BIOLOGICAL CONTROL OF PARTHENIUM HYSTEROPHORUS L.: POST RELEASE ECOLOGICAL IMPACT BY INTRODUCED BEETLE, ZYGOGRAMMA BICOLORATA PALLISTER IN J and K
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Date
2013
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Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu
Abstract
Studies were conducted to understand the ecological adaptability, insect-plant interaction for enhancing the biological potential, physiological and biochemical basis of diapause and its possible manipulation and to evaluate post release ecological impact of Zygogramma bicolorata Pallister on early flushes of Parthenium hysterophorus L. in Jammu region. It was revealed that the beetle undergo ecological adaptability in term of reproductive and other biological parameters, viz. fecundity, longevity (male/female) per cent hatching, pupation, adult emergence and survival. The beetles collected from Coimbatore exhibited significantly lower diapause and higher survival after termination of diapause and started egg laying eggs within 6-7 days of termination as compared to 11-13 days in other populations. The threshold temperature for the optimum development of beetle was found to be 10 - 35°C. However, when adults were exposed to extreme lower (-5°C) and higher (45°C) temperature that could prevail in Jammu region, populations collected from Coimbatore outperformed local populations. These findings suggested that local populations belonging while being adapted to local conditions could have to divert some energy for physiological compensation for overcoming environmental stress. Frequency of Oocytes (mature and immature) was significantly higher in non-diapausing females. However, flight muscle degeneration and oviposition cessation was significantly more in diapausing adult beetles. Mean weight of total proteins, carbohydrates and lipids varied significantly in diapausing and non-diapausing adults. Although, natural impact of beetle on this weed was significant over the beetle exclusion sites but the bio-suppression of weed was greatly enhanced when the natural population of the beetle was supplemented with augmentative releases. The release of adult beetle @10 beetles/m<sup>2</sup> in the 2nd fortnight of February followed by 15th day after 1st release @ 5 beetles/m<sup>2</sup> in augmented sites for three consecutive years (2008-2011) led to increased reduction in flower biomass (36%) and soil seed bank (60%) over naturally infested sites. The diversity and evenness of species varied significantly with Zygogramma bicolorata infestation levels and highest mean abundance of diversity in the high beetle intensity sites. Parthenium populations were reduced by more than 90% and replaced by other species, among which Cassia tora dominated in subsequent years. The competitive ability of grasses and other weeds showed that Cyanodon dactylon, Cyprus rotundus, Xanthium strumarium, Cannavis sativa, Cassia tora, Cassia auriculata and Cassia occidentalis significantly out competed Parthenium in augmented release sites in comparison to two other sites. Encouraging vegetative competition could further enhance the negative effects of defoliation.
Key words: Biological control, Zygogramma bicolorata, reproductive attributes, biochemicals, augmentation, post release ecological impact.
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