Arthropod diversity and biology and management of gall wasp (Leptocybe invasa Fisher & La Salle) in Eucalyptus
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Date
2023
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Punjab Agricultural University
Abstract
Leptocybe invasa Fisher & La Salle is an important pest of Eucalyptus throughout the world and cause damage to young foliage of Eucalyptus by causing serious injury. In the present study, experiments on arthropod diversity in Eucalyptus, incidence of L. invasa in different agroclimatic zones of Punjab, seasonal abundance, biology of L. invasa, screening of Eucalyptus genotypes against L. invasa and management of L. invasa using botanicals was conducted. The arthropod fauna from Order Coleoptera, Lepidoptera, Diptera, Hymenoptera, Hemiptera, Isoptera, Dermaptera, Orthoptera, Araneae, Isopoda, Collembola and Diplura were recorded in Eucalyptus plantation. During survey, among different agroclimatic zones, highest per cent infestation was observed in submountainous zone followed by central zone and least per cent infestation was recorded in south western zone. Percentage infestation was more in nursery plants as compared to roadside and field plantations. Parasitization by Quadrastichus mendeli Kim & La Salle and Megastigmus viggianii Narendran & Sureshan was recorded in all agroclimatic zones of Punjab. Number of galls and adults were more in September, October and April as compared to other months. Minimum infestation was observed in months of December, January and February. Statistically significant correlation and regression values indicate that population of L. invasa and number of galls fluctuate with weather parameters. Life cycle of L. invasa was completed in 85-150 days depending upon the season. In winter, the larvae and pupae hibernate that increase the life cycle of L. invasa during cold months. Adult longevity was significantly higher when adults were fed on honey solution followed by only water and young Eucalyptus leaves, however, adult longevity was lowest when adults were kept without food. The gall development induced by L. invasa was studied in Eucalyptus clones having different levels of susceptibility to gall wasp attack. It was observed that in susceptible clones, adult emergence was recorded from both green and pink coloured galls, however, in resistant clones adults emerged from green galls. Stage 1 (tissue disruption) was longer in resistant clones than in the susceptible clones, however stage 5 (exit hole) was longer in susceptible clones. Size of gall and number of emergence holes per gall were more in susceptible clones as compared to resistant clones. Among different genotypes screened against L. invasa, 25 were categorised as most resistant, 1 moderately resistant, 1 moderately susceptible and 11 most susceptible. The severe deformations in vascular bundles and parenchyma in the damaged midrib tissue were observed due to formation of the galls. Activity of biochemical compounds (protein, phenol, flavonoid, chlorophyll, carotenoid, DPPH activity) and defence related enzymes was high in resistant clones as compared to susceptible clones. The trend was opposite for total soluble sugars content, which was highest in susceptible clones and lowest in resistant clones. Per cent reduction of number of galls per plant and galls per leaf was highest in neem oil (50 ml/l) followed by neem seed kernel powder, karanj oil, castor oil and minimum in home made neem extract.
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Saloni (2023). Arthropod diversity and biology and management of gall wasp (Leptocybe invasa Fisher & La Salle) in Eucalyptus (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.