Leaf damage by Spodoptera frugiperda J. E. Smith (Lepidoptera: Noctuidae) and its relation to leaf morphological traits in maize landraces and commercial cultivars.
The fall armyworm Spodoptera frugiperda J. E. Smith (Lepidoptera: Noctuidae) is one of the most damaging pests of maize production in tropical areas. Leaf damage caused by its feeding depends greatly on chemical and physical leaf traits. In the present study, the degree of leaf damage by S. frugiperda in three maize landraces (Chimbo, Elotillo and San Pableño) and three commercial cultivars (Vs-536, Dekalb 390 and Impacto) was evaluated in a naturally infested field experiment. Morphological leaf traits were measured and associated with the degree of leaf damage at three sample dates 15, 30 and 45 days after emergence when developmental stages of plants were V5, V8 and V12, respectively. Overall, maize landraces showed lower leaf damage than commercial cultivars. Particularly, the landraces Chimbo and Elotillo had the lowest leaf damage, calculated by the area under the severity progress curve. Morphological leaf traits varied significantly (p < 0.05) among maize genotypes, but their patterns were not consistent in all sample dates. Pearson correlation analysis showed that leaf damage was negatively correlated with leaf toughness (rs=−0.45, p < 0.001) at the developmental stage V12 and positively correlated with trichome density (rs=0.44, p < 0.001) at developmental stage V8.