Abstract:
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.
