Scale insect Melanaspis glomerata (Green) (Homoptera: Diaspididae) in world collection of Saccharum spontaneum L.

Abstract

The status of the sugarcane scale Melanaspis glomerata (Green) (Homoptera: Diaspididae) in an international collection of Saccharum spontaneum L., maintained as a part of world sugarcane germplasm at the ICAR-Sugarcane Breeding Institute Research Centre, Kannur, Kerala state, India, was examined in 2016 and 2017. The scale appeared in May coinciding with cane formation and the infestation started increasing during the post-monsoon period (September–December) which continued until harvest (January). Scale infestation varied widely among the accessions of S. spontaneum in the two experimental years. Infestation rates (cane basis) were significantly higher in 2017 than in 2016. Infestation rate and intensity (internode basis) were positively correlated in 2017. When the 79 accessions examined were grouped into three categories on the basis of higher infestation rate in the two study years, 21 (26.6%) were placed in least susceptible, 38 (48.1%) in moderately susceptible and 20 (25.3%) in highly susceptible categories. The highest infestation rate (100.00%) was recorded in the accession US 56–10-14 and lowest (2.94%) in SES 106B; two accessions, namely SH 61–4-1 and SH 61–4-3 were totally free from infestation. Non-parametric analysis of infestation parameters indicated higher intensity in foreign than Indian accessions. Plant height was positively and number of internodes negatively correlated with infestation rate in the low infestation year (2016). Also, infestation rate (2016) was significantly higher in accessions with inconspicuous wax band than those with prominent wax band; intensity (2017) was significantly highest in accessions with conoid internode shape in comparison with cylindrical and obovate shapes. However, canopy and leaf characteristics did not influence attack rates.