Refining trapping protocols for field management of Podagrica spp

Abstract

Podagrica uniforma Jacoby and P. sjostedti Jac. are two of the most economically important flea beetles associated with okra plants in Africa. Field experiments were conducted in different okra fields (2018–2019) to examine the beetles’ response to colours [black, blue, brown, green, orange, pink, purple, red, white, yellow, and clear (control)] using traps coated with Temmen-Insektenleim adhesive. We also determined the effect of trap size, installation height, position in the field, and time of day on the number of Podagrica spp. captured. Both species of Podagrica exhibited distinct preferences for trap hue and value. Canary yellow [R (253 ± 2), G (249 ± 4) and B (157 ± 2)] attracted more beetles to traps than other colours. A higher number of Podagrica spp. was captured when traps were: placed within an okra field; 22 × 30 cm in size; and installed at 80 cm height relative to other trap attributes. More beetles were trapped between late afternoons to nightfall (14:00–18.00 h) than catches from other periods of the day. Additionally, canary yellow sticky trap reduced over 70% of adult Podagrica spp. infesting early-and late-plant okra relative to the control. Fresh fruit yields of okra from plots with the trap and those treated with cypermethrin (standard check) were not significantly different from each other. We conclude that colour plays an important role in the behavioural responses of Podagrica spp.; the use of canary yellow along with the best trap characteristics identified in this study was effective against the beetles and a safer alternative to synthetic insecticide.