Diversity and population dynamics of mango fruit fly bactrocera spp (Diptera: Tephritidae)

Abstract

The study entitled “Diversity and population dynamics of Bactrocera spp. (Diptera: Tephritidae)” was conducted at the Department of Entomology, College of Agriculture, Padannakkad during 2021-2022. The main objective of the study was the documentation of species complex, varietal preference and population dynamics of Bactrocera spp. infesting mango in the Instructional Farm I, College of Agriculture, Padannakkad. Surveillance of fruit flies for a period of one year from 17-09-2021 to 16-09-2022 was carried out using bottle traps with methyl eugenol as the lure. A total of 10,546 individual fruit flies were trapped during the surveillance period of which major percentage was B. dorsalis. Four species of fruit flies viz. Bactrocera dorsalis, B. zonata, Zeugodacus tau and Z. cucurbitae were identified from the population collected in that order of dominance. Out of 10,546 total fruit flies captured 10,332 adults were identified as B. dorsalis, accounting for 97.97% of the population being the dominant fruit fly in the area, 199 number of fruit flies (1.89%) were identified as Zeugodacus cucurbitae, nine fruit flies (0.09%) were identified as B. zonata, and six fruit flies (0.06%) were identified as Z. tau. The highest weekly population of fruit flies was recorded in the 14th Standard Meteorological Week of 2022 (02-04-2022 to 08-04- 2022), with a population of 793 fruit flies and the lowest population in 50th SMW (10- 12-2021 to 16-12-2021), with only one fruit fly. The average monthly population was recorded highest in May with a population of 667.5 flies per month and lowest in December with a population of 16 flies per month. Population parameters of fruit flies such as species richness was found to be 0.32, Simpson dominance index as 0.04, Shannon Weiner diversity index as 0.11 and evenness index as 0.42. Population of fruit flies during the surveillance period of one year had a significant positive correlation with minimum temperature (+0.354). Population of fruit flies during the fruit availability i.e., from April to June had a significant positive correlation with minimum temperature +(0.805), and a significant negative correlation with soil temperature (-0.512). Maximum temperature (-0.329) and wind speed (-0.192) had a negative correlation with population of fruit flies and a positive correlation with rainfall (0.204). Both field and laboratory evaluations were carried out to determine the varietal preference of Bactrocera dorsalis for ten different mango varieties, viz., Phirangiladuva, Kalapady, Neelum, Bangalora, Bennet Alphonso, Mundappa, Banganappalli, Himayuddin × Neelum, Gomanga, and Kuttiattoor mango during the peak period of infestation i.e., from April to June. Natural infestation showed a significantly lower number of egg laying in fruits of Neelum, maggot development in the pulp of Bennet Alphonso and Neelum and adult emergence from the fruits of Himayuddin X Neelum, Kalapady and Bennet Alphonso respectively. Kuttiattoor mango recorded significantly higher number of eggs laid, maggot developed and adult emergence from natural incidence. A total number of 1934 adults emerged from naturally infested varieties were identified as B. dorsalis. Laboratory evaluation of preference of B. dorsalis showed non preference for egg laying, maggot development and adult emergence from mango varieties like Bennet Alphonso, Kalapady, Neelum, Mundappa, Himayuddin X Neelum, and Kuttiattoor mango. Number of eggs laid, maggots developed and adult emergence was significantly higher in Gomanga, Banganappalli, and Gomanga and Bangalora varieties of mango respectively in laboratory condition. Naturally fallen mangoes of six varieties viz., Banganappalli, Phirangiladuva, Kalapady, Neelum, Bangalora and Mundappa collected from IF 1 recorded significantly lower number of maggot development in the Kalapady variety. Phirangiladuva and Banganappalli varieties recorded significantly higher numbers of maggot development. Screening of mango varieties for fruit fly resistance showed that variety Neelum is highly resistant and variety Kalapady is resistant to fruit fly infestation. Correlation between morphological characters of fruit and number of eggs laid in fruits showed that peel thickness had a significant negative correlation (-0.674). Correlation between biochemical characters and maggot population, adult emergence and percent infestation of fruits showed significant negative correlation with ascorbic acid content (-0.67, -0.77, -0.66) and crude fibre content (-0.86, -0.82, -0.59) and significant positive correlation with total sugar content (0.71, 0.70, 0.84). Total phenol content, flavonoid and titrable acidity had a negative correlation. Varietal preference of B. dorsalis suggested that Neelum and Kalapady varieties showed a significant resistance. Morphological and biochemical characters of fruits are significantly related with resistance of mango varieties against B. dorsalis and therefore, can be used as marker traits in further breeding programmes to select resistant varieties.