The assistance and interest of Mr A. Dennis during this study is much appreciated. We would like to thank Dr D. G. Campion, Centre for Overseas Pest Research, ...
Bull. ent. Res. 72, 709-716 Published 1982
709
Species diversity and abundance of Dacus (Diptera: Tephritidae) in five ecosystems of Penang, West Malaysia TAN KENG-HONG and LEE SOO-LAM
School of Biological Sciences, Universiti Sains Malaysia, Penang, West Malaysia
Abstract Dacus dorsalis Hend. infested eleven, D. cucurbitae Coq. five and D. umbrosus F. two of the eighteen common fruits and vegetables grown in Penang, West Malaysia. D. tau (Wlk.) infested bacang (Mangifera foetida), D. caudatus F. chilli (Capsicum annuum) and D. frauenfeldi Schin. water guava (Eugenia javanica), together with D. dorsalis. Pomelo (Citrus grandis) was found infested for the first time by D. cucurbitae. No flies were trapped using Capilure and trimedlure as baits. Cue-lure attracted D. caudatus, D. cucurbitae, D. frauenfeldi, D. occipitalis (Bez.) and D. tau. Methyl eugenol attracted D. dorsalis and D. umbrosus. Dorsalure was less attractive to D. caudatus and D. dorsalis than cue-lure and methyl eugenol, respectively, but it was equally attractive to D. frauenfeldi as cuelure. Using traps baited with cue-lure or methyl eugenol in five ecosystems, the highest numbers of males of D. dorsalis, D. umbrosus, D. frauenfeldi and D. caudatus trapped were from a village, on a vegetable farm for D. cucurbitae, and D. occipitalis was only caught in a forest. Analysis showed that for each species of Dacus the difference between ecosystems was highly significant. The few examples caught in grassland were probably migrants.
Introduction Some species of Dacus are serious economic pests of fruit and vegetables in tropical, subtropical and temperate regions of the world (Bateman, 1972; Newell & Haramoto, 1968; Nishida & Bess, 1957). In Malaysia and Singapore, about 20 species of Dacus have been recorded (Hardy & Adachi, 1954; Hardy, 1973). Male attractants have been used successfully to suppress or eradicate fruit-flies. Methyl eugenol was used to eradicate the oriental fruit fly, D. dorsalis Hendel, in the Marianas Islands (Steiner et al., 1965). Cue-lure was effective in suppressing D. cucurbitae Coquillett (Cunningham & Steiner, 1972; Iwahashi et al., 1975). Attractant traps are suitable for detection and ecological studies (Harris et al., 1971; Fletcher, 1974). In this paper, the species diversity and relative abundance of species of Dacus are described in five ecosystems in Penang Island, West Malaysia, using traps with different attractants. The fruit hosts of the various species in Penang were also investigated. Materials and methods Attractants The following attractants were used: (a) Capilure * mixture of trimedlure and extender; * Proprietary products of International Pheromones Ltd.; no chemical details or proportions available.
710 (b) Cue-lure (c) Dorsalure * (d) Methyl eugenol (e) Trimedlure
TAN KENG-HONG and LEE SOO-LAM
4-(p-acetoxyphenyl)butan-2-one; mixture of methyl eugenol (higher proportion) and cue-lure; exact proportion unknown; 4-allyl-l,2-dimethoxybenzene; and tert-butyl 4(or 5)-chloro-2-methylcyclohexane-carboxylate.
Attractant traps A 1-ml sample of attractant was pipetted on to two cotton buds in each modified Steiner plastic trap used in the field. Precautions were taken to prevent crosscontamination, and all glassware was rinsed in a chloroform: methanol mixture (2:1 v/v) (Tan, 1973) and plastic materials were incinerated after use. Selected ecosystems Five different ecosystems in different localities were selected in Penang Island, and their approximate areas are indicated in Fig. 1:
Fig. 1.—Selected ecosystems in Penang Island. (F = Forest reserve; G = Grassland; O = Orchard; V = Village; VF = Vegetable farms.) (a) Forest reserve with a wide variety of trees representing a natural undisturbed ecosystem. (b) Grassland: rice-fields in abeyance where a large variety of weeds and grasses but no trees were found. (c) Orchard, mainly of papaya (Carica papaya) with some chilli (Capsicum annuum), jackfruit (Artocarpus heterophyllus) and water guava (Eugenia javanica); located
DACUS SPP. IN MALAYSIA
711
in Tanjong Bunga. For species-specificity studies of different attractants another similar orchard was used. (d) Village densely populated with a wide variety of fruit trees: starfruit (Averrhoa carambola), jackfruit, soursop (Annona muricata), guava (Psidium guajavd), water guava, chilli, etc. (e) Vegetable farms where most leafy vegetables, especially cucumber (Cucumis sativus), bittergourd (Momordica charantia) and chilli are grown; located at Relau in the centre of the island. Species of Dacus from infested fruits Infested fruits were collected randomly from the various ecosystems. Each fruit was placed on sterilised sand moistened with distilled water in a plastic container covered with fine wire mesh. Pupae were isolated after larvae emerged from the fruit. The adults were identified from keys and descriptions in Hardy (1973). The immature stages were kept at room temperature (27-29°C) and 80 ± 5 % RH. For each type of fruit, at least three infested fruits were collected from any locality. Specificity of attractants and comparison of species predominance in different ecosystems Five different attractant traps were set up in each ecosystem so that they were at least 30 m apart. Each trap was hung about 2 m above the ground from a support smeared with grease to prevent removal of dead flies by ants. Fruit-flies trapped in each trap were collected weekly, and the traps were rotated so that each one would have been positioned in five trap sites over a period of five weeks. The flies from each trap were separated according to species and counted. Where a species was attracted to more than one trap, a comparison of means was performed. Catches in different ecosystems using cue-lure and methyl eugenol In another experiment, after the main fruit season, for 18 weeks between September 1978 and January 1979, two traps baited with cue-lure and two with methyl eugenol were placed in the centre of each ecosystem and at least 30 m apart. Fruitflies from each trap were removed weekly, sorted and counted. Every four weeks, the cotton wool in each trap was renewed with addition of fresh attractant. Results Fruit infested by Dacus spp. Details of the infestation of 18 fruits are given in Table I. Eleven of the fruits were infested by D. dorsalis. Pomelo was found infested for the first time by D. cucurbitae. Species of Dacus attracted to the various baits A total of seven species of Dacus was attracted to three of the five attractants used (Table II). Cue-lure attracted five species, methyl eugenol two, and Dorsalure three. Capilure and trimedlure did not attract any species. Catches with dorsalure and cue-lure or methyl eugenol The mean number of males of D. dorsalis trapped using methyl eugenol as attractant was significantly higher than that caught using Dorsalure in all localities where it was caught in good numbers (Table III). A similar result was obtained for males of D. caudatus F. trapped in the orchard. However, the mean number of D. frauenfeldi Schiner males caught in traps baited with Dorsalure was not significantly different from that caught in traps baited with cue-lure. No adults of D. cucurbitae were caught in Dorsalure-baited traps, even on the vegetable farm.
712
TAN KENG-HONG and LEE SOO-LAM
TABLE I.
Fruits infested by the different species of Dacus in Penang Fruit
Common name Bachang Banana Chilli Guava Kuini Mango Papaya Soursop Starfruit Water guava Yellow sentul Bitter gourd Cucumber Long bean Pomelo Water melon Cempedak Jackfruit
TABLE SPECIES D. D. D. D. D. D. D.
Dacus spp. found infesting fruit
Scientific name Mangifera foetida Musa paradisiaca Capsicum annuum Psidium guajava Mangifera odorata Mangifera sp. Carica papaya Annona muricata Averrhoa carambola Eugenia javanica Sandoricum indicum Momordica charantia Cucumis sativus Vigna unguiculata Citrus grandis Citrullus lanatus Artocarpus integer Artocarpus heterophyllus
D. D. D. D. D. D. D. D. D. D. D. D. D. D. D. D. D. D.
dorsalis, D. tau dorsalis dorsalis, D. caudatus dorsalis dorsalis dorsalis dorsalis dorsalis dorsalis dorsalis, D.frauenfeldi dorsalis cucurbitae cucurbitae cucurbitae cucurbitae cucurbitae umbrosus umbrosus
II. Species of Dacus caught in traps baited with the different attractants Capilure
Cue-lure
Dorsalure
Methyl eugenol
Trimedlure
caudatus cucurbitae dorsalis frauenfeldi occipitalis tau umbrosus
Catches in different ecosystems with methyl eugenol and cue-lure In traps baited with methyl eugenol, males of D. dorsalis were caught in large numbers in the village, with slightly fewer in the orchard (Table IV). A fairly high number was caught in the forest but few on vegetable farms (where the lower number in 1978-79 compared with that early in 1978 was probably due to the absence of chilli in the former season) and only occasional ones in grassland. No males of D. umbrosus F. were caught in grassland or on vegetable farms, and the largest numbers were trapped in the orchard and village. With cue-lure as attractant, higher numbers of D. cucurbitae males were caught on vegetable farms than in village and orchard; none was trapped in the forest and only three in grassland (Table V). D. frauenfeldi males were trapped mainly in the village but also in the forest and orchard. D. caudatus males were caught only in village and orchard, while D. occipitalis (Bezzi) was trapped only in the forest. In all instances of catches of males with cue-lure, there was no difference in the numbers caught between the two traps in each locality. Analysis of variance for those ecosystems which had more than 1 male/trap per week or less than 35% empty traps in a total of 36 trap-weeks over 18 weeks, showed that for every species the number of males trapped between ecosystems was highly significant (Table VI). The weekly numbers caught in one ecosystem did not differ significantly. It was confirmed that the highest numbers of males of D. dorsalis, D. umbrosus, D. frauenfeldi and D. caudatus were caught in the village and those of D. cucurbitae on the vegetable farms. Discussion D. dorsalis was shown to be the predominant species of Dacus and infested many
Mean ±s.e. P*
Forest reserve Mean ±s.e. P*
Orchard
Vegetable farms Mean ±s.e. P*
n >»••
'
>o 2
per week.
21 14 : 4
0 •8
11363- 2
Village Meanis.e. P*
III. Weekly mean catches of males of Dacus spp. in traps baited with Dorsalure and methyl eugenol or cue-lure in five ecosystems f over five weeks early in 1978
D. dorsalis QC 1 1 180 455- 6 Methyl eugenol 55 • 2 l\\*
