An agro-economic appraisal of the response of okra to leaf defoliation: Growth and marketable yeild

Abstract

The leaves, shoots, immature pods and dry seeds of okra are used extensively in vegetable food preparations in the tropics. The fruit is rich in minerals and vitamins, which are essential for body functions. The soft and succulent nature of the leaves make them vulnerable to attack and subsequent damage by a range of leaf eating insects, animal pests and man. Such damage results in remarkable yield loss and reduced market value. Identification of the critical stages of attack and extent of loss taking place at each stage of development of the plant could aid in planning strategies for prevention and/or control. Thus, two field experiments were conducted to determine the effect of leaf removal on the growth and marketable yield of okra. The treatments on leaf defoliation at different stages of development consisted of removal of leaves at 4 weeks after sowing (WAS) as early vegetative stage, 6WAS (at floral budding stage) and 8 WAS (at early fruiting stage). The treatments on the degrees of defoliation included the control (no leaf removal), removal of a quarter (D25), half (D50), three quarter (D75) or total removal (D100) of every fully expanded leaf. Different proportions of every leaf were removed with sharpened scissors. Each treatment was replicated four times. The experiment was 3 x 5 factorial with randomized complete block design. Current market price was used to value the yields. The removal of up to a quarter of each leaf did not affect the fruit yield significantly but the yield was significantly reduced by 39, 79 and 86% when ½, ¾ of each leaf and
complete leaf were defoliated, respectively. In money terms, the losses were N26,390($175.93), N52,780($351.87), and N57,876($385.84) per hectare, respectively for these various defoliation levels. Removal of okra leaves during the early fruiting stage led to 82% marketable yield reduction. Complete leaf defoliation was detrimental to fruit yield. The results suggested that okra could tolerate 25% defoliation as might occur from leaf eating insects, human predators or foliage pathogenic infections but beyond this level, it would be detrimental. A programme of control of leaf predators in okra management should therefore commence prior to or
at the early fruiting phase in order to realize yields of good value. Further research on commercial uses of okra and the economics of pest control on okra fields is recommended.

Key words: Agro-economic, Defoliation, Fruiting, Yield, Commercial