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