Biophysical Factors Influencing Fall Armyworm Damage in Maize: Insights from Morphological Traits and Cob Characteristics

Aims: Influence of different morphological (biophysical) parameters on the incidence of fall armyworm. Sample: All the observations on plant morphological traits and collection of plant samples for biochemical analysis were made at two respective crop growth stages of maize i.e., five leaf stage (V5) and at tasseling stage (VT) which coincides at 30 and 60 days after sowing respectively. Whereas, cob samples were collected at reproductive stage of the crop. Study Design: Randomized Complete Block Design (RCBD). Place and Duration of Study: Zonal Agricultural Research Station (ZARS), V. C. Farm, Mandya duringKharif2020-21. Methodology: The plant height, leaf length and leaf width of the crop was recorded with the help of a measuring tape. The stem diameter of the crop was recorded using Vernier. The trichomes of a leaf were counted under a binocular microscope from 1 cm2 area of a leaf. The number of stomata on leaves was counted by using compound microscope from an area of 1 mm2 of a leaf. The leaf colour was recorded using 1 to 4 colour index. The length of central spike of a tassel was recorded with the help of measuring tape. The height of the cob above the soil level was recorded with the help of measuring tape up to the node position of cob at silking stage. The cob length and cob diameter were measured using measuring tape and vernier calipers respectively and then the mean was calculated. Results: The morphological traits like plant height (0.56* & 0.10) and leaf length (0.46* & 0.04) are positively correlated, whereas, leaf width had a positive (0.63**) and negative correlation (-0.23) with leaf damage at 30 and 60 DAS, respectively. Stem girth (-0.33 & -0.67**) and trichome no. (-0.71** & -0.60**) were negatively correlated, leaf color had a negative (-0.05) and positive (0.32) correlation, no. of leaves had a positive (0.43) and negative correlation (-0.06) at 30 and 60 DAS, respectively, whereas, stomatal density on upper (-0.33) and lower (-0.32) leaves was negatively correlated with leaf damage at 30 DAS. The biophysical parameters in cob samples like tassel length (-0.144) had negative, cob length (0.561*) had positive, cob diameter (-0.47*) had positive and ear height (-0.161) had negative association with leaf damage rating. Conclusion: Morphological traits of maize inbreds influence fall armyworm infestation. At 30 DAS, infestation positively correlated with plant height, leaf length, leaf width, but negatively with trichomes. At 60 DAS, infestation correlated negatively with trichomes and stem girth positively with leaf color.