Evaluation of the effects of different levels of artificial defoliation on the growth and yield of Cowpeas (Vigna unguiculata)

Author

Matimba, Tinayeishe R.

Title

Evaluation of the effects of different levels of artificial defoliation on the growth and yield of Cowpeas (Vigna unguiculata)

Abstract

Cowpea (Vigna unguiculata) is a legume crop that is important for mainly food security in the semi-arid regions, especially in smallholder farmers in Zimbabwe. Its productivity is often affected by pests that feed on the leaves which causes defoliation. Many smallholder farmers cannot effectively control these pests due to the limited access to pesticides. Therefore, understanding how much photosynthetic cover loss on cowpea plants can tolerate without significant yield reduction is essential for informed pest management. This study evaluated the effects of different levels of artificial defoliation on the growth and yield of cowpea variety IT18. The experiment was laid out in a Randomized Complete Block Design (RCBD), with 4 treatments (0%, 25%, 50% and 75% defoliation) replicated four times. Defoliation was done at 4th leaf stage and it was done manually. The growth assessment was done using vine length and it was measured at 3-week intervals over 15 weeks and the yield was determined using the average number of pods per plant and average weight of the cowpea seeds per plant. Results showed that an increase in defoliation can significantly reduce vine length, pod number and yield. The control treatment (0% defoliation) produced the highest mean pod number of 16.9 whilst 75% defoliation produced the lowest pod number of 6.12. Defoliation beyond 25% affected cowpea yield and that defoliation at an early stage affected vegetative growth and reproductive output. The study concludes that cowpea variety IT18 has a moderate tolerance to leaf loss and that maintaining leaf area above 75% is critical for optimizing yield.

Date

June 2025

Publisher

BUSE

Keywords

Cowpea

Artificial defoliation

Pest management

Vegetative growth

Supervisor

N/A