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In Hawai‘i, we rely on our forests for fresh water…..

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Presentation on theme: "In Hawai‘i, we rely on our forests for fresh water….."— Presentation transcript:

1 In Hawai‘i, we rely on our forests for fresh water…..

2 Hahai nō ka ua i ka ulu lā‘au. Rains always follow the forest. – ‘Ōlelo noe‘au Ancient Hawaiian proverb

3 Guava takes over native forest Photo courtesy of Carnegie Airborne Observatory

4 Compared with native ‘ōhi‘a forests, strawberry guava-infested forests lose 27% more water, with the difference rising to 53% during dry periods.

5 Strawberry guava also invades non-native forest areas, like this Eucalyptus in Honoka‘a


7 Slide courtesy of Carnegie Airborne Observatory Not all green is good: Native forest cover appears intact in normal aerial views (upper images) of Ola‘a and Wao Kele O Puna forests, but using high resolution hyperspectral imaging (lower images), extensive invasion by strawberry guava becomes visible in pink.

8 Slide courtesy of Carnegie Airborne Observatory

9 Manual Control of strawberry guava is expensive, difficult, -- and it’s not enough. Manual control can be affordable in patches of accessible, lightly invaded forest ($255/acre initially plus $123/acre annual maintenance) But costs rise to $10,000 - $30,000 per acre in densely infested forest Hundreds of thousands of acres are affected across the state - much would require access by helicopter Estimated cost for manual control on east Hawai`i Island conservation lands: over $360 million Requested funds to manually control Miconia in Hawai‘i result in less than $2 million/year statewide Photos courtesy of J. Penniman

10 Costs of Strawberry Guava to Agriculture At least 80,000 acres of agricultural land affected Strawberry guava is a primary source of pest fruit flies Fruit flies impact papaya and dozens of other soft fruits For papaya alone, fruit flies cost farmers $7.8 million/yr* Opportunity costs estimated at $78 million/yr* *McGregor, A.M. 2004 USDA - ARS

11 Target plants for biocontrol in Hawaiian forests US Forest Service Learningto just say no not right now maybe later when resources allow Clidemia Miconia Christmas berry Cape ivy Himalayan raspberry Banana poka Tibouchina Fayatree Strawberry guava National Park Service USGS Univ. of Hawaii Hawaii Dept. Agric. Hawaii Dept. Land & Natural Resources US Fish & Wildlife Service Invasive Species Committees Watershed Partnerships The Nature Conservancy The worst of the worst

12 NOT biological control! - Introduced 1883, before modern protocols - No science, no review, no regulation Modern biocontrol uses only highly specific agents All introductions since 1970s avoided non-targets What about the Mongoose?

13 Proposal: Use the natural enemy of strawberry guava for sustainable, long term management In its native country, strawberry guava lives in balance with other plants because it has natural predators that help keep it from overpopulating The Brazilian scale insect (Tectococcus) is strawberry guava’s natural predator. It feeds on new leaf tissue, causing galls to form. This reduces plant vigor and fruit production (but doesn’t kill the plant or completely stop fruiting) Slowing strawberry guava growth would allow native forest species a chance to compete Effect of Tectococcus: galls on leaves

14 Common guava Tectococcus has never affected common guava or any other agricultural plants in Brazil. Strawberry guava Brazil

15 Quarantine Testing of Tectococcus ovatus In Brazil and in more than 10 years of testing (more than 100 species of native & non-native plants), it has not switched hosts. It needs strawberry guava to be able to survive.

16 Psidium speciesMyrtle Family (non- Psidium ) Other Families strawberry guava (Psidium cattleianum + P. spathulatum) nioi ( Eugenia reinwardtiana ) Surinam cherry (pitanga) cigar flower pukamole Psidium guineense jaboticabaakia Psidium friedrichsthalianum Java plumkoa Psidium guajava rose applemamane common guava varieties:mountain applea'ali'i Puerto Rico #2allspicelongan Waiakea ohia lehua ( Metrosideros polymorpha ) rambutan Allahabad Safeda ohia lehua ( Metrosideros macropus ) naio Fan Retief lehua papa ( Metrosideros rugosa ) pilo Ka hua kula lehua ahihi ( Metrosideros tremuloides ) hapu'u pulu Beaumont Eucalyptus citridora plus 50 other species Thai maroon Eucalyptus globulus paperbark plus 19 other species Species Tested: Tectococcus could not live on anything but strawberry guava

17 Impact of Tectococcus

18 Expected Impacts from Tectococcus Gradual increase of insect population at release sites Reduced strawberry guava growth and fruiting after 2-3 years at release sites Slow spread of Tectococcus from release sites due to limited mobility Reduced growth rate and spread of strawberry guava on each island would be visible over a period of decades Increased effectiveness of other control methods (by reducing resprouts and spread of seeds)

19 Protection for backyard trees Limited mobility of Tectococcus lowers likelihood of spread to trees in yards Tectococcus can be controlled by application of oil sprays (petroleum-based and organic plant oils available)

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