Influence of different nutrient applications on insect populations and damage to cabbage

2011

English

Objective: Amendments aiming to improve soil fertility have been found to increase pest populations on plants. This study was conducted to evaluate the effects of organic (poultry manure) and synthetic (NPK) fertilizers on insect populations associated with cabbage. Methodology and results: Two field experiments were conducted at the Theoretical and Applied Biology Department Garden of Kwame Nkrumah University of Science and Technology and CSIR-Crops Research Institute, Kumasi, Ghana from October 2008 to January 2009 and May to August 2009, respectively. Three main treatments, i.e. NPK 15:15:15 fertilizer at 10g/cabbage plant; poultry manure at 50g/cabbage plant and control (no nutrients) were applied. The experimental set up was a Randomized Complete Block design (RCBD) with three replications. Parameters studied included insect pests’ numbers and their natural enemies. The percentage leaf damage, fruit damage, plant with multiple head damage and yield were determined. Major insect pest recorded included Brevicoryne brassicae, Plutella xylostella, Hellula undalis and Pieris rapae which caused damage to the cabbage plant (Brassica oleracae var. oxyllus). The natural enemies of pests of cabbage identified were the ladybird beetle, (Cheilomenes sp), huntsman spider, Heteropoda venotoria and black carpenter ant Camponotus pennsylvanicus. The control plots recorded cabbage plants with the highest yield in terms of head weight. Both poultry manure and inorganic fertilizers (NPK) generally increased insect pest attack on cabbage plants compared to the control. Conclusions and main findings: It is concluded that when soil amendments such as poultry manure and inorganic fertilizers are applied to restore or increase fertility, pest control measures such as the use of chemical insecticides and other pest management options should be put in place to mitigate the effects of infestation of insect pests on crop productivity.

Mochiah, M. B.; Baidoo, P. K.; Owusu-Akyaw, M.