Browsing by Author "Anikwe, J.C."

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    Evaluation of Field Damage and Chemical Control of Outbreak of Sahlbergella singularis Haglund in a Cocoa Plantation in Ibadan, Nigeria
    (2009) Okelana, F.A.; Anikwe, J.C.
    Field evaluation of damage caused by the brown cocoa mirid, Sahlbergella singularis was based on three parameters, namely, lesions on pods, cankers on trunks and dieback of twigs. Damage assessment based on scoring exceeded 75% for damage to the trunks and fan branches while damage to the pods was more than 50% by the second cocoa season. Laboratory evaluation of endosulphan 35 EC applied at 0.25% active ingredient compared favourably well with the standard miricide as all mirid populations were knocked down 40 minutes after exposure to filter paper impregnated with endosulphan. The endosulphan was found to be faster acting than the standard at 0.25. Control of mirids in the field was similar to results obtained in the laboratory. There was only 12% recovery 28 days after spray application with endosulphan in the field while the standard miricide gave a similar result of 15% recovery on the 28th day. No mirid mortality was recorded in the control plots. The control of mirids with endosulphan was very efficacious but cocoa beans treated with endosulphan must be analyzed to determine its residue content before final approval or rejection of the insecticide for use on cocoa.
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    Evaluation of resistance in selected cocoa genotypes to the brown cocoa mirid, Sahlbergella singularis Haglund in Nigeria
    (2009) Eskes, A.B.; Aikpokpodion, P.O.; Okelana, F.A.; Omoloye, A.A.; Anikwe, J.C.
    The use of host-plant resistance is the most economic and ecologically sound option for the control of the most important insect pest of cocoa, Sahlbergella singularis leaving no deleterious side effects on the produce and the environment. 44 genotypes comprising 24 hybrids and 20 clones were assessed for antixenosis whereas 25 and 28 genotypes were tested for antibiosis and tolerance, respectively. The brown cocoa mirids showed significant non-preference for genotypes T65/7xT57/22, T65/7xT9/15, P7xPa150, T53/5xN38, T53/5xT12/11, T65/35xT30/13, F3 Amazon, T86/2xT16/17, T65/7xT53/8, T86/ 2xT65/35, T82/27xT16/17, T9/15, T12/5, T30/13, C77, T53/8, T53/5, EET59, Pa150, UF 676, Amaz15-15, BE 10, SPEC54 and Pa107. Mirid survival (antibiosis) was lowest in EET59 (28.7%) while it ranged from 52.2 to 67.8% in genotypes BE10, Amaz15-15, SPEC54, UF 676, P7xPa150, and Pa107. The indigenous clone N38 had the highest number of lesions of 12.2 in the field while EET59, IFC-5, Playa Alta, BE10, Amaz15-15 and SPEC54 had mirid lesions of 2.7, 3.3, 5.2, 5.3, 5.5 and 5.5; respectively. However, in terms of recovery from mirid damage and dieback progression which were important parameters assessed in tolerance, Clones ICS1, EET59, BE 10, Amaz15-15, SPEC54 and Pa 102 showed highest rate of recovery from mirid damage and lowest dieback progression. Clones UF 676, C77, Pa150 and F3 Amazon also showed moderate recovery from mirid damage with mean scores of 1.2, 2.3, 1.6, 1.4, 1.7, 1.4 and 1.5, respectively. UF 676, C77, Pa150 and F3 Amazon performed moderately well in terms of tolerance. Some of these genotypes such as BE10, Amaz15-15, SPEC54, UF 676, P7xPa150, and Pa107 were very consistent in all mechanisms of resistance tested and therefore adjudged as resistant cocoa genotypes.
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    Evaluation of the toxicity of Actara 25 WG for the control of the cocoa mirid Sahlbergella singularis Hagl. (Hemiptera: Miridae) in Nigeria
    (2009) Anikwe, J.C.; Okelana, F.A.; Asogwa, E.U.; Ndubuaku, T.C.N.
    In Nigeria, the brown cocoa mirid Sahlbergella singularis is responsible for over 30% yield loss in cocoa. Insecticides still remain a very important component among the strategies for effective control of major insect pests of cocoa in Nigeria. The Cocoa Research Institute of Nigeria (CRIN) has the “National Mandate” to evaluate and recommend new insecticides for use on cocoa in Nigeria. The mortality rates of mirids on exposure to the various concentrations (0.01, 0.013, 0.015 and 0.02%) of Actara 25 WG increased with period of exposure of the mirids in the laboratory. Both Actara and the Standard Miricide were similar at 0.020% concentration as both gave a 100% kill of mirids at the 90th min. No mortalities were recorded in control cages throughout the exposure period. The insecticide did not produce any adverse side effects on cocoa seedlings and mature plants sprayed with the various concentrations over the years. The relative toxicity of the insecticide at the four different concentrations to adult mirids, 24 h after the first field treatment application, was 93.3, 82.4, 81.8 and 100% adult mortality, respectively. In the case of the nymphal mirids, percentage mortality was 89.6, 81.5, 86.8 and 94.3% for the various concentrations, respectively. The population of both the adult and nymphal mirids crashed to almost zero (0) in most cases suggesting about 100% mortality 24 h after the second spraying on the residual mirid populations. Mirid numbers remained so low until the third spray application after which it was unnecessary to spray the sub-plots, thereafter. Spraying of mature and fruiting cocoa farms at application rate of 0.015% was found adequate and recommended taking into consideration the impact of the product on the environment and for economic reasons.