-emergence control of broadleaf weeds in sugar beet cultivation. It is absorbed mainly through the leaves and acts quickly to disrupt photosynthesis, leading to growth inhibition and necrosis of susceptible weeds.
Mode of Action (MOA): Inhibits photosystem II (PSII) electron transport, blocking photosynthesis and causing accumulation of reactive oxygen species (ROS), which leads to cell membrane destruction.
Selectivity: Sugar beet can tolerate Phenmedipham due to its metabolic ability to detoxify the herbicide.
Formulation: Available as 96% TC, 50% SC, and 50% EC formulations.
Applications
Crops:
Primarily sugar beet, occasionally carrots and onions in certain regions.
Weeds Controlled:
Annual broadleaf weeds: Amaranthus spp., Chenopodium album, Polygonum spp., Stellaria media, Capsella bursa-pastoris.
Application Timing:
Applied post-emergence, usually when weeds are 2–6 leaf stage.
Often applied in 2–3 split doses for optimal control and crop safety.
Advantages
Highly Selective: Safe for sugar beet crops at recommended doses.
Effective Broadleaf Control: Provides quick knockdown of young weeds.
Flexible Use: Can be tank-mixed with other herbicides (e.g., desmedipham, ethofumesate) to broaden spectrum.
Rapid Action: Visible leaf injury appears within 3–5 days, with complete weed death in 7–10 days.
Crop Safety: Minimal impact on crop growth when used as recommended.
Specifications (Typical Parameters)
| Parameter | Description | Typical Value |
|---|---|---|
| Common Name | Phenmedipham | |
| Chemical Class | Carbamate herbicide (PSII inhibitor) | |
| Chemical Formula | C₁₄H₁₆NO₃ | |
| Molecular Weight | ~242.28 g/mol | |
| Appearance | White to light yellow crystalline solid | |
| Purity (TC) | ≥ 96% | |
| Common Formulations | 96% TC, 50% SC, 50% EC | |
| Application Rate | 0.75 – 1.5 kg a.i./ha depending on crop stage | |
| Mode of Action | PSII inhibition → ROS accumulation → cell damage | |
| Persistence | 1–3 weeks in soil depending on conditions | |
| Toxicity | Oral LD₅₀ (rat) > 2,000 mg/kg (low) |
FAQ
Q1: Can Phenmedipham be used in combination with other herbicides?
A: Yes, it is often mixed with desmedipham, ethofumesate, or metamitron to control a broader spectrum of broadleaf weeds in sugar beet.
Q2: Is it safe for all growth stages of sugar beet?
A: Best applied after sugar beet emergence and before the canopy closes. Split applications reduce the risk of crop injury.
Q3: How quickly does it work?
A: Leaf symptoms appear within 3–5 days, and weeds are completely controlled in 7–10 days.
Q4: Does it affect grassy weeds?
A: No, Phenmedipham is selective for broadleaf weeds; grasses require different herbicides.
Q5: Is there a risk of resistance?
A: Some resistance cases have been reported in Amaranthus species; rotation with other MOAs is recommended.
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