Risk assessment of Episimus unguiculus (Lepidoptera: Tortricidae), a biological control agent of Schinus terebinthifolia (Sapindales: Anacardiaceae) in Hawaii, USA

ABSTRACT

Schinus terebinthifolia Raddi (Anacardiaceae) is an introduced ornamental tree from South America that has become one of the most invasive weeds in Hawaii and Florida, USA. Exploratory surveys in the plant’s native range from 1950 to 2014 identified several potential biological control agents. One of these is the leaflet rolling moth Episimus unguiculus Clarke (Lepidoptera: Tortricidae), previously known as Episimus utilis Zimmerman. This biological control agent was released in Hawaii in the 1950s where high densities were occasionally observed, leading to partial control of S. terebinthifolia by the 1960s. Larvae are leaf tiers capable of completely defoliating small plants. In order to investigate the release of E. unguiculus in the continental USA, a series of laboratory no- choice, and multiple-choice tests were conducted in Florida, and a preliminary open field test with a native plant in Hawaii. Under the confined laboratory conditions imposed during the no-choice tests, E. unguiculus accepted the economically important Pistacia spp. and several other non-target plants for oviposition and development. However, in the multiple-choice tests E. unguiculus exhibited a clear preference for S. terebinthifolia relative to non-target plants accepted in the no-choice tests. Overall, the results of field observations during surveys in South America and Hawaii and host range studies completed in Hawaii and Florida showed that E. unguiculus is a narrow specialist on S. terebinthifolia, its natural host plant.

KEYWORDS:

• Brazilian peppertree
• Christmas berry
• invasive weed
• risk analysis

Acknowledgements

We thank the following former University of Florida graduate and undergraduate students for their technical assistance: Abhishek Mukherjee, Roberto Granja, Onour Moeri, Kristine Nichols, Danielle Salazar, Mona St. Val, and Tanya Stevens. We are indebted to Mr. Ken Teramoto, former Bio-Control Section Chief, Hawaii Department of Agriculture, for providing historical data from the Hawaiian host range tests. Finally, we thank Andrew Sanders for providing the S. polygama plants, the ML Macadamia Nut Co., Pahala, HI for installing the irrigation system for the R. sandwicensis field test, and the students/staff of the Federal University of Parana, Curitiba, Brazil for their contributions.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

J. P. Cuda http://orcid.org/0000-0002-4744-5416

Additional information

Funding

This work was supported by grants from the Florida Fish and Wildlife Conservation Commission (formerly Florida Department of Environmental Protection) under Grant SL849: the Florida Exotic Pest Plant Council, and the South Florida Water Management District under Grant UPN00012002.