Influence of Plant Spacing on Insect Population, Growth and Yield of Okra in Sierra Leone

Abstract

Okra is a very important vegetable in the field of nutrition and health care in Sierra Leone. The major limiting factors in okra production are incidence of insect pests and improper plant spacing. The present field research was undertaken at the Department of Crop Protection, School of Agriculture, Njala University to evaluate the effect of plant spacing on insect pest population, growth and yield, and profitability of okra production in Sierra Leone from 2017 to 2018 main cropping seasons. Five levels of plant spacing 50 cm × 40 cm (50,000 plants per hectare), 60 cm × 30 cm (55,556 plants per hectare), 60 cm × 40 cm (41,667 plants per hectare), 70 cm × 30 cm (47,619 plants per hectare), and 70 cm × 40 cm (35,714 plants per hectare) were adopted as treatments with three replications in randomized complete block design. The results of analysis of variance revealed that plant spacing were significant (P < 0.05) on insect population, plant height, leaf area, damage leaves, yield and yield components of okra at 4 and 8 weeks after planting (WAP) during 2017 and 2018 main cropping seasons. Okra cropped in plant spacing 50 cm x 40 cm (Recommended rate) inclined the highest number of insects, plant height, leaf area, damage leaves and yield at 4 and 8 WAP in both years followed by 60 cm x 40 cm plant spacing, while the reverse also holds true with 70 cm x 40 cm plant spacing. The profitability analysis revealed that the recommended plant spacing of okra (50 cm x 40 cm) produced the highest gross margins of Le 18,333,000.00 plants per hectare (ha-1) and Le 21,363,000 plants per hectare (ha-1) respectively during 2017 and 2018 main cropping seasons of okra production. In conclusion, increasing the plant spacing above the recommended plant spacing (50 cm x 40cm) could reduce insect population and leaf damage on okra, but will significantly decrease okra growth and yield, and profitability. Hence, in order to achieve maximum productivity of okra in the Njala area, the Clemson spineless variety of okra should be planted at a plant spacing of 50 cm x 40 cm. However, integrating plant spacing with other cultural methods of controlling insect pests of okra should be investigated in order to determine a sustainable and cost-effective method of controlling insect pests of okra.