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June 1 - 3 , 1978 - University of Hawaii at Manoa

June 1 - 3 , 1978 - University of Hawaii at Manoa

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BIOLOGICAL CONTROL OF WILDLAND WEED PESTS IN<br />

HAWAI'I--IS IT A FEASIBLE SOLUTION?<br />

John W. Beardsley, Jr.<br />

Department <strong>of</strong> Entomology<br />

<strong>University</strong> <strong>of</strong> <strong>Hawaii</strong> <strong>at</strong> <strong>Manoa</strong><br />

Honolulu, <strong>Hawaii</strong> 96822<br />

The problem <strong>of</strong> aggressive exotic weed species invading<br />

n<strong>at</strong>ive <strong>Hawaii</strong>an ecoysystems and overwhelming or out-competing<br />

endemic plants has been a recurrent one since man's arrival in<br />

these islands. The Polynesians brought with them the hau and the<br />

kukui, among others, which have since become widespread and abundant<br />

elements <strong>of</strong> the <strong>Hawaii</strong>an flora. These <strong>at</strong> least are plants<br />

which <strong>at</strong> the time were useful. Since the arrival <strong>of</strong> the Europeans,<br />

we have seen Hawai'i's forests invaded in successive waves<br />

by lantana (Lantana camara), the guavas (Psidium guajava and<br />

- P. c<strong>at</strong>tleianum), rose myrtle (Rhodomyrtus tomentosa), the firetree<br />

(Myrica<br />

blackberries (Rubus spp. ) , melastoma<br />

(Melastoma mala P <strong>at</strong>hricum), banana pok~ssiflora mollissima),<br />

Koster's curse (Clidemia hirta), and New Zealand tea (Leptos<br />

ermum sco arium), to mention a few <strong>of</strong> the more obnoxious<br />

-. -77<br />

species Severa <strong>of</strong> these are still rapidly extending their<br />

ranges and some, such as banana poka and Koster's curse, appear<br />

to be causing the rapid decline and disappearance <strong>of</strong> elements <strong>of</strong><br />

the endemic flora in those areas which they have invaded. I am<br />

sure th<strong>at</strong> the botanists could name additional species which<br />

invaded wildland ecosystems within the past few decades, and I am<br />

almost certain th<strong>at</strong> we will be seeing other species, which are<br />

not yet considered to be problems, developing into serious pests<br />

in the future.<br />

Biologists concerned with the preserv<strong>at</strong>ion <strong>of</strong> n<strong>at</strong>ive<br />

<strong>Hawaii</strong>an ecosystems and the individual elements there<strong>of</strong>, are<br />

faced with a serious dilemma. The cost <strong>of</strong> physically or chem-<br />

ically removing or killing invading weed species which thre<strong>at</strong>en<br />

n<strong>at</strong>ive ecosystems is generally prohibitive, given the budgetary<br />

limit<strong>at</strong>ions under which most <strong>of</strong> us must oper<strong>at</strong>e, and excepting<br />

incipient infest<strong>at</strong>ions which involve rel<strong>at</strong>ively small and acces-<br />

sible areas. Furthermore, physical and chemical methods <strong>of</strong>ten<br />

have undesirable side effects such as the inadvertent destruction<br />

<strong>of</strong> n<strong>at</strong>ive plants. Also, such methods are rarely 100% effective,<br />

which means th<strong>at</strong> within a few years the tre<strong>at</strong>ed area, in all<br />

probability, will have been reinvaded from adjacent untre<strong>at</strong>ed<br />

1 Published with the approval <strong>of</strong> the Director <strong>of</strong> the <strong>Hawaii</strong> Agri-<br />

cultural Experiment St<strong>at</strong>ion as Journal Series No. 2249.

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