Abstract
Fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), is a major pest of maize. Yield losses between 30 and 70% in the Americas and between 11 and 100% in Africa have been reported. Little information exists on the effect of pest damage during different plant growth stages on yield loss. Previous studies showed that insecticide applications at weekly intervals did not always provide a yield gain comparable to only a single or two well-timed applications. In this study, we completed four field trials under high natural pest pressure. Treatments consisted of different regimes of insecticide applications that provided protection against damage during different growth stages. In one trial, the mean incidence of infested plants was 65%, and the yield benefit gained from four insecticide applications was 32.6%. The other three trials had 16 treatments which were divided into two spray sequences to protect plants against FAW damage for different lengths of time, between early vegetative stages and tasseling. Yield losses were 41.9, 26.5 and 56.8% for the three respective trials if no insecticides were applied. Yield loss of plants protected during earlier growth stages was significantly lower than that of the treatments which provided protection during later growth stages. More than three spray applications generally completed did not provide further yield gains. Plants that were protected more during early growth stages yield higher than plants protected during later growths stages.
Highlights
Fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), infests maize during all plant growth stages, with infestation during vegetative stages leading to serious leaf-feeding injury, while late infestations lead to ear damage [1,2,3,4,5]
The lowest yields were obtained from plots that received none or only a single insecticide application, at either 1 week after seedling emergence (WAE)
A similar observation was made by Baudron et al [32], who reported that the FAW infestation levels on smallholder farmers’ fields in Zimbabwe ranged between 32 and 48%, and estimated yield loss to be 11.6%, which is lower than that reported in many other studies conducted in the Americas
Summary
Fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), infests maize during all plant growth stages, with infestation during vegetative stages leading to serious leaf-feeding injury, while late infestations lead to ear damage [1,2,3,4,5]. This damage results in both quantitative and qualitative losses [6,7,8]. Yield losses suffered by maize are mostly dependent on the plant tissue type where larval damage occurs [3], with infestations during the vegetative growth stages leading to extensive foliar damage.
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