Biological agents for whitefly control in Sardinian greenhouse tomatoes

Area of Science:

• Horticultural Entomology
• Integrated Pest Management
• Biological Control

Background:

• Whiteflies are significant pests in greenhouse tomato production, causing substantial economic losses.
• Conventional pest control methods often involve broad-spectrum insecticides, which can negatively impact beneficial insects.
• Alternative biocontrol strategies are sought to manage whitefly populations sustainably.

Purpose of the Study:

• To evaluate the efficacy of releasing natural enemies for whitefly biocontrol in greenhouse tomatoes.
• To compare the effectiveness of different release programs and species of beneficial insects.
• To assess the influence of cultural practices and insecticide residues on biocontrol success.

Main Methods:

• Field experiment conducted on 29 greenhouse tomato crops in Sardinia (2005-2006).
• Release of natural enemies: Macrolophus caliginosus, Eretmocerus mundus, and Encarsia formosa at specified densities.
• Monitoring of whitefly and predator populations, species composition, and mortality of immature whiteflies.
• Comparison between biocontrol agent (BCA) greenhouses and control (no BCA) greenhouses.

Main Results:

• Release of M. caliginosus and E. mundus showed negligible control of Bemisia tabaci on short-cycle autumn crops.
• Encarsia formosa was the most effective beneficial insect, but overall Trialeurodes vaporariorum population growth was not significantly affected.
• M. caliginosus and E. mundus establishment was poor, likely due to insecticide residues, low prey availability, and de-leafing practices.
• Indigenous natural enemies were present but contributed minimally to overall whitefly control.

Conclusions:

• Biocontrol of whiteflies using commercially available beneficial insects proved inadequate in Sardinian tomato greenhouses under the tested conditions.
• Insecticide residues and disruptive cultural practices (e.g., de-leafing) significantly hampered the establishment and effectiveness of natural enemies.
• Re-evaluation of cultural practices is crucial for successful implementation of biological control programs in greenhouse tomato systems.