UC Delivers

Teamwork Controls Major Pest in Avocado

The Issue

Teamwork Controls Major Pest in Avocado
Scirtothrips perseae.
The avocado industry contributes $350 million dollars in annual revenue to the California economy. The survival of the avocado industry was seriously threatened when a new insect pest species of thrips (Scirtothrips perseae) was discovered in Ventura and Orange counties in June 1996. The species was previously unknown to science, therefore no information was available to assist in the research effort.

What Has ANR Done?

Farm advisors Ben Faber and Phil Phillips began detection surveys in the fall of 1996. These surveys determined the movement and extent of the infestation. They requested the assistance of UC Riverside entomologist Mark Hoddle to investigate the potential for biological control and Joseph Morse to help with chemical control trials. The USDA helped determine the species of this new pest in 1997.
 
Capitalizing on their individual expertise, the team of four researched the field biology, economic threshold, and local natural enemies of the pest. Research by Morse, Philips, and Faber demonstrated that three selective pesticides -- abamectin, spinosad and sabadilla -- could be used to manage avocado thrips without leading to secondary pest upsets.
 
Over a three-year period, Faber and Phillips determined when and why fruit damage was occurring, how many thrips caused economic damage, and much of the selective treatment parameter information. Hoddle determined that high temperatures shifted the sex ratio of this insect, explaining why its populations crashed during the summer. Meanwhile, biocontrol agent release trials demonstrated that none of the known biocontrol agents were effective at controlling this new pest and that the natural enemies being sold to growers were not effective.
 
Hoddle and Phillips traveled the native home of the avocado (Mexico, Central America and the Caribbean) and determined that the pest originated in southern Mexico, that there were no other significant natural enemies of this pest, and that Scirtothrips perseae was not considered a significant pest in its native home. Unlike in Mexico, cool spring weather in California delays leaf flush and encourages large populations of this insect on the newly developing fruit.

The Payoff

$25 million saved a year

The impact of the research was immediate and significant. Each year since the completion of this study, the avocado industry has saved millions of dollars in losses and this pioneering research added significantly to the scientific literature on thrips and avocado pest management. Hoddle, Morse, Faber and Phillips maintained a strong linkage with the avocado industry through grower field trials, grower meetings, field days, industry publications and an annual industry research conference. This enormously successful project would not have been possible without their collaborative efforts as a UC research and extension team.

Contact

Mark Hoddle, CE Bio Control Specialist, UC Riverside, mark.hoddle@ucr.edu
Ben Faber, farm advisor, UC Cooperative Extension Ventura County, bafaber@ucdavis.edu
Phil Phillips, UCIPM Area IPM Advisor, UC Cooperative Extension Ventura County, paphillips@ucdavis.edu
Joseph Morse, Professor of Entomology, UC Riverside, joseph.morse@ucr.edu