Shedding the Light on Powdery Mildew: The Use of Optical Irradiation in Management of the Disease.

Ultraviolet (UV) irradiation below 300 nm may control powdery mildew in numerous crops. Depending on disease pressure, wavelength, and crop growth stage, one to three applications of 100-200 J/m2 per week at night are as effective or better than the best fungicides. Higher doses may harm the plants and reduce yields.

Propionate poses antivirulence activity against Botrytis cinerea via regulating its metabolism, infection cushion development and overall pathogenic factors.

Botrytis cinerea is a devastating pathogen causing gray mold in fruits and vegetables if not properly managed. Although the mechanisms remain unclear, we previously revealed that the safe food additive calcium propionate (CP) could suppress gray mold development on grapes. The present study reports that sub-lethal dose of CP (0.

Functional Characterization of Photolyase Reveals Mechanisms Behind the Efficacy of Nighttime UV on Powdery Mildew Suppression.

Powdery mildews can be controlled by brief exposure to ultraviolet (UV) radiation with devastating effect on their developmental stages including conidia germination. The treatment effect can be impaired by subsequent exposure to UV-A/blue light. UV-A/blue light-activated photolyase may be responsible for this and therefore we tested the function of three cryptochrome/photolyase family (CPF)-like genes (OINE01015670_T110144, OINE01000912_T103440, and OINE01005061_T102555) identified in the obligate biotrophic fungus , the cause of tomato powdery mildew.

Wavelength dependent recovery of UV-mediated damage: Tying up the loose ends of optical based powdery mildew management.

Controlled environment chamber experiments at Petri dish level were conducted to examine the wavelength and dose dependent efficacy of ultraviolet (UV) radiation, the recovery action potential of optical radiation applied concomitantly/subsequently to effective UV treatment, and the lapse time between UV treatment and subsequent exposure to recovery wavelength on germination efficiency of Oidium neolycopersici conidia. Conidia of eight- to nine-day-old colonies were dusted on water agar surface in Petri dishes and exposed to UV treatments (without lid). Immediately after UV treatments, Petri dishes were sealed and incubated in darkness or differing optical environments generated using seven different radiation sources (range 290nm to 780nm).

Daily light integral and day light quality: Potentials and pitfalls of nighttime UV treatments on cucumber powdery mildew.

Nighttime ultraviolet (UV) radiation, if applied properly, has a significant potential for management of powdery mildews in many crop species. In this study, the role of growth light duration, irradiance, a combination of both (daily light integral) and light spectral quality (blue or red) on the efficacy of UV treatments against powdery mildew caused by Podosphaera xanthii and the growth performance of cucumber plants was studied in growth chambers. Increasing daily light integral provided by high-pressure sodium lamps (HPS) decreased efficacy of nighttime UV treatments against P.

Suppression of Powdery Mildews by UV-B: Application Frequency and Timing, Dose, Reflectance, and Automation.

Disease-suppressive effects of nighttime applications of ultraviolet-B (UV-B) were investigated at two irradiance levels (1.6 or 0.8 W/m) in strawberry and rosemary plants inoculated with Podosphaera aphanis or Golovinomyces biocellatus, respectively.

Effect of light quality and light-dark cycle on sporulation patterns of the mite pathogenic fungus Neozygites floridana (Neozygitales: Entomophthoromycota), a natural enemy of Tetranychus urticae.

A controlled climatic chamber microcosm experiment was conducted to examine how light affects the hourly sporulation pattern of the beneficial mite pathogenic fungus Neozygites floridana during a 24h cyclus over a period of eight consecutive days. This was done by inoculating two-spotted spider mites (Tetranychus urticae) with N. floridana and placing them on strawberry plants for death and sporulation.

Determination of UV action spectra affecting the infection process of Oidium neolycopersici, the cause of tomato powdery mildew.

Oidium neolycopersici, the cause of powdery mildew in tomato, was exposed to UV radiation from 250 to 400 nm for 1, 12, or 24 min. Radiation ≤ 280 nm strongly reduced conidial germination, hyphal expansion, penetration attempt and infection of O. neolycopersici.

Suppression of Cucumber Powdery Mildew by Supplemental UV-B Radiation in Greenhouses Can be Augmented or Reduced by Background Radiation Quality.

This study demonstrates that the spectral quality of radiation sources applied with ultraviolet-B (UV-B; background radiation) affects the suppression of cucumber powdery mildew (Podosphaera xanthii) by UV-B. Suppression provided by daily UV-B exposure of 1 W/m for 10 min was greatest in the presence of red light or by a complete lack of background light, and powdery mildew suppression was least in the presence of ultraviolet-A (UV-A) or blue radiation compared with plants exposed only to 16 h of daily natural light supplemented with high-pressure sodium lamps that supply broad-spectrum radiation with peaks in the yellow-orange region. Exposure of powdery mildew-inoculated plants to supplemental red light without UV-B, beginning at the end of the daylight period, also reduced disease severity; however, supplemental blue light applied in the same fashion had no effect.

Suppression of Powdery Mildew (Podosphaera pannosa) in Greenhouse Roses by Brief Exposure to Supplemental UV-B radiation.

Ultraviolet (UV)-B (280 to 315 nm) irradiance from 0.1 to 1.2 W m and exposure times from 2 min to 2 h significantly suppressed powdery mildew (Podosphaera pannosa) in pot rose (Rosa × hybrida 'Toril') via reduced spore germination, infection efficiency, disease severity, and sporulation of surviving colonies.

Specific Light-Emitting Diodes Can Suppress Sporulation of Podosphaera pannosa on Greenhouse Roses.

When rose plants bearing colonies of Podosphaera pannosa were placed in a wind tunnel, the number of conidia trapped was directly proportional to intensity of daylight-balanced (white) light from 5 to 150 μmol m s. Illumination of samples using blue (420 to 520 nm) light-emitting diodes (LEDs) increased the number of conidia trapped by a factor of approximately 2.7 over white light but germination of conidia under blue light was reduced by approximately 16.