Predicting abundance and distribution risk of oriental fruit fly, Bactrocera dorsalis (Handel) in India based on CMIP6 projections linked with temperature-driven phenology models

Abstract

The Oriental fruit fly, Bactrocera dorsalis (Handel), an important pest of horticultural crops, was studied at seven ecologically pertinent constant temperatures (15, 18, 22, 25, 29, 32, and 35 °C) under a photoperiod of 12:12 h L:D with a relative humidity of 60 ± 10 % to establish its temperature-based development. The study was incepted to devise temperature-driven phenology models and to analyze the abundance and distribution risk of B. dorsalis in India based on CMIP6 projections based on the model outcomes. Using the Insect Life Cycle Modelling software, B. dorsalis process-based phenophases models were linked with three global climate models (GCMs) and two climate change scenarios (SSP1-2.6 and SSP5-8.5). The results revealed that the lowest temperature threshold (LTT) for the development of the egg, larva, pupa, male, and female of B. dorsalis were 9.8, 6.9, 9.7, 14.2, and 14.3 °C, respectively. The maximum number of females per female (net reproductive rate, R₀) (385.738 ± 7.62) and individuals per female (808.987 ± 13.409) (gross reproduction rate, GRR) per generation was succeeded at a constant temperature of 26 °C. At 29 °C, the maximum females per female (0.164 ± 0.0006 per day) (intrinsic rate of increase, r_m) and lowest doubling time (Dt) (4.22 ± 0.02 days) was noted. Temperatures between 26 and 29 °C were optimum for B. dorsalis survival, growth, and multiplications, leading to less generation time and increased population potential. The distribution and abundance indices projected for current climates (1970–2000) successfully fit the identified dispersal areas of B. dorsalis in India. The projections under the changing climates in India indicated that increase in temperature in future climate for B. dorsalis will be less suitable (∼65 %) for very high establishments (0.8–1.0 establishment risk index) but an increase in abundance and damage potential (16.48–71.39 %) is expected based on increased activity, and generation risk indices. In conclusion, the predicted abundance and damage potential suggest that B. dorsalis India will pose a considerable risk to horticultural crops in future climate scenarios. The study results offer important baseline data for developing the strategies of B. dorsalis management and phytosanitary actions at particular, local, and national levels in India.