Effect of silicon and potassium on banana weevil injury in East African Highland banana
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Banana is an important food and cash crop in Uganda where it contributes to the welfare of over 75% of smallholder farming households. However, its productivity has been decreasing due to several biotic and abiotic production constraints. Banana weevil (Cosmopolites sordidus) is particularly a major biotic constraint to banana production in the world but more predominant in developing countries. Enhancement of plant nutrition is an environmentally friendly method for minimizing pest effects. For example, several plant nutrition studies, pointing at beneficial effects of silicon and potassium, have been conducted in many crops against different pests. However, few of such studies have been conducted for banana weevil. Therefore, in this study the effects of silicon (Si) and Potassium (K) as plant nutrients against the banana weevil were elucidated. First, a biophysical survey was carried out in two agroecological zones in Uganda and using boundary line analysis, a relationship between Silicon and banana weevil injury was established. This was followed by a screenhouse experiment. Results from the survey indicated a negative relationship between soil silicon concentrations and banana weevil injury. Weevil injury was more responsive to Si in central than in western Uganda. Experimental results indicated significant (P<0.05) main effects for cultivar throughout experimental period, potassium at 30 days after inoculation (DAI) and Silicon at 45 DAI only. A combination of Si (0.75 g/kg soil) and K (0.75 g/kg soil) resulted into the greatest weevil injury reduction of 21.9% compared to 59.0% for silicon alone at 0.5 g/kg Si. This is comparable to weevil injury levels observed in the weevil tolerant cultivar (M9) by 60 DAI. This confirms that Si and K combination has beneficial effects to susceptible banana cultivars against banana weevil injury. Therefore, application of a combination Si and K at appropriate rates to enhance resistance of susceptible cultivars to banana weevil should be included in its IPM options. However, field experimentation is needed for validation and determination of appropriate application rates for agronomic and economic evaluation.