Abstract:
Earias species are serious pests of cotton and other malvaceous
plants in the tropics. The biology of &. Snsu1q-m and g, biplam
specifically as pests of okro in Nigeria, was investigated in the
field and the laboratory from September 1984 - July 1985 at the
University of Nigeria, Nsukka,
From the laboratory studies, f ecwndity , incubation p e r i d ,
pre-oviposition period, mean durations of larval and pupal stages,
adu1t"longevity as w e l l as the duration of l i f e cycles of the moths
were established,
Based on frequency distribution of head capsule widths of
field-collected and laboratory-reared larvae, and direct count of
shed head capsules of these internal feeding larvae, 5 imaginal
stages were confirmed for the species. Okro proved to be a suitable
alternativg host plant for these mothsytheir l i f e cycles at
near natural atmospheric conditions in the laboratory being
+ + 21-75 - 1.37 days and 26.18 - 2.09 days for g. insulana and
E, biplaqa respectively, Besides, larvae fed solely - on okro
fruits (seeds) produced viable progeny. Fecundity of these moths
+ (whose larvae were raised on okro seeds) was very low (8 - 3.77
+ and 9.3 - 3.51 eggs for insulana and g, biplaqa respect~vely).
x i i
In nature -E, .in sulana was most cmmon during the dry season while
-Eo biplaqa occurred mostly during the rainy season,
Pest ihcidence in the f i e i d , evidenced by larval puncturing
of a d entry into okro f r u i t l e t s , commenced a t fruiting and lasted
virtually till death of the host plants. Overall damage to
unabortecl okro f r u i t s was 23.06% while abortion of f r u i t l e t s
resulting from larval attacks amounted t o 10.83%, Consequently
it is concluded that these two moth species are normally no serious
pests of okro as they are of cotton. The heaviest larval damage of
okro f r u i t s during this study occurred about the month of January
which coincided with the dry season, while the l e a s t damage occurred
about May during the rainy season. The l a t t e r situation fortdtously
f i t s i n t o t h e cultural practices of okro farmers of Southern Nigeria,
x i i i
