Effect of neem seed kernel extract on major insect pests of Cowpea (Vigna Unguiculata (L.) Walp and influence on yield under calendar and monitored sprays

By EBENEZER OGHENEWORO EGHO and STEPHEN OGAGAOGHENE EMOSAIRUE


Abstract

The present study tested 5% aqueous extract of the seeds of Dogoyaro tree, Azadirachta indica, neem seed kernel extract (NSKE) for insecticidal property in the control of four major insect pests of cowpea - the cowpea aphid, Aphis craccivora Koch, legume bud thrips Megalurothrips sjostedti Tryb, legume pod borer, Maruca vitrata Fab. and pod sucking bugs. The experiments involved calendar spray at 7 days' intervals (CA.S7) carried out 5 times, calendar spray at 10 days' interval (CA.S10) carried out 4 times and monitored spray (MOS)involving monitoring of  insect pest infestation/damage before chemical application.  The results showed that CA.S7 significantly reduced (P<0.05) M. sjostedti damage when compared to control in the early season.  All the treatments slightly controlled flower bud thrips. Similarly, M. vitrata population was slightly reduced at CA.S10 and MOS.  In the late season, CA.S7 slightly suppressed M. sjostedti.  Population of flower bud thrips were significantly (P<0.05) controlled by the NSKE treatments.  CA.S7 and CA.S10 slightly controlled M. vitrata.  Grain yields in the early season were highest in CA.S7 (405.10kg ha-1), followed by MOS (405.10kg ha-1) and CA.S10 (367.40kg ha-1) had the least. In the late season, grain yields were highest in CA.10 (549.80kgha-1); this was followed by CA.S7 (398.90kgha-1) and MOS, (297.90kgha-1) of the neem seed extract treatments. Control had the least yield (266.40kgha-1).  Generally, there was no significant difference in grain yield among the NSK treatments.  The study provides (1) evidence that insect pest control in calendar spray at 10 days’ intervals and monitored sprays are as beneficial as calendar spray at 7 days’ intervals, since this would reduce the number and cost of chemical application (2) that NSKE can form component of the integrated pest management in cowpea cultivation.

 

Key Words : Cowpea, insect pests, early/late seasons, Asaba, southern Nigeria.

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