Purpose: This work evaluated the efficacy of ultraviolet (UV)-C light on pathogen risk reduction from surface water used for irrigation of cantaloupes in an agricultural setting.
Methods: Replicated cantaloupe plots (12 plots, 3/treatment, plot size 5’ by 15’, 10 plants/plot) were irrigated (spray or drip irrigation) with UV-C light treated or non-treated water. A mixture of pond and well water (1000 L) (UV transmittance rate 53.74±2.12) collected in a tank was inoculated with a cocktail of generic E. coli (ATCC 23716, 25922 and 11775). The inoculated water (7.4 log MPN/100ml) was then treated with UV-C light (16 to 120 mJ/cm2) by passing through a UV-C treatment unit PMD50C1/4.
Results: Significant reduction (P<0.05) of generic E. coli (>4.5 log MPN/100 ml was achieved with lower doses (10 to 20 mJ/cm2) and below the detectable limit of the test for doses above 60 mJ/cm2. The generic E. coli counts on cantaloupe irrigated with UV-C treated or non-treated water were similar (2.57±0.12 and 2.67±0.11 log MPN/cantaloupe). Cantaloupes harvested from drip-irrigated plots were significantly lower in counts (2.72±0.12 log MPN/cantaloupe) as compare to sprinkle irrigated plots (3.97±0.15 log MPN/cantaloupe). Within the drip irrigated treatment plots, cantaloupe harvested next to the drip emitter was higher in counts by at least 1.2 log as compared to cantaloupes far from the drip. In the first trial, a significant die-off of generic E. coli was observed on cantaloupe surfaces within three days from the last day of irrigation; however, levels were similar for five days in the second trial.
Significance: Our results indicated UV-C light as an effective antimicrobial treatment for microbial risk reduction of surface irrigation water, but influence on generic E. coli levels on cantaloupe surface was unclear.