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VOL. 11, ISSUE 3 (2026)
Threshold responses of Okra (Abelmoschus esculentus l. moench) to increasing densities of adult Nisotra dilecta Dalman (coleoptera: chrysomelidae): implications for crop damage and yield loss
Authors
Edache Ernest Ekoja
Abstract
Adult flea beetles (Nisotra dilecta
Dalman) are important defoliators of okra, yet quantitative information on crop
responses to increasing infestation densities is limited. This study evaluated
the threshold responses of okra to increasing densities of adult N. dilecta
under screen-house and field conditions at Joseph Sarwuan Tarka University,
Makurdi, Nigeria. Six infestation densities (0, 5, 10, 20, 30 and 40 adult
pairs per cage) were assessed in completely randomized and randomized complete
block designs for the screen-house and field experiments, respectively.
Increasing beetle density significantly (P< 0.001) increased foliar injury
while progressively reducing vegetative growth, delaying flowering and
depressing yield. Relative to the uninfested control, shoot height declined by
5.2–67.2% in the early season and 4.7–54.4% in the late season, whereas shoot
biomass decreased by up to 71.0 and 71.8%, respectively. Fresh fruit yield
declined by 11.0–67.6% in the early season and 12.2–70.6% in the late season.
Beetle density showed strong positive correlations with leaf damage (r
=0.901–0.938; P< 0.001) and strong negative correlations with growth and
yield attributes (|r| =0.718–0.927; P< 0.001). Second-order polynomial
models (R² =0.85–0.91) identified a distinct threshold response, with
rapid deterioration in crop performance beyond approximately 10–20 adult pairs
per cage. These findings indicate that okra can tolerate low N. dilecta
infestations; however, beetle densities exceeding approximately 20-pairs (8
adults per plant) result in marked physiological stress and economically
important yield losses, providing a quantitative basis for establishing
economic thresholds and developing evidence-based integrated pest management
strategies.
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Pages:64-71
How to cite this article:
Edache Ernest Ekoja "Threshold responses of Okra (<i>Abelmoschus esculentus</i> l. moench) to increasing densities of adult <i>Nisotra dilecta</i> Dalman (coleoptera: chrysomelidae): implications for crop damage and yield loss". International Journal of Entomology Research, Vol 11, Issue 3, 2026, Pages 64-71
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