Physiological Response of Okra to Flea Beetle Herbivory as Measured by Leaf Loss, Chlorophyll Disruption, and Dry Matter Yield

Abstract

Okra, Abelmoschus esculentus (L.) Moench, is attacked by the adult chrysomelid flea beetles, Podagrica spp. Information on physiological disruptions that occur due to flea beetle infestation affecting okra yield loss is incomplete. Screenhouse and field experiments were established to examine the effects of insect populations on leaf abscission, chlorophyll concentration, and biomass partitioning. Okra plants were grown in wire mesh screen cages and artificially infested with flea beetles, P. uniforma Jac., at population densities of 0, 5, 10, 20, 30, and 40 pairs per plant at 3 weeks after sowing (1 pair = 1 male and 1 female). In both experiments, okra plants had increased leaf abscission up to 100% at the 40-pair level in response to P. uniforma-induced injury. There were no significant differences in chlorophyll concentrations of plants at 0-, 5-, and 10-pair levels of infestation, suggesting the use of a compensatory mechanism by plants; at the 20-pair level a significant reduction occurred. Number of leaves per plant, shoots, roots, and dry fruit and total dry matter yield were reduced with infestation above the 20-pair level. More biomass was partitioned into roots at the 5-and 10-pair levels, but insect damage at populations beyond these levels completely suppressed the plant's ability to partition biomass. Dry fruit yields were reduced more than 50% when beetle populations increased beyond 20 pairs in both experiments. There was a correlation between insect density and number of leaves per plant and shoot,

Copper Uptake and Its Effects on Two Riparian Plant Species, the Native Urtica dioica, and the Invasive Fallopia japonica

“…A further explanation might be that the observed loss of leaves in higher copper treatments caused an increase in chlorophyll production in the remaining leaves to keep the photosynthetic activity of the organism stable. This form of compensation has previously been found as a response to herbivory [ 45 , 46 ].…”

Susceptibility of different Malvaceae crops to herbivory induced by adult Podagrica spp.

“…1-2 mm 2 each on leaf lamina is one of the prominent damage symptoms associated with the beetle's presence on a susceptible host plant. This buckshot could lead to disruption of leaf chlorophyll content, induction of leaf loss, opportunistic infection by pathogenic organisms, reduction in plant's fitness, diminution of plant's dry matter yield, and plant death (Vanlommel et al, 1996;Pitan & Ekoja, 2011;Ekoja et al, 2012). On a host like okra, the beetles could establish up to 90% numerical dominance over other insect herbivores at the plant's vegetative growth stage (Odebiyi, 1980).…”

How pestiferous are maize weevil Sitophilus zeamais (Motschulsky, 1855) (Coleoptera: Curculionidae) and rust-red flour beetle Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae) against dried okra Abelmoschus esculentus (L.) Moench (Malvales: Malvaceae) fruit?

“…Some of the insect pests that attack okra include Podagrica species, Bamesia species and aphids, Zonocerus variegatus, okra red mite, cotton strainer, cotton bollworm and cotton shield bug. They attack the crop and cause significant yield reduction (Kumar et al, 2010;Ekoja et al, 2012). During the time of surplus production, rural famers usually process freshly harvested okra fruits into dried form in order to prevent loss to postharvest decay or the option of selling their produce at ridiculously cheap prices.…”