ABUNDANCE OF INSECTS IN MAIZE FIELDS AND DEVELOPMENTAL BIOLOGY OF FALL ARMYWORM, SPODOPTERA FRUGIPERDA (LEPIDOPTERA: NOCTUIDAE) ON MAIZE VARIETIES

Abstract

Spodoptera frugiperda (Lepidoptera: Noctuidae) is a newly introduced destructive pest of maize in Bangladesh which causes substantial yield loss to different maize cultivars. Experiments were conducted to study the abundance of insects in the maize fields and development of fall armyworm, S. frugiperda on three maize varieties BISCO51, KOHINOOR1820 and M. GOLD. The study was carried out in three different locations of Dinajpur district such as Noshipur, Sadipur and Karnai. Study revealed that maize aphids Rhopalosiphum maidis (Aphididae: Hemiptera) were most abundant in three different locations. Fall armyworm S. frugiperda, maize earworm Helicoverpa zea (Noctuidae: Lepidoptera), maize stem borer C. partellus (Noctuidae: Lepidoptera) and black cutworm Agrotis ipsilon (Noctuidae: Lepidoptera) were also found in the studied fields during March to May. Ladybird beetle Coccinella septempunctata (Coccinellidae: Coleoptera) and lacewing Chrysoperla carnea (Chrysopidae: Neuroptera) were found as natural enemies. Development of S. frugiperda showed no significant differences while fed on three maize cultivars. The highest longevity of adult female was 39.0 days on the cultivar BISCO 51 while shortest 36.5 days on M. GOLD. The daily fecundity showed significant differences among the three maize cultivars. The maximum number (63.78) of eggs was laid on BISCO 51, while minimum (32.9) oviposited on M. GOLD. The sex ratio (proportion of male) was found maximum on BISCO51 (0.56) while minimum in M. GOLD (0.45). The net reproductive rate (Ro = 195.85), intrinsic rate of natural increase (rm =0.185), finite rate of increase (λ= 1.3) were maximum in BISCO51 Population doubling time (T= 29.42) were maximum in KOHINOOR1820 but minimum in M. GOLD. Therefore, maize aphid (1489), fall armyworm (265), maize stem borer (167) maize earworm (156), and black cutworm (66), were observed as major maize pest. Fall armyworm can develop faster in M. GOLD cultivar than KOHINOOR1820 and BISCO51while in terms of reproductive phase and fecundity.