Dynamics of fall armyworm spodoptera frugiperda (smith) (lepidoptera: noctuidae) in Morogoro and prospects for insecticide-based management options

Dissertation

Fall armyworm (FAW) Spodoptera frugiperda is one of the most devastating polyphagous field crop pests in many parts of the world, including Tanzania. This study aimed at determining the influence of altitude on the abundance of S. frugiperda, to assess the efficacy of insecticides that readily available and commonly used by farmers for the control of S. frugiperda, and to establish the reliability on injury sign observed on maize crop to determine the appropriate insecticide to apply for effective control of the pest. The study on influence of altitude showed that there was significant difference among location in FAW abundance (p < 0.001). At low altitude SUA, the mean FAW abundance was high (24 per trap) compared to medium (9 per trap) and high altitude (7 per trap), Mgeta and Nyandira respectively. The study on response of S. frugiperda larval stages to selected insecticides under the laboratory and screen house experiments showed significant variation (p < 0.001) in time taken to cause 50% and 100% mortality. In laboratory, Duduba 450 EC and Ninja plus 5EC caused 100% mortality at 48 hours after treatment (HAT). Thunder 145 OD was a fourth most effective with 79.05% mortality in 48HAT. In screen house varied effectiveness were significantly (p < 0.001) recorded among insecticides with Multi Alpha plus 150 EC causing 100% mortality to all larval instars followed by Thunder that caused 76.67% mortality 48 HAT. The field experiment conducted at Mikese to determine the right timing of insecticide application based on injury sign on maize crop suggested significant interactions (p < 0.001) between injury signs and larval development stages. Injury signs could be used in choosing insecticides that are effective against the respective S. frugiperda larvae stage. Thus, the findings from this study can be used in planning for insecticide-based management options for the control of S. frugiperda.

Ministry of Agriculture