REPRODUCTIVE PERFORMANCE OF THE MITE Brevipalpus phoenicis (GEIJSKES, 1939) ON CITRUS AND COFFEE, USING LIFE TABLE PARAMETERS

The flat-mite Brevipalpus phoenicis (Geijskes, 1939) (Acari: Tenuipalpidae) is considered important in citrus (Citrus spp.) and coffee plants (Coffea spp.) in Brazil, and is known as the leprosis and coffee ring spot mite, as being a vector of the Citrus Leprosis Rhabdovirus CitLV and Coffee Ring Spot Virus CoRSV. The objective of this work is to find out about the reproductive success of B. phoenicis on citric fruits and coffee leaves by fertility life table parameters and its biology. The experiments were carried out in laboratory conditions at 25 ± 2 °C, 70 ± 10% of relative humidity and 14 h of photophase. The lengths of embryonic and post-embryonic periods were different due to the host where the mite was reared. B. phoenicis showed better development and higher survival and fecundity in citric fruits than coffee leaves. The intrinsic rate of the population increase (r m ) was 0.128 and 0.090 females/female/day on citric fruits and coffee leaves, respectively. The citric fruits were more appropriate for the development of B. phoenicis than coffee leaves.

It is considered important in citrus and coffee plantations in Brazil, where it is known as the citrus leprosis mite and coffee ring spot mite for being a vector of the Citrus Leprosis Rhabdovirus -CitLV (Chiavegato et al., 1982;Gravena et al., 1994) and of the Coffee Ring Spot Virus -CoRSV (Chagas, 1973).The mites are found on leaves, branches and fruit of the citrus (Martinelli et al., 1976) and coffee plantations (Reis et al., 2000), usually in low population densities, but can cause damage due to virus transmission.The biological data of B. phoenicis have already been obtained in several hosts, such as papaya by Haramoto (1969); Indian tea by Oomen (1982) and Kennedy et al. (1996); Oroxylum indicum Vent.and Clerodendron siphonanthus R. Br. by Lal (1978) and in citrus, Citrus sinensis (L.) Osbeck, by Chiavegato (1986), demonstrating that the development and reproduction of the mite vary considerably in relation to the species of host it feeds on.In spite of all the study examples mentioned, there is no study that compares the reproductive performance of B phoenicis in different hosts using the fertility life table.In agreement with Kennedy et al. (1996) the economical importance of B. phoenicis is largely due to its high fertility and survival rate as well as reproductive intensity in the first days of oviposition, diapause absence, thelytokous parthenogenesis as main reproduction forms and polyphagia.The construction of the life table enables us to characterize demographic properties, such as the intrinsic rate of population increase, the net reproduction rate, the necessary time for the population to double, as well as the distribution of different ages of a population (Kennedy et al., 1996) enabling us to evaluate the biotic potential of a species under certain conditions.
Therefore, the objective of this work is to evaluate the reproductive performance of B. phoenicis in two of its main host plants in Brazil (citrus and coffee) parameters calculated from the fertility life table and biology.

MATERIAL AND METHODS
The biological studies of B. phoenicis in citric fruits (C.sinensis) and in coffee leaves (Coffea arabica L.) were accomplished simultaneously at the Laboratório de Acarologia do Centro de Pesquisa em Manejo Integrado de Pragas e Doenças de Plantas -EcoCentro, of the Empresa de Pesquisa Agropecuária de Minas Gerais -EPAMIG, in the Campus of the Universidade Federal de Lavras -UFLA, at 25 ± 2 °C, 70 ± 10% of relative humidity and 14 h of photophase.The experimental plot was randomly constituted from an orange or coffee leaf.The number of repetitions varied in relation to the availability of the mites in each phase of the development studied can be seen in Table 1.
Maintenance rearing in citrus and in coffee plants -Maintenance rearing of the mite in citrus was carried out using fruit from the "Valência" (C.sinensis) variety collected at an orchard where pesticides were not applied.The methodology used was similar to that used by Chiavegato (1986), where the citric fruit was made waterproof by using paraffin, independently separated in an area of 3 cm of diameter and surrounded by glue (Tanglefoot®) as an arena for rearing the mite.
Concerning the coffee, the rearing stock was carried out on leaves from the Catuaí Vermelho (C.arabica) variety collected from a plantation around 20 years old, which had not received pesticides.They were placed on a 2 cm thick sponge, constantly humidified with distilled water, which occupied the whole interior of a 15 cm diameter by 2 cm deep Petri dish without a cover.The leaves served as a food source and arena for rearing.Each leaf received a fine layer of hydrophilic cotton of approximately 2 cm wide overlapping the borders and in contact with the humidified sponge, with the purpose of maintaining the turgescence and to avoid the mites escaping (Reis et al., 1997).
Embryonic development -To collect the eggs and determine the incubation period, females of B. phoenicis were maintained in ten citric fruits and ten coffee leaves, as described in the maintenance rearing, for a period of four hours.The eggs were observed daily at 8 h a.m. and 4 h p.m. to determine the moment of the larva eclosion and the viability or percentage of eclosion.762 and 219 eggs on citrus and coffee were observed, respectively.
Post-embryonic development -At the end of the incubation period, newly hatched larva were individualized in citric fruit and coffee leaves, and observed daily at 8 h a.m. and 4 h p.m.The postembryonic development was studied in 35 citrus larvae and in 25 coffee larvae (repetitions), until reaching the adult phase.In each substratum, they were quantified, in days, the duration and survival of the egg phases, larva, protochrysalis, protonymph, deutochrysalis, deutonymph, teleiochrysalis and egg-adult periods of males and females.In the adult phases, the pre-oviposition, oviposition, postoviposition periods and longevity were observed.
Life history parameters -Parameters were obtained by survival data (l x ) in relation to age (x) and specific fertility (m x ) of 29 individualized females in citric fruits and 23 individualized females in coffee leaves (repetitions).Only females were used because B. phoenicis reproduces mainly by deuterotokous parthenogenesis, where nonfertilized eggs can produce either females or males.The experiments were evaluated daily at 5 h p.m. by counting the number of dead mites and oviposition until the death of all females.The sex ratio, that indicates the proportion of females, was calculated by the quotient between the number of females and the number of females added with the number of males.
Fertility life table -The fertility life table was made starting from the survival rate and specific fertility obtained from parameters of the life history and sex ratio (Birch, 1948;Dinh et al., 1988).Using the data from the life table, calculations were made for the net reproduction rate (R o ) or the number of times that the population increased in each generation (R o = Σ m x .lx ) and the intrinsic rate of increase (r m ) which expresses the number of females added to the population per female per day by the Lotka equation (Carey, 1993): Where T is the class age, l x is the proportion of live females (survival) beginning from the birth until the age x, and m x is the number of individuals produced by a female in the interval of x to x + 1. Estimations were also made for the finite reason of increase (λ), in other words, the number of times that the population grows a day (λ = e r m ), the average duration of a generation (T = ln R o / r m ) and the necessary time for the population to double (ln 2/ r m ), according to Reis & Alves (1997) and Reis et al. (1998).The times necessary to reach 50% mortality (TL50) and 100% mortality (TL100) were obtained by using the fertility life table.TL50 corresponded to the age x where the survival (l x ) presented a value close to 0.50 (Reis et al., 1998).

RESULTS AND DISCUSSION
Embryonic period -The shortest incubation period observed for B. phoenicis in citric fruits was of 6 days with 12.35% hatching and the longest was of 9 days with 0.13% hatching, with an average duration of 7.43 ± 0.54 days (Table 1).Most of the hatchings (51.26%) occurred 6.3 days after laying.On the other hand, when the mite was raised on coffee leaves the shortest embryonic period occurred at 8.7 days with 7.01% hatching and the longest at 13 days with 0.47% hatching with an average duration of 10.71 ± 0.83 days (Table 1).Most of the hatchings (52.34%) occurred at 9.7 days after laying.In this manner, B. phoenicis presented an incubation period significantly shorter in citrus than in coffee.The viability of the eggs calculated by the number of hatched larvae was of 98.82 in citrus and 97.72% in coffee.Chiavegato (1986) found an average period of incubation of 7.71 ± 0.48 days in citric fruit at 25 ± 1 °C for the same mite, a very close result of that also obtained in this work for citrus.Haramoto (1969) and Kennedy et al. (1996) had already observed average periods of incubation of 9.4 days in papaya at 25 °C, and 9.53 ± 1.71 days in Indian tea leaves at 26 °C.These results demonstrate that B. phoenicis presents a variation in the duration of the embryonic period due to the host in which the female develops.
Post-embryonic period -The duration of the immature phases was always significantly shorter in mites raised on citric fruit than in those raised on coffee leaves.The egg-adult period was also significantly shorter in citrus (17.27 ± 1.11 days) than in that of coffee (25.18 ± 1.58 days) (Table 1), which can be an indication that the citrus (in comparison with the two hosts) can be more appropriate for the development of the mite.The egg-adult period found by Chiavegato (1986) is close to that found in this work for the citrus.For the same mite, egg-adult periods observed by Haramoto (1969) in papaya fruits at 25 °C was of 29.3 days.In Indian tea at 19.1-23.4°C the eggadult period observed by Oomen (1982) was of 33.5 days.In O. indicum and C. siphonanthus at 26.6 °C, as mentioned by Lal (1978), that same period was of 20.7 and 20.2 days, respectively.The pre-oviposition and post-oviposition periods were significantly shorter in citrus than in coffee, while the inverse was observed for the oviposition period.B. phoenicis continued through oviposition for 34.90 ± 5.03 days in citric fruits and 22.00 ± 4.42 days in coffee leaves.The duration of the post-embryonic phases, as well as the preoviposition, oviposition and post-oviposition periods varied in agreement with the host in which the mite developed (Table 1).
Life history parameters -The values of the survival rate (l x ) and specific fertility (m x ) of B. phoenicis in citric fruits and coffee leaves are presented in Table 2.The survival rate (proportion of live females at age x) and the specific fertility (average number of descendants produced by female at age x) of the mites raised on citric fruit were larger than those of coffee leaves.B. phoenicis presented 1.09 ± 0.18 and 0.70 ± 0.22 eggs/female/ day on average in citrus and in coffee, respectively (Table 2).By only using unfertilized females, the effect of fecundation was not evaluated in the survival and oviposition of B. phoenicis.For another species, the phytophagous mite Oligonychus ilicis (McGregor, 1917) (Acari: Tetranychidae), Reis et al. (1997) found a higher survival and oviposition of females not fecundated in comparison with fecundated females.The higher oviposition of B. phoenicis in citrus rather than in coffee results in a larger population in that host which can be an explanation for the greater importance of the leprosis in citrus than of the ring spot in coffee.
The sex ratio was found to be the same as 1 in citrus (100% females) and 0.98 (98% females) in coffee.This high sex ratio was expected because B. phoenicis reproduces mainly by thelytokous parthenogenesis, in other words, non-fecundated females produce females identical to the progenitor (Haramoto, 1969;Helle et al., 1980), sexual repro-

Fig. 1 -
Fig.1-Evolution of the intrinsic rate of population increase (r m ) of Brevipalpus phoenicis in citric fruit and coffee leaves, at 25 ± 2 °C, 70 ± 10% of UR and 14 h of photophase.

TABLE 1 Duration, in days, of life cycle phases of Brevipalpus phoenicis rearing in citric fruit and coffee leaves, at 25 ± 2 °C, 70 ± 10% of relative humidity and 14 h of photophase.
Standard mean error (SE);3The averages of all analyzed parameters differed significantly among the utilized substrates (citrus and coffee) by the F test at 5% of significance.