Browsing by Author "B. J. Nirmal Kumar"

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    Field detection, molecular characterization and biology of the tea tortrix, Homona coffearia Neitner (Lepidoptera: Tortricidae) on Cocoa (Theobroma cacao. L) from India
    (2024) Madhu T. N.; Saneera E. K; R. Thava Prakasa Pandian; Bhavishya; Nagaraja N. R; M. Chaithra; S. Elain Apshara; B. J. Nirmal Kumar; Diwakar Y; Suchithra M; Rajesh M. K; Vinayaka Hegde
    Cocoa (Theobroma cacao. L) is an important commercial crop widely cultivated in humid tropical regions; however, its production faces various constraints including insect pests. The survey conducted in 2022–2023 found significant damage to cocoa nurseries and fields caused by the larvae of H. coffearia. The caterpillars web the young leaves, feeds within the sheltered nests and affects the crop canopy. The percent incidence was 27.55 ± 1.81% in the nursery and 43.77 ± 3.42% in open fields. A detailed morphological examination and molecular characterization using the mitochondrial cytochrome c oxidase I (COI) gene confirmed the identity of the pest as H. coffearia. The study also documented the key biological parameters of H. coffearia on cocoa under laboratory conditions. The life cycle from egg to adult was completed in about 49 ± 2.32 days. Female moths laid an average of 106 ± 3.48 eggs, which hatched into larvae that underwent five instars before pupation. Both the larval and pupal stages lasted around 27.69 ± 0.72 and 7.72 ± 0.17 days respectively. To our knowledge, this is the first report of the tea tortrix, H. coffearia infesting cocoa in India. As a polyphagous pest, the ability of H. coffearia to adapt and feed on new host plants like cocoa poses a significant threat to cocoa production. The findings of this work highlight the need for further research on the population dynamics, damage potential and management strategies for this emerging pest in cocoa ecosystems.
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    Laboratory rearing of tea mosquito bug, Helopeltis theivora Waterhouse (Hemiptera: Miridae) on cocoa (Theobroma cacao L.)
    (2024) T. N. Madhu; E. K. Saneera; R. Thava Prakasa Pandian; Bhavishya; M. Chaithra; M. Sujithra; N. R. Nagaraja; B. J. Nirmal Kumar; S. Elain Apshara
    Tea mosquito bug (TMB), Helopeltis theivora is a most serious pest on cocoa worldwide that inflicts huge economic losses under epidemic situations. Laboratory colonies are necessary to perform year-round research to develop suitable management strategies for this pest. This study aimed to establish a population of TMB on suitable cocoa-feeding substrates under laboratory conditions. We used green cocoa pods and tender shoots as a food substrate and compared the biological parameters of H. theivora between them. The adult females preferred to lay more eggs on pods (32.20 ± 1.86 eggs/female) either singly or in a small group, and low fecundity was observed on shoots (20.75 ± 1.16 eggs/female). Meanwhile, egg hatching was highest on pods (92.48 ± 2.91%) than on shoots (74.08 ± 3.73%). This pest consists of five nymphal instars and the total nymphal duration was 13.53 ± 1.26 and 14.73 ± 0.85 days on pods and shoots, respectively. In addition, the per cent survival of H. theivora was highest on pods (78.66 ± 3.46) and lowest on shoots (51.85 ± 2.33). Significant differences were recorded in adult longevity and the mean life span of males and females were 13.17 ± 1.58 and 16.63 ± 1.64 days on pods; 11.10 ± 1.41 and 14.36 ± 1.53 days on shoots, respectively. Further, females lived longer than males in both substrates. Although, TMB will survive both on pods and tender shoots; rearing on pods could be more suitable and reliable to establish a sizable population of H. theivora under laboratory conditions.