222 Nm Far-UVC in Crop Protection: Promising, but Not Yet Proven

A new wavelength is being discussed in horticulture, but the commercial evidence is not yet strong enough to declare a winner.

Most commercial UV-C crop-treatment systems use 254 nm lamps. The technology is established, measurement tools are available, and robotic systems are already being tested or used against diseases such as powdery mildew and anthracnose. Against that backdrop, 222 nm far-UVC is attracting attention.

A recent peer-reviewed study compared both wavelengths against 13 fungal isolates representing five Colletotrichum species associated with strawberry anthracnose.

Both wavelengths reduced fungal growth in laboratory tests and anthracnose symptoms on detached strawberry leaves, although the response varied between isolates.

Far-UVC produced strong suppression at lower delivered doses in the laboratory tests.

It also performed similarly with or without a four-hour dark period, while darkness improved the effect of 254 nm.

For growers, that is the most interesting finding.

If confirmed under commercial conditions, far-UVC could widen the treatment window and help one robotic platform cover more hectares.

What the study does not show is whether far-UVC is faster, cheaper or more energy-efficient in commercial use.

The researchers used different lamp systems with different power characteristics, so exposure time alone is not a valid commercial comparison.

The important measures are the dose delivered to the crop, irradiance at the working distance, treatment width, robot speed, biological response, energy use, lamp life and cost per hectare.

Crop safety also needs attention.

Moderate doses of both wavelengths reduced anthracnose symptoms on detached strawberry leaves, but higher doses caused visible injury. A separate laboratory study on Arabidopsis reported stronger surface-cell damage from far-UVC than from 254 nm at the doses tested.

This does not mean the technology is unsuitable for crops. It means the effective dose range may be narrow and crop-specific.

The term “safer far-UVC” usually refers to reduced penetration into human tissue. It should not be interpreted as safe for plants at any dose. Leaves, flowers, pollen and fruit still require testing.

Some systems may also generate ozone, depending on lamp spectrum, filtration and operating conditions. Greenhouse trials therefore need to assess ventilation, worker exposure and crop response.

For now, 254 nm remains the stronger commercial platform. It offers mature lamp technology, established measurement methods and practical field experience.

Far-UVC is not commercially proven, but the evidence is strong enough to justify controlled greenhouse trials, particularly against strawberry anthracnose.

A proper comparison should use intact plants, equal delivered doses, realistic robot speeds and repeated treatments across different canopy positions.

It should measure disease incidence and severity, crop injury, flowering, fruit set, yield, ozone, energy consumption, lamp replacement cost and total cost per hectare.

The future may not be a choice between two wavelengths.

Different crops, pathogens and treatment timings may require different protocols.

At CropTIQ, we are looking forward to seeing how far-UVC develops.

If the early research can be confirmed under real commercial conditions, it could offer growers a significant new advantage and become an important part of more sustainable crop-protection programs.

The current position is clear:

254 nm is commercially ready.

222 nm Far-UVC is scientifically promising.

The next step is proper crop-side validation.

The value of UV-C treatment is not the wavelength printed on the lamp. It is the dose that reaches the crop, the disease response it produces and the commercial result at harvest.

Sources

Smith, B. J. et al. “UVC (254 nm) and Far UVC (222 nm) Irradiation Affects In Vitro Growth of Colletotrichum sp. Isolates and Their Infection of Detached Strawberry Leaves.” PhytoFrontiers, 2024. DOI: 10.1094/PHYTOFR-03-24-0016-R.

USDA Agricultural Research Service publication record on far-UVC treatment of strawberry fungal pathogens, 2021.

Otake, M. et al. “222 nm ultraviolet radiation C causes more severe damage to guard cells and epidermal cells of Arabidopsis plants than does 254 nm ultraviolet radiation C.” Plant Cell Reports, 2021.

National Institute of Standards and Technology. Research on the spectral characteristics and indoor-air effects of 254 nm and far-UVC germicidal devices, 2024.