news and research about Pierce's Disease

What is Pierce's Disease?

Pierce’s Disease is a bacterial infection, which is spread by bugs that feed on grapevines, particularly the "glassy winged sharpshooter." Grapevines that become infected with PD can quickly become sick and die.

Seasonal population dynamics of homalodisca vitripennis (hemiptera: cicadellidae) in sweet orange trees maintained under continuous deficit irrigation

  • Author(s): Krugner, R; Groves, RL; Johnson, MW; Flores, AP; Hagler, JR; Morse, JG;
  • Abstract: A 2-yr study was conducted in a citrus orchard (Citrus sinensis L. Osbeck cultivar Valencia) to determine the influence of plant water stress on the population dynamics of glassy-winged sharpshooter, Homalodisca vitripennis (German). Experimental treatments included irrigation at 100% of the crop evapotranspiration rate (ETc) and continuous deficit-irrigation regimens at 80 and 60% ETc. Microclimate and plant conditions monitored included temperature and humidity in the tree canopy, leaf surface temperature, water potential, and fruit quality and yield. Glassy-winged sharpshooter population densities and activity were monitored weekly by a combination of visual inspections, beat net sampling, and trapping. Glassy-winged sharpshooter populations were negatively affected by severe plant water stress; however, population densities were not linearly related to decreasing water availability in plants. Citrus trees irrigated at 60% ETc had significantly warmer leaves, lower xylem water potential, and consequently hosted fewer glassy-winged sharpshooter eggs, nymphs, and adults than trees irrigated at 80% ETc. Citrus trees irrigated at 100% ETc hosted similar numbers of glassy-winged sharpshooter stages as trees irrigated at 60% ETc and a lower number of glassy-winged sharpshooter nymphs than the 80% ETc treatment, specifically during the nymphal density peak in mid-April to early July. Irrigation treatments did not affect populations of monitored natural enemies. Although the adult glassy-winged sharpshooter population was reduced, on average, by 50% in trees under severe water stress, the total number of fruit and number of fruit across several fruit grade categories were significantly lower in the 60% ETc than in the 80 and 100% ETc irrigation treatments.
  • Publication Date: Feb 2010
  • Journal: Journal Of Economic Entomology