BIOLOGY OF SPIRAMA RETORTA (LEPIDOPTERA: NOCTUIDAE), A NEW PEST OF ACACIA MANGIUM IN PENINSULAR MALAYSIA

Abstract

An outbreak of Spirama retorta (Lepidoptera: Noctuidae), affecting 800 ha of a one-yearold Acacia mangium plantation, occurred in May to October 1992 in Gunung Besaut Forest Reserve, Perak, Peninsular Malaysia. In the laboratory, more than 60% of larvae reared on A. mangium leaves reached adult stage. Development from egg to adult took 42 days through seven instars requiring 27 days. The moth was medium - sized, having red abdomen and an eyespot on its forewing. The female (x = 64.4 mm), bigger than the male, had greyish-orange forewings with prominent eyespots. The male(x = 58.8 mm) had dark brown to almost black forewings with less conspicuous eyespots. The life table parameters recorded from laboratory population were: the net reproductive rate (Ro) of 203.2, the mean generation time (Tc) of 43.3 days, the intrinsic rate of increase (r_m) of 0.1 and the doubling time of 5.6 days. Results from biweekly sampling showed that the infestation, indicated by the number of trees with larvae, varied from 30% at the beginning of the study, rose to more than 60% in the fourth week and dropped to less than 10% at the end of the fourteenth week. Three tachinids, Carcelia sp.,Exorista sp. and Blepharella sp., emerged from field collected larvae. Larval-pupal mortality due to parasitism was 5.6-43.3%. Predators, Sycanus leucomesus (Reduviidae), Cantheconidea furcellata (Pentatomidae), Mallada basalis (Chrysopidae) and Vespa affinis indosinensis (Vespidae) were observed feeding on the larvae.