Pacific Southwest Research Station

Research Topics: Biological Control

Biological Control of Strawberry Guava in Hawaii

Hawaii's native forests are undergoing a silent siege. Each year, countless acres of native forest and land are invaded and degraded by nonnative invasive plants. As far as culprit species go, few are more damaging than the strawberry guava (Psidium cattleianum), or waiawi.

Within a short time after establishment, this invasive fruiting tree forms dense, nearly impenetrable thickets that crowd native species, break up natural areas, and disrupt native animal communities. Strawberry guava thickets also provide refuge for two fruit flies [2.1 MB pdf] that cost Hawaiian agriculture millions of dollars each year in lost potential revenue.

Years of mechanical and chemical treatments have been expensive and largely ineffective in stopping strawberry guava's growth and spread. Without an effective and sustainable means of control, the invasive tree may eventually invade and degrade nearly half of the state's total land area.

For the past 15 years, scientists at the U.S. Forest Service's Institute of Pacific Islands Forestry and colleagues in Brazil and Florida have been conducting rigorous research to develop a biological means of stopping strawberry guava's growth and spread. Their work culminated in 2005, when they prepared a proposal to introduce to Hawaii a carefully studied insect, Tectococcus ovatus, that can help to keep the plant's population in check.

Explore this Web site to learn more about strawberry guava and the threat it poses to native forests and how the Institute of Pacific Islands Forestry proposes to manage the invasive tree using biological control.