Is Vector Control Sufficient to Limit Pathogen Spread in Vineyards?

Area of Science:

• Agricultural Entomology
• Plant Pathology
• Epidemiology

Background:

• Vector control is crucial for disease management, but its impact on pathogen spread is often unevaluated.
• Pierce's disease in California vineyards is managed using insecticides targeting the glassy-winged sharpshooter (Homalodisca vitripennis).
• Data linking sharpshooter control to reduced vector pressure and disease spread are limited.

Purpose of the Study:

• To assess the epidemiological value of within-vineyard chemical control of the glassy-winged sharpshooter.
• To determine if imidacloprid application reduces vector pressure and Pierce's disease prevalence.
• To evaluate the long-term effects of insecticide treatment history on disease dynamics.

Main Methods:

• Surveyed 34 vineyards over successive years to monitor vector abundance and disease prevalence.
• Applied systemic insecticide imidacloprid for vector control.
• Analyzed the relationship between insecticide treatment history, vector pressure, and disease prevalence.

Main Results:

• Imidacloprid effectively reduced glassy-winged sharpshooter pressure without significant non-target effects or secondary pest outbreaks.
• Vineyards with a history of regular or intermittent imidacloprid treatment showed lower Pierce's disease prevalence compared to untreated vineyards.
• While treatment history influenced overall disease prevalence, year-to-year changes in disease and pathogen spread were not significantly affected by insecticide treatment or vector abundance.

Conclusions:

• Within-vineyard imidacloprid applications can contribute to reducing pathogen spread, with benefits becoming apparent over multiple seasons.
• The observed modest effect on disease spread may be due to area-wide control efforts reducing regional sharpshooter populations.
• Continued within-vineyard vector control remains important, especially if regional population densities increase.