Variations in insect-induced fruit damage and yield of okra Abelmoschus esculentus after insecticide treatments at different phenological growth stages

Several phytophagous insect pests are known to attack okra, Abelmoschus esculentus (L.) Moench in the field. However, information on the fruit-damaging species and the effective time for insecticide application(s) is still scanty. Field experiments were conducted in ۲۰۱۷ and ۲۰۱۸ to identify the categories of damage inflicted on okra fruits by associated insect herbivores and to ascertain the phenological growth stage in which insecticide applications will significantly reduce insect-induced fruit damage and improve crop yield. Treatments consisted of the application of Cypermethrin ۲۰EC at two-week intervals on NHAe۴۷-۴ variety of okra during the vegetative stage (VGS), reproductive stage (RGS), VGS + RGS, and no spray (control). The setup was in randomized complete blocks with four replicates. Results showed that incisions, feeding lesions, localized discolorations, bumps, distortions, and larval exit holes are the major fruit damage symptoms caused by field insect pests of okra. Generally, fruit damage was significantly reduced, while fruit yield was higher in plots that received insecticide sprays at vegetative and reproductive stages than in the control. Fruit production increased significantly by ۵۶.۹–۶۹.۶% and ۵۷.۷–۷۳.۱% in ۲۰۱۷ and ۲۰۱۸ in treated plots compared to control, respectively. Fruit damage was reduced by ۳۷.۵-۹۲.۵% (۲۰۱۷) and ۴۴.۶–۹۴.۶% (۲۰۱۸), and fresh fruit yield of okra was increased by [۵۸.۸–۷۵.۰% (۲۰۱۷) and ۶۳.۱-۷۶.۱% (۲۰۱۸)]. We conclude that an effective field management strategy for insects associated with okra fruit damage should include potent control tactics at the crop's vegetative and reproductive growth stages.

کلیدواژه ها:

Crop phenology ، cypermethrin ، fruit damage ، okra ، pest control