Ceratitis Spp.) (Diptera: Tephritidae),Pests of Fruit Crops on Réunion Island

Proceedings of 6th International Fruit Fly Symposium 6–10 May 2002, Stellenbosch, South Africa pp. 67–69

Comparative study of the developmental biology of three species of fruit flies (Ceratitis spp.) (Diptera: Tephritidae),pests of fruit crops on Réunion Island

Pierre-François Duyck*, Serge Quilici & Serge Glénac CIRAD Réunion, Pôle de Protection des Plantes, 7 Chemin de l’IRAT, 97410 Saint–Pierre, France

Fruit flies (Diptera: Tephritidae) are the most damaging pests on fruit crops on Réunion Island. Survival and development of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), the Natal fruit fly, C. rosa (Karsch) and the Mascarene fruit fly, C. catoirii Guérin–Mèneville, were compared at five constant temperatures from 15 to 35°C. The lower developmental threshold and the thermal constant were calculated using the temperature summation model. Survival and development of the species differed mainly in the larval stage and the ovarian maturation period, whereas few differences were found in the egg stage. C. rosa appeared to be better adapted to low temperatures than the other two species. C. catoirii had a low survival rate on the overall range of temperatures studied. The different responses of the three Ceratitis species at various tempera- tures may to some extent explain their distribution on the island. The results obtained will be used for optimizing laboratory-rearing methods. Furthermore, our data will be useful for construct- ing computer simulation models to predict the population dynamics of the three species of fruit flies.

INTRODUCTION The results should enable a better understand- Fruit flies (Diptera: Tephritidae) cause serious ing of their recorded distribution on the island damage on fruit and vegetable crops on Réunion and an optimization of rearing procedures in the Island (Indian Ocean). Three species of the genus laboratory. Ceratitis infest fruit crops there (Etienne 1982): the Mediterranean fruit fly, Ceratitis (Cera- MATERIALS AND METHODS titis) capitata (Wiedemann), abundant in dry The time required for 50% of individuals to areas, the Natal fruit fly, Ceratitis (Pterandrus) rosa complete the development of a particular stage Karsch, the most harmful species, very poly- was determined at the following constant temper- phagous and widespread on the island, from sea atures (±1°C): 15, 20, 25, 30, and 35°C. A photo- level up to an altitude of 1500 m, and the period of L12:D12 and a relative humidity of Mascarene fruit fly Ceratitis (Ceratitis) catoirii 80 ± 10% were provided in the environmental Guérin-Mèneville, an endemic species from the chambers. Mascarene Islands, found only in the moist areas The methodology was similar to that used for the of low altitude. study of the tomato fly, Neoceratitis cyanescens While numerous papers are available on (Bezzi) (Diptera: Tephritidae), by Brevault & Quilici C. capitata from work conducted in various (2000), using different cohorts of insects for each countries, C. rosa has been poorly studied despite particular stage. its economic importance in many African countries Egg stage. Egg stage duration was determined (Hancock 1989).The biology of C.catoirii is virtually by placing 100 randomly selected eggs (age unknown. <2 h) on moist filter paper in a Petri dish with a The relative importance of these species on fine brush. Eggs were observed every two hours Réunion depends on inter-specific competition, under a stereo-microscope to determine hatching. affected by intrinsic (biotic potential of the species) Larval stage. One hundred newly hatched larvae or extrinsic (climate, presence and abundance of (age <2 h) were carefully transferred into a the host plant) factors. container of artificial diet (Etienne 1973; unpubl.). This study aimed at specifying both the influ- About two days later, the larvae were transferred ence of the temperature on developmental time to a box containing a second artificial diet and and survivorship of the different immature stages bran, which was then placed inside a larger plastic and the ovarian maturation of these three species container, the bottom of which was covered by a in order to obtain data on their entire life cycle. layer of sand to allow pupation of jumping larvae.

*To whom correspondence should be addressed. Observations were performed three times a day E-mail: [email protected] by sifting the sand and recording the number of 68 Proceedings of the 6th International Fruit Fly Symposium

Table 1. Lower developmental threshold temperature (t ) and thermal constant (K ) for each developmental stage of Ceratitis capitata, C. rosa and C. catoirii.

tKR2 Species (°C) (D°)

Egg development C. capitata 11.6 28.1 0.99 C. rosa 9.8 35.3 0.98 C. catoirii 9.9 35.1 0.98 Larval development C. capitata 10.2 88.8 0.99 C. rosa 3.1 223.2 0.88 C. catoirii 8.9 126.5 0.99 Pupal development C. capitata 11.2 142.7 0.99 C. rosa 11.0 146.9 0.99 C. catoirii 9.2 194.0 0.99

pupae recovered. Pupal stage. As soon as pupation was completed, 100 pupae (age <2 h) were randomly selected and transferred into a plastic box containing a moist sponge. At the end of the pupal stage, the number of emerged adults was recorded three times a day. Ovarian maturation. Newly-emerged flies (age <4 h) (150 males and 150 females) were confined in a transparent meshed plastic cage. Adult flies had free access to a diet of sugar, enzymatic yeast hydrolysate and water. Ten females were dissected daily to check for the presence or Fig. 1. Influence of temperature on the developmental absence of mature eggs in their ovaries. rate (100/day) of the egg stage of Ceratitis capitata. Analysis. The lower development threshold temperature t (i.e. the temperature at which the stage and the ovarian maturation period, whereas development rate is zero) was then determined by few differences were found at the egg stage. extrapolation of the regression line back to the Minimum developmental threshold tempera- x-axis. The thermal constant K (i.e. the number tures (t) and thermal constants (K) for C. capitata, of day-degrees above the lower threshold re- C. rosa and C. catoirii are given in Table 1. C. rosa quired to complete development) was calculated and C. catoirii had lower minimal temperature from the regression equation using the relation- thresholds values than C. capitata, especially in ship y = K/(x – t) (Fletcher 1989). the case of C. rosa larvae. This probably explains All development tests for immature stages were the distribution of C. rosa on Réunion, where it replicated four times. Ovarian maturation of also occurs in the highlands up to 1500 m. How- females was determined using three replicates of ever, no ovarian maturation was observed for C. 10 females. Standard analysis of variance (ANOVA) rosa at 15°C (Table 2) although the temperature was used to analyse developmental time or threshold calculated for this stage is low. Larvae survival rate of the three species. Means were may be the cold-tolerant stage of the species compared by Student Newman-Keuls multiple during the winter period. range tests (P = 0.05) (Statistica 99, Statsoft). It is difficult to explain why C. catoirii is only present in low-altitude areas considering that it RESULTS AND DISCUSSION has rather low temperature thresholds. In addi- The linear model fitted well for the four stages tion, C. catoirii is more prevalent on the eastern and the three species in the range 15 to 30°C. The coast, the wettest region of the island. It is results for the egg stage of C. capitata are given speculated that high humidity is a favourable in Fig. 1. The species differed mainly at the larval factor for the development of C.catoirii in this area. Duyck et al.: Developmental biology of three fruit fly species on Réunion Island 69

Table 2. Mean duration of ovarian maturation period of Ceratitis capitata, C. rosa and C. catoirii at five temperatures.

15°C 20°C 25°C 30°C 35°C Species Mean ± S.D. Mean ± S.D. Mean ± S.D. Mean ± S.D. Mean ± S.D. (days) (days) (days) (days) (days)

C. capitata 20 ± 4.0 7 ± 0.6 b 5 ± 0.1 c 5 ± 0.6 c No maturation C. rosa No maturation 13 ± 2.3 a 8 ± 1.5 b 7 ± 1.0 b No maturation C. catoirii No maturation No maturation 14 ± 0.6 a 11 ± 1.0 a No maturation

Means in a column followed by a different letter are significantly different (P < 0.05).

The lower diversity and abundance of host fruits Finally, this study constitutes a first step before of C.catoirii on the western coast could also help to analysing more complex ecological relations such explain the distribution of the species. as interspecific competition. Releases of parasitoids for biocontrol or releases of sterile flies for eradication programmes require REFERENCES regular, large scale production of mass-reared BREVAULT, T. & QUILICI, S. 2000. Relationships between flies. Temperature plays a key role in the insect temperature, development and survival of different breeding process. Our results should contribute life stages of the tomato fruit fly, Neoceratitis cyanes- to the improvement of rearing methods for the cens. Entomologia Experimentalis et Applicata 94: 25–30. three species studied. A good compromise ETIENNE, J. 1973. Conditions artificielles nécessaires à between minimum developmental time and maxi- l’élevage massif de Ceratitis rosa (Diptera : Trypeti- mum survival rate would be to maintain eggs dae). Entomologia Experimentalis et Applicata 16: and larvae at 30°C for C.capitata and C.catoirii and 380–388. 25°C for C. rosa. A temperature of 25°C appears to ETIENNE, J. 1982. Etude systématique, faunistique et be the most suitable for pupal development of the écologique des Tephritides de La Réunion. Thèse three species. However fluctuating temperatures de l’École Pratique des Hautes Études, Paris. may sometimes accelerate rearing procedures; FLETCHER, B.S. 1989. Temperature-development rate relationships of the immature stages and adults of in particular a lowering of temperature at night tephritid fruit flies. In: Robinson, A.S. & Hooper, G. stimulates popping out of C. rosa larvae (Myburgh (Eds) Fruit Flies, their Biology, Natural Enemies and 1963; Etienne 1973). The present work also pro- Control. World Crop Pests. 273–289. Elsevier, Amster- vides information on the rearing of C. catoirii dam. whose thermal requirements were unknown. HANCOCK, D.L. 1989. Pest status. Southern Africa. In: These data combined with results of other Robinson, A.S. & Hooper, G. (Eds) Fruit Flies, their studies on trapping and population fluctuations Biology, Natural Enemies and Control. World Crop conducted on Réunion Island over recent years, Pests. 51–58. Elsevier, Amsterdam. MYBURGH, A.C. 1963. Diurnal rhythms in emer- should be useful in the construction of computer gence of mature larvae from fruit and eclosion of simulation models of fruit fly population dynamics adult Pterandrus rosa (Ksh.) and Ceratitis capitata that will enable better monitoring and manage- (Wied.). South African Journal of Agricultural Sciences ment of these important pests. 6: 41–46.