Poultry manure application and varietal effects of chilli-pepper (Capsicum species) on insect pests and disease in a humid-tropical environment
Cultural practices such as organic manure application can affect soil fertility and also insect pest and disease incidence on the plant. The effect of poultry manure application was therefore evaluated in relation to the infestation by major insect pests and disease of pepper in a humid tropical agro-ecosystem. Treatments comprised three varieties of chilli pepper, Capsicum annum vars. tartashi and tarugu and Capsicum frutescens var. Birds eye chilli, and three Poultry Manure (PM) rates: 0, 20, and 40 t ha-1, in all possible combinations. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. Poultry manure (PM) used was found to be high in nitrogen (2%) but very low in available phosphorus (0.05 ppm) and potassium (0.24 meq/100g soil) as evidenced from the chemical analysis. Aphids (Myzus persicae Sulzer and Aphis gossypii Glov.), mirids (Helopeltis schoutedeni Reuter), flea beetles (Nisotra=Podagrica sjostedti Jacoby and Podagrica uniforma Jacoby), variegated grasshoppers (Zonocerus variegatus L.), white flies (Bemisia tabaci Genn.) and striped blister beetles (Epicauta albovittata Gestro) were the insect pests sampled from the plants in the field. Symptoms of Pepper Veinal Mottle Virus (PVMV) were also evident. All the varieties were susceptible to PVMV with a disease incidence of between 37 and 45%. Counts taken at 100 days after transplanting (DAT) showed that increasing rates of poultry manure significantly (P<0.05) increased aphid, mirid and grasshopper infestations as well as incidences and severities of Pepper Veinal Mottle Virus (PVMV) symptoms compared to where no manure was applied. The different varieties significantly (P<0.05) affected the infestations by insect pests as well as the incidences and severities of PVMV symptoms, such that PVMV symptoms and insect pests were found to be more on "Birds eye chilli”, a local pepper variety, than any other given the same treatment. Poultry manure and variety interactions were significant (P<0.05) on some insect populations, incidences of PVMV symptoms and yield attributes. Counts of Bemisia tabaci at 100 DAT and number of aborted fruits, on the other hand, did not differ significantly amongst the manure levels, varieties and their interactions. However, there was a progressive trend of increasing Bemisia infestation with increasing manure rate. Poultry manure at 20 t ha-1 produced the highest fruit weight. These results are discussed in light of soil fertility on the susceptibility of chilli pepper to insect pests and disease in this agro- ecology.
Keywords: Poultry manure, Insect pests, Pepper veinal mottle virus.
Agro-Science Vol. 5 (2) 2006: pp. 49-58