Host preference and potential climatic range of Cyanotricha necyria (Lepidoptera:Dioptidae), a potential biological control agent of the weed Passiflora mollissima in Hawaiian forests

Abstract

Passiflora mollissima is a cultivated vine, native to the higher Andes Mountains of northern South America. Introduced to Hawaii, probably as an ornamental, the plant has escaped and become well established in mountain rainforests. Here, its uncontrolled growth--presumably due to the lack of any natural enemies--rapid rate of spread and impact on the native forest trees and shrubs have led to its being declared the most serious introduced weed in this unique ecosystem. In an effort to establish biological control of this weed, a South American moth, Cyanotricha necyria, has been selected as a promising candidate for eventual release in Hawaii. A colony of this insect was established in an insect quarantine facility at Hawaii Volcanoes National Park and used to conduct oviposition, host preference, and climatic range studies. The studies indicate that C. necyria, if released in Hawaii, poses no threat to any native or agricultural plant, with the exception of a few other species of the genus Passiflora, all of which are introduced, and most of which are weeds. While a few larvae under laboratory conditions occasionally completed development on passionfruit, P. edulis, we feel G. necyria is not a threat to this small industry (9100 acres in 1984) based on (1) its expected climatic range 750m and above, (2) unsuitability of P. edulis foliage as a food source for larval development, and (3) nonacceptability of P. edulis foliage as an oviposition site by females. Cyanotricha necyria, if released, may pose a slight risk to the noncommercial P. ligularis in certain areas of the higher forests of Hawaii, and a very small, but acceptable risk to the other species of Hawaiian Passiflora.