Biology, population dynamics and trapping of Zeugodacus (Zeugodacus) tau (Walker) (Diptera: Tephritidae)
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Date
2019
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Dr. Rajendra Prasad Central Agricultural University, Pusa, Samastipur (Bihar)
Abstract
Results of the experiments conducted to study the biology, population dynamics and trapping of Zeugodacus (Zeugodacus) tau (Walker) are presented. Pre-oviposition period was 11-13 days and female laid 6-12 eggs/ day. Average incubation period was 1.21 ± 0.06 days and per cent hatchability of eggs was 80.0 ± 7.07 per cent. Average larval duration was 6.60 ± 0.15 days and larval survival was 75.00 ± 12.80 per cent. Average pupal duration was 7.45 ± 0.22 days while percentage of adult emergence was 70.00 ± 8.10 per cent. Sex ratio (male: female) of emerged flies was 1:1.27 and life-cycle was completed in 15.26 ± 0.23 days. Egg was elongated, elliptical, glistening white, 1.3-1.4 mm long and 0.22-0.24 mm wide. Third instar larva ranged from 7.8-9.0 mm, anterior spiracles have 14-16 tubules while posterior spiracle with spiracular hairs arranged in dorsal and ventral bundles (with 14-18 hairs) and lateral bundles (with 5-9 hairs). Pupa exarate, 4.9-5.5 mm long, brownish or reddish-brown, with free appendages, encapsulated within a barrel-shaped puparium.
In adult, face yellow with two oval black spots; chaetotaxy reduced. Three pairs of equal sized inferior orbital (lower fronto-orbitals) setae; one pair superior orbital (upper fronto-orbitals) setae. Ocellar, postvertical setae absent, median and lateral vertical setae present. Scutum brownish-grey, with 3 postsutural yellow vittae; scutellars 2 pairs. Wing infuscations light brown, costal band continuous and expands into a large dark brown spot at apex. Crossvein R-M oblique, both R-M and dm-cu crossveins without spot. Anal band light brown that fills cell bcu and part of cell cu1. Abdominal tergite 3 of male with pecten on each side and yellow to orange-brown; with lateral black markings; terga III-V with a black T pattern while anterolateral corners of terga IV and V with broad black markings. Male genitalia and female ovipositor have been described and illustrated.
Z. tau adults were available throughout the experimental period except when temperature was very low. It was maximum during 20th and 25th standard weeks, i.e.
79.50 and 56.50 flies/ trap/ week, respectively and no fly was captured during 1st and 2nd standard weeks of 2019. Thereafter a gradual increase in fly population was observed till 13th standard week of 2019. During May, 2018 fly population was maximum (42.65 flies/ trap) followed by June, 2018 (25.81 flies/ trap) and during subsequent months of 2018 the fly population reduced significantly up to September, 2018. Z. tau population had a positive and significant correlation with maximum and minimum temperature while negative and non-significant correlation was observed with maximum and minimum RH. For maximum and minimum temperatures, values of ‗r‘ were 0.426** and 0.296*, respectively. For RH values of ‗r‘ were -0.272NS and -0.013NS, respectively. Rainfall also showed positive but non-significant correlation with fly population and value of ‗r‘ was 0.097NS. The cumulative effect of weather factors on population fluctuation of Z. tau was 27 per cent (R2= 0.271).
Maximum flies were annihilated during 20th standard week of 2018 in treatment with protein bait (79.50 flies/ trap/ week). The rate of male annihilation in treatment with molasses as bait and without bait did not differed significantly. In all treatments, 10094 males of Z. tau were annihilated during the period of experimentation. Mean numbers of flies/ trap annihilated in different treatments were: 400.25 (no bait), 733.25 (protein bait), 503.00 (jaggery as bait), 480.75 (fruit pulp as bait) and 406.25 (molasses as bait), respectively.
In colour traps maximum flies were annihilated during 19th standard week and the order of trap based fly catches (flies/trap/week) was: yellow (73.75) > orange (34.00) > transparent (30.25) > green (11.75) > red (7.75). The captures of Z. tau were significantly greater in yellow trap during May, 2018 (215.50 flies/ trap/ month) followed by orange trap (131.50 flies/ trap/ month). In all coloured bottle traps, 9307 males of Z. tau were annihilated during the period of experimentation. Mean number of flies/ trap annihilated in different coloured bottle traps during experimental period were: 180.25 (red), 708.25 (yellow), 522.00 (orange), 402.75 (green) and 513.50 (transparent), respectively.
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