First Report of Tar Spot on Corn Caused by Phyllachora maydis in the Great Plains.

Tar spot caused by the fungus Phyllachora maydis Maubl. is a significant foliar disease of corn (Zea mays L.).

Effective Management of Powdery Mildew in Cantaloupe Plants Using Nighttime Applications of UV Light.

Ultraviolet light at wavelengths from 254 to 283 nm/has been reported to effectively suppress powdery mildews in several crops, including some cucurbits. Its use to suppress powdery mildew () specifically in cantaloupe has not been previously reported. We evaluated the foregoing technology in cantaloupe fields for suppression of powdery mildew and possible effects on plant growth and yield.

UV-Transmitting Plastics Reduce Powdery Mildew in Strawberry Tunnel Production.

Strawberry powdery mildew, caused by , can be particularly destructive in glasshouse and plastic tunnel production systems, which generally are constructed of materials that block ultraviolet (UV) solar radiation (about 280 to 400 nm). We compared epidemic progress in replicated plots in open fields and under tunnels constructed of polyethylene, which blocks nearly all solar UV-B, and two formulations of ethylene tetrafluoroethylene (ETFE), one of which contained a UV blocker and another that transmitted nearly 90% of solar UV-B. Disease severity under all plastics was higher than in open-field plots, indicating a generally more favorable environment in containment structures.

Use of Ultraviolet Light to Suppress Powdery Mildew in Strawberry Fruit Production Fields.

We designed and deployed an apparatus to apply UV light for suppression of powdery mildew in open field production of strawberry. The unit was evaluated in a commercial production field for one season, and for two additional seasons in open field research plots at the University of Florida Gulf Coast Research and Education Center. The apparatus contained two 180-cm-long hemicylindrical arrays of twenty 55-W low-pressure discharge UV-C lamps (operated at 30 W; peak wavelength = 254 nm) backed by polished aluminum reflectors covering two adjacent beds of the strawberry planting.

Pulsed Water Mists for Suppression of Strawberry Powdery Mildew.

Powdery mildew () is a destructive and widespread disease of strawberry ( × ), especially when susceptible cultivars are grown in high plastic tunnels or glasshouses. Many powdery mildews thrive in humid environments but free water films on plant surfaces can inhibit conidial germination of some species. We hypothesized that might be directly suppressed by rain through the action of water films and meteoric water.

Effect of Water Stress on Reproduction and Colonization of of Strawberry.

In a number of pathosystems involving the powdery mildews (Erysiphales), plant stress is associated with decreased disease susceptibility and is detrimental to pathogen growth and reproduction. However, in strawberry, anecdotal observations associate severe powdery mildew () with water stress. In a 2017 survey of 42 strawberry growers in Norway and California, 40 growers agreed with a statement that water-stressed strawberry plants were more susceptible to powdery mildew compared with nonstressed plants.