Influence of Nutrient Sources on Growth Performances and Insect PEST Population of Watermelon (Citrullus Lanatus) (Thunb) in South WEST Nigeria.

In spite of the increasing relevance of watermelon, yield across Nigeria is not encouraging due to insect pest attack and rapid reduction in soil fertility. Susceptibility to pest may be a reflection of differences in plant health as mediated by fertility management. The influence of nutrient source on the population dynamic of insect pest infestation on watermelon were assessed in a Randomized Complete Block Design (RCBD) field experiment using NS 295 watermelon cultivar and four nutrient source treatments (poultry manure (6kg/plot), organo-mineral (4kg/plot) and NPK 15-15-15 (1kg/plot) fertilizer and control (no fertilizer/manure), replicated three times to give a total of twelve experimental plots. Data on growth and yield parameters; plant height, numbers of leaves, number of branches, vine girth, numbers of flowers, fruit weight and insect pest population density were collected on five (5) representative plant stand. Data collected were subjected to analysis of variance (ANOVA) and significant treatment means were separated using Duncan Multiple Range Test (DMRT) at 5% probability level. Soil textural and chemical analysis revealed that the soil is sandy loam, strongly acidic and low in soil fertility. Plant response to treatments showed that growth parameters were positively (P<0.05) improved by the nutrient sources while number of flowers and weight of fruits was not significantly affected by the nutrient sources. The result obtained recorded a significantly (P<0.05) high insect population incidence on plants fertilized with NPK compared to other nutrient sources. The prevalent insect pests observed on the field were: Podagrica uniformis, Podagrica sjostedti, Zonocerous variegatus, Epilachna chrysomelina, Copa occidentalis Dacus curcubitae and Apis mellifera. The result have shown that poultry and organomineral could be used as a substitute for NPK 15-15-15 which increase the productivity of the soil in watermelon production and thereby reduce the increased in insect population incidence associated with NPK 15-15-15 fertilizer application.

Keywords: incidence, insect pest, organomineral, nutrient sources, soil fertility, watermelon