Field biology of Pyrausta perelegans (Lepidoptera: Crambidae): a flower bud-feeder on Passiflora mollissima, an invasive vine in Hawaiian forests.

M. M. Ramadan, G. P. Markin, M. W. Johnson

Abstract


This study is a continuation of efforts to monitor a population of the biological control agent, Pyrausta perelegans Hampson (Lepidoptera: Crambidae), which specializes on the flower buds of the forest invasive vine Passiflora mollissima (H.B.K.) Bailey. Post-establishment studies were conducted to evaluate the effect of P. perelegans and factors affecting its colonization potential shortly after its establishment in the Olaa rain forest, Hawaii Volcanoes National Park (1800 m elevation), island of Hawaii. Moth population growth was monitored over a period of 16 months using a UV light trap. The moth appeared during months of 1992-1993, with a maximum population build-up during May (0.67 moth/night) and October (0.6 moth/night) of 1992. In March and May of 1993 the moth population peaked at an average of 0.4 moth/night. Mean moth catch per night during the two years was not significantly different. Overall mean percentage of vines infested with eggs of P. perelegans was 5.5% with a mean of 4.7 eggs per vine. Most of the eggs (75%) were deposited on the underside of young leaves with midrib lengths ranging from 2.5 to 6.5 cm. The overall percentage of egg parasitism by Trichogramma chilonis Ishii was 9.2%. Mean larval infestations were 7.5%, 2.0%, and 0.4% in small to medium buds (<1 - 6 cm), large buds (7 - 11 cm), and opened flowers (11 ->15 cm), respectively. Infestation was significantly higher in small to medium buds than large buds or opened flowers. No larval parasitism was observed in Olaa rain forest during this study. However, parasitoids recovered from other local Lepidoptera developed successfully in P. perelegans larvae in the laboratory. Laboratory and field observations on feeding behavior and establishment status in other areas on the Hawaiian islands are also reported.

Keywords


Passiflora mollissima; Pyrausta perelegans; classical biological control; forest weed; insect colonization; Hawaii

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