Control of Cucumber Downy Mildew through Nighttime Application of Ultraviolet Light Before and After Infection

View the project final report

Commodities

• Vegetables: cucurbits

Practices

• Education and Training: A field day
• Pest Management: Ultraviolet light

Three Northeastern states – NJ, NY and MD - produce about 35 million dollars’ worth of cucumber. Downy mildew (DM) is one of the most significant annual production challenges for cucumber growers in the Northeast region. Prior to 2004, effective DM resistant cucumber varieties were available, but as of 2004 cucurbit DM pathogen strains have overcome the existing resistant varieties and these new strains have caused substantial crop losses in the US. Importantly, the DM causing pathogen (Pseudperonospora cubensis) are known to develop resistance to conventional fungicides. DM produces asexual spores that are wind-born and as a result, the disease becomes widespread. Infected leaves die prematurely resulting in fewer or lower-quality fruits.

We hypothesize that an ultraviolet (UV-C, peak wavelength at 254 nm) dose at night applied before and/or after inoculation will suppress downy mildew in cucumber. A few studies have shown that a pre-inoculation UV dose can induce resistance in the plant and a post-inoculation dose can suppress sporulation of DM. However, the UV-C dose required to control cucumber downy mildew for pre-inoculation and post-inoculation is unknown. Our proposed research will develop dose response functions (amount, duration) for nighttime applications of UV-C before and after inoculation. We will work closely with a regional grower to design a trailer with an adjustable UV-C array that will be attached to a tractor for accurate nighttime dosing. We hypothesize that an optimum UV-C dose would be as effective or more effective than commercially available fungicides for control of cucumber DM in the field.

Growers, extension personnel and researchers will be invited to see the effects of nighttime UV-C treatments for control of cucumber DM during a field day. We will communicate with regional extension personnel on the CCE Vegetable Program Work Teams (PWT) to get the word out on our work, update our Light and Plant Health website (www.lightandplanthealth.org/), present project results at Northeastern regional meetings, focus on developing fact sheets for growers and extension service providers, and publish results in peer-reviewed journals and trade publications. The benefit of the proposed novel approach could result in a cost-effective, alternate disease management strategy that reduces fungicide use, and perhaps, increase cucumber yields.

The project goal is to control cucumber downy mildew in the field using nighttime applications of UV-C. The team will conduct a laboratory study to determine optimum pre- and post-infection doses of UV-C. A trailer suitable for cucumber fields housing UV-C lamps in Northeast will be designed and built to demonstrate the efficacy of pre- and post-infection UV-C applications in the field. We will educate Northeast farmers on the practical application of UV-C treatments.