Project WC-DM-10-01
Cynthia King¹, Robert Hauff¹, Leyla Kaufman², and Mark Wright²
¹,
²
A B C
Figure 1. (A) Healthy Myoporum sandwicense , (B) M. sandwicense flowers and
(C) Myoporum thrips adults.
is a dominant tree species native to Hawaii and is both culturally and ecologically important (Fig. 1A,B). Myoporum thrips,
, is a recently established insect pest which infests
in Hawaii (Fig. 1C). The pest was first found attacking
plants on Big Island in December 2008. Feeding by the thrips causes distortion in young leaves and gall-like symptoms
(Fig. 2A,B).
thrips can disperse over long distances via wind, and may be unintentionally transported by people on goods, specifically plant stock. Infestation causes leaf and branch die-back, and can eventually result in tree mortality (Fig. 2C,D).
thrips likely originate from Tasmania, however the first documented infestation, and subsequent species description, occurred in Southern California where the pest was found to be attacking ornamental
plants. The pest has caused extensive mortality in
plants from San Diego to San Fransisco, demonstrating its resilience across a range of habitats. Given the frequency of inter-island transport of goods and people, the precedence of pest range expansions, and the dispersal abilities of thrips, this species is likely to spread to other Hawaiian Islands.
In 2010 the Hawaii State Division of Forestry and Wildlife (DOFAW) was awarded a US Forest Service Special Detection Monitoring
Program Grant to evaluate the impacts of the thrips on
.
DOFAW has partnered with the University of Hawaii at Manoa,
Department of Plant and Environmental Protection Sciences to complete the project.
1) Define the current distribution of the naio thrips infestation on
Hawaii Island
2) Determine impact of naio thrips across a variety of habitat types and elevational gradients
3) Monitor naio thrips density and distribution over time in infested areas, and measure rates of spread
4) Evaluate the potential for management and control of naio thrips
5) Help train field personnel (state/federal/private) to detect naio thrips and identify incipient infestations
are currently being conducted on state, federal and private lands across Hawaii Island. Presence/absence data are collected and mapped based on visual surveys of plant foliage.
have been established at nine sites on Big Island ranging from 2m - 2128m in elevation (Fig. 2).
are assessed from foliage samples collected monthly (5-10 infested shoots from 5-10 randomly selected trees).
is measured by monitoring 10 randomly selected trees at each site.
Infestation levels and dieback levels for selected shoots are assessed monthly using the following scale: 0 = no galls/dieback; 1 = <33% of the tissue is galled/dead; 2 = 33-66% is galled/dead; 3 = >66% is galled/dead.
that are observed during monthly monitoring are collected, preserved and identified to gain an understanding of potential natural enemies which could contribute to thrips control.
such as elevation, level of disturbance, density of naio, and forest composition are also qualitatively documented to determine association with thrips occurrence and density/infestation.
Oweowe
Kaloko
Honokohau
Pelekane and
Koaia Sanctuary
Kaohe Low, High
Puuwaawaa
Low, Mid, High
Figure 2. Documented distribution of Myoporum thrips in Hawaii.
Based on results of our presence/absence surveys Myoporum thrips have dispersed across most of Hawaii Island, on their own as well with the help of humans (via landscaping plantings).
Naio thrips monitoring has been conducted monthly from October
2010 to present. Kaohe High was the only control monitoring site selected, where naio thrips were not present at the start of the project.
Data indicate that infestation levels and branch dieback have increased over the monitoring period at each site where naio thrips are present, with the exception of Pelekane and Koaia Sancturary (Fig. 3 and 4).
Branch dieback results quickly following thrips infestation (Fig. 5), and has led to tree mortality. Mortality cannot yet be estimated, as resprouting of some apparently dead trees has occurred.
4
3
2
1
Koaia Sanctuary
Kaohe High
Kaohe Low
Kaloko
Oweowe
Pelekane
Puuwaawaa High
Puuwaawaa Low
Puuwaawaa Medium
0
No v'1
0
Dec'1
0
Ja n'11
Fe b'
11
M ar'11 Ap r'1
1
M ay'
11
Ju n'11
Jul
'11
Au g"
11
Sep'
11
Oc t'11
No v'11
De c'1
1
Figure 3. Myoporum thrips infestation increases at monitoring sites.
4
3
2
1
Koaia Sanctuary
Kaohe High
Kaohe Low
Kaloko
Oweowe
Pelekane
Puuwaawaa High
Puuwaawaa Low
Puuwaawaa Medium
0
No v'
10
Dec'10 Jan'
11
Feb
'11
M ar
'11
Apr
'11
Ma y'11
Jun'11 Ju l'11
Au g'
11
Sep
'11
Oct'
11
Nov
'11
Dec'
11
Figure 4. Branch dieback increases as a result of thrips infestation.
3
Kaohe Low
2
2
1
1
0
3
Puu M
Dieback
Infestation
Oweowe
Koaia
0
Oct'
10
No v'1
0
Dec'
10
Jan
'11
Feb
'11
Ma r'1
1
Ap r'1
1
M ay'
11
Ju n'1
1
Ju l'1
1
Au g'
11
Se p'
11
Oct'
11
No v'1
1
De c'1
1
Oct
'10
No v'1
0
Dec'
10
Jan'
11
Feb
'11
M ar'
11
Ap r'1
1
M ay'
11
Jun
'11
Ju l'1
1
Au g'1
1
Se p'
11
Oct
'11
No v'1
1
De c'11
Figure 5. Progression of infestation and dieback at four monitoring sites.
Monitoring data show that both infestation rates and branch dieback are increasing at each monitoring site, with the exception of Koaia
Sanctuary and Pelekane. Infestation and dieback are not actually in decline at these sites: our ratings apply to new foliage, and trees at this site are producing little fresh foliage as a result of the stress.
Pelekane was the first natural area naio thrips were documented at and may indicate what impacts will be observed at other sites. It is possible that specific biotic or abiotic factors will mediate the impacts of
thrips on naio, but those trends are yet to be seen.
The following agencies and people have provided invaluable assistance: Anne Marie LaRosa ( US
Forest Service), and the US Forest Service Forest Health Monitoring Program (Project WC-DM-10-
01). Elliott Parsons (DOFAW), Arnold Hara (UH Hilo), Pat Conant (HDOA), James Bethke, John
Kabashima and David Shaw (University of California Cooperative Extension), Oahu Invasive
Species Committee, Army Pohakuloa Training Area, Big Island Invasive Species Committee,
Kohala Watershed Partnership, Three Mountain Alliance, and Kamehameha Schools. Photos:
Forest and Kim Starr, Gevork Arakelian, John Kabashima.