Field evaluation of mineral oils for insect pests management and yield of cowpea (Vigna Unguiculata) (L) walp in Abraka, Southern Nigeria

By E.O. Egho and S.O. Emosairue   

ABSTRACT
Mineral oils have been successfully used as insecticides to control insect pests on several crops such as cotton in many parts of the world.  Such work is yet to be reported in Nigeria.  This study assayed the effectiveness of three mineral oils - premium motor spirit (PMS), dual purpose kerosene (DPK) and automotive gas oil (AGO) at 0.4% concentration in the management of four major insect pests of cowpea, namely the cowpea aphid, Aphis craccivora Koch, legume bud thrips, Megalurothrips sjostedti Tryb, legume pod borer, Maruca vitrata Fab. and pod sucking bugs.  It also assessed influence of pests control on cowpea yield. The field trials were carried out during the early and late seasons on a public land about half kilometre to Campus 2 of Delta State University, Abraka, Southern Nigeria.  The results indicated that all the tested mineral oils effectively controlled M. sjostedti damage in the early season.  Similarly, AGO controlled M. vitrata and pod sucking bugs.  DPK equally controlled coreid bugs. In the late season, A. craccivora and coreid bugs were reduced by all the mineral oils.  In the early season, grain yields were high as follows: 1,342.90 kg ha-1, 963.30kg ha-1, 836.70 kg ha-1 and 917.80kg ha-1 for DPK, PMS, AGO and control respectively. In the late season, yields were 763.30kg ha-1, 634.60kg ha-1, 578.00kg ha-1 and 375.00kg ha-1 for AGO, PMS, DPK and control respectively.  Grain yields were significantly higher (P<0.05) in the early than late season. Delay and reduced flowering were observed in the field.  Elimination of these factors could improve the use of mineral oils in the cultivation of cowpea.  The information given here can be used to strengthen the integrated pest management programme in the control of cowpea insect pests.

Key words:  Cowpea, insect pests, mineral oils, early/late, Abraka, Southern Nigeria.

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