Public Comments Being Accepted on Draft EA Posting on Strawberry Guava Impacts and Proposed Biocontrol Insect

Media Release:

The draft EA for the release of a natural predator (Tectococcus ovatus, a Brazilian scale insect) is open for public comment today (June 23) through July 23, 2010.

Strawberry guava is well-known as an ornamental plant that was introduced to Hawaiʻi from Brazil in 1825. Its fruit are a tangy trail-side snack for some, and the wood is free and plentiful. However, strawberry guava is also a fast-growing tree from Brazil that is spreading in forests statewide, forming dense thickets, outcompeting and replacing virtually all other native and non-native plants, and reducing surface and drinking water.

University of Hawaiʻi researcher Thomas Giambelluca compared forests dominated by native ōhia (Metrosideros polymorpha) with strawberry guava-infested forests, and found that the infested forests lose 27% more water, with the difference rising to 53% during dry periods.

For many decades to come forests dominated by strawberry guava will be diverting water that would otherwise recharge aquifers and streams for our drinking water and farms. If nothing is done to protect native forests, the spread of strawberry guava across island watersheds will result in widespread, perpetual reductions of water to our island water supplies.

Dr. Tracy Johnson of the U.S. Forest Service conducted much of the research on this insect. He found that in its native country, strawberry guava lives in balance with other plants because it has natural predators that help keep it from overpopulating. One of these is a Brazilian scale insect, Tectococcus ovatus, which can only live on two types of strawberry guava, only one of which is present in Hawaii. This bug lives most of its life inside strawberry guava leaves, causing leaf galls or bumps, which reduces the vigor of the plant, but does not kill it.

Resource managers across the state agree that strawberry guava is spreading exponentially and cannot be effectively controlled using herbicides or mechanical/manual methods. Because strawberry guava is so widespread, and the increasing magnitude of damage to native forests and watersheds is so severe, agencies and resource managers have turned to biological control as a sustainable, safe way to help reduce the impacts by slowing down the growth rate.

After more than ten years of research and testing by the US Forest Service and other agencies, the Hawaii Department of Agriculture is proposing the release of the Brazilian scale. The draft EA states that the release of this insect would slow the growth rate and spread of strawberry guava, give Hawai‘i’s native plants a chance for survival, protect the ability of the forests to provide water, and provide better protection for agricultural crops from the fruit flies that breed in the overabundance of strawberry guava fruit.

Observations in Brazil and extensive testing of 100 related and unrelated native, commercial, and ornamental plants have shown that this biological control bug can only live on strawberry guava. In the strongest possible wording for risk analyses, Brazilian scale is “extremely unlikely” to attack non-target plants, now and in the future.

Biocontrol is a tool that is essential to sustainably control the spread of strawberry guava and prevent loss of water and native forests for everyone —there are no other options.

To view the draft EA and other information, visit www.strawberryguavabiocontrol.org

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