Population Dynamics and Infestation Rate of Fruit Flies in Stone Fruits in São Paulo State, Brazil

Fruit fly species (Diptera: Tephritidae) are considered key pests in peach (Prunus persica L. Batsch) and plum (Prunus salicina Lindl.) crops in Brazil, causing both fruit losses and increased fruit costs due to greater use of spray insecticides. To measure the degree of infestation, for this study mature fruits were randomly collected over 2004 2006 period from a canopy of 34 varieties of peaches, nectarines and plums, as well as from ungrafted Mume and Okinawa rootstocks in the southwestern region of the São Paulo state, Brazil. Recovered fruit fly pupae were kept in a small cage until adult emergence. Except for “Harry Pickstone”, all other stone-fruit varieties were infested Original Research Article Raga et al.; ARRB, 14(6): 1-11, 2017; Article no.ARRB.34005 2 by Tephritidae. From 1,454 Tephritidae pupae, 1,310 adults emerged. We found 669 Ceratitis capitata (Wied.) (361 females and 308 males) and 641 Anastrepha fraterculus (Wied.) (297 females and 344 males). The three varieties of nectarine (Josefina, Rosalina and Rubro-sol) studied were highly susceptible to A. fraterculus, having average rates of infestation above 1.60 adult per fruit. Peaks of both fruit flies species occurred between october and december 2004.


INTRODUCTION
Global production of fruit has experienced a remarkable increase, with Latin America and the Caribbean accounting for over 13% of the growth. Output has been rising at an annual rate of approximately 3% over the last decade [1]. In 2011, almost 640 million tons of fruit, and more than 1 billion tons of vegetables, were produced in the world. Brazil is the largest fruit producer in Latin America, and the third-leading supplier in the world [1].
Although most commercial citrus production in Brazil (563,000 ha) is concentrated in São Paulo, there are locations where winter temperatures range from 0-150 cold hours [2], providing favorable conditions for stone-fruit crops.
In 2014, Brazil produced 211,109 tons of peaches and nectarines [3]. The economic potential of peach and nectarine crops in the state of São Paulo stems from the competitive advantage its earlier harvesting period, affords in relation compared not only to the main Brazilian producing regions, but also most of rival countries located in the Southern Hemisphere, such as Chile, Argentina, Uruguay, and South Africa [4]. In 2014, the state of São Paulo had approximately 495,000 fruit-producing peach trees [5]. Species of fruit flies (Diptera: Tephritidae) are insect pests that cause economic losses in stone-fruit production in Brazil.
In São Paulo state, located in the southeastern region, the medfly Ceratitis capitata (Wied.) was detected at the beginning of the 20 th century, and coexists with at least 35 Anastrepha species. Ceratitis capitata and A. fraterculus (Wied.) are particularly noticeable due to the large number of reported hosts in São Paulo, and infest fruits from over 15 plant families [6,7,8]. The South American fruit fly Anastrepha fraterculus is especially abundant in species of Citrus, Rosaceae and Myrtaceae from the southern and southeastern Brazilian regions [6,9].
Among the tephritids reported for the state of São Paulo, A. fraterculus, C. capitata, A. obliqua (Macquart), A. sororcula Zucchi, and A. turpiniae Stone may infest peaches [6, 10,11,12], while the incidence of A. fraterculus and C. capitata is recorded in plums [6,11]. To avoid or prevent crop losses, insecticides are used as cover sprays to control fruit flies in peach and plum crops in Brazil once the fructification period begins.
A accurately determining the status of a particular plant species as the host of a given fruit fly has become critical because of intensive international trade and the expansion of fruitgrowing regions in many parts of the world [13]. Most of the pome fruits and stone-fruit cultivars grown commonly today, were chosen for their quality characteristics. Until recently, resistance to insect pests and diseases has generally not been the focus for selection [14].
Research on the incidence and the degree of infestation by fruit flies in different genetic materials of Rosaceae is rare in Brazil. By assessing population dynamics and undertaken a comparative evaluation of natural infestation by Tephritidae, this study aims to further the advancement of Integrated Pest Management and add the genetic improvement of stone-fruits (Rosaceae). The experimental area measured 2,415 m 2 , and peach, plum, and nectarine plants on an Okinawa rootstock, as well as ungrafted Okinawa and Mume rootstocks of were evaluated. The materials were eleven years old. Each material consisted of three trees. The spacing between trees was 5 m x 3 m. During the collections, there were no applications of insecticides.

Population Dynamics of Fruit Flies
The population dynamics of adults were assessed, from January 9, 2004 to March 27, 2006, using 10 yellow-based, Mc Phail traps baited with 400 ml of hydrolyzed protein solution (Bio Anastrepha) at 5% v/v. Traps were installed at an approximate height of 1.60 m from the canopy in a shaded area, and distanced at least 20 m apart.
Captured insects were collected, and the attractant renewed weekly. The tephritids collected were separated from the solution, transferred to labelled glass vials, containing 70% alcohol, and delivered to the Economic Entomology Laboratory of the Biological Institute in Campinas (SP) for screening, subsequent sexing, counting, and identification. Any fluctuation in population was demonstrated by the fly/trap/day (FTD) index. The fruit samples of each cultivar were transferred to the Economic Entomology Laboratory of the Biological Institute in Campinas (SP), where they were counted and weighed. The samples were individualized in 250 ml volume, lined with a bottom substrate layer made up of an equivalent mixture of sand and vermiculite. The containers were capped with voile bound with elastic. Approximately 20 days after collection, when the egg-larval period is completed, the fruits were removed from the containers, and sieved to recover the pupae. These pupae were kept, in their respective containers, in an acclimatized room (25 ± 2°C and 70 ± 10% relative humidity) for an additional period of 20 days to allow the emergence of adults. The emerged tephritids were counted and transferred to 50 ml glass containers containing 70% ethanol and top with rubber caps, for later sexing and identification.

Diversity of Fruit Flies Species
The identification of the Anastrepha specimens was based on the aculeus of females [15][16][17]. Ceratitis individuals were counted and sexed, because only C. capitata has been reported in Brazil [6].

Statistical Analysis
The population fluctuation results for Tephritidae adults were correlated with two climatic variables (temperature and rainfall volume), using the Statistical Analysis System (SAS) program, with significance level for Pearson's correlation coefficient measuring 5%. Rainfall and temperature data were obtained from a local meteorological station located approximately 250 m from the experimental area.
The fauna analysis was based on the Simpson index, frequency, dominance, constancy (Shanon-Wiener index), equitability (modified Hill index), and richness (Margalef index) of species obtained from fruits, by summation of the two crop seasons [18].  (Fig. 2).

Population Dynamics of Fruit Fly Species
Ceratitis capitata and A. fraterculus are polyphagous species, and the population peaks of these species are influenced by the availability of several host fruits [8,12] under favorable environmental conditions. In São Paulo state, the early emigrant populations of C. capitata in stone fruit orchards probably originate from citrus orchards, coffee plantations, or both [9,21], because the fructification of these stone fruits begins approximately two months after the coffee or mid-season citrus harvest. The medfly has many host plants also listed for A. fraterculus [6, 13,22], a wide geographic distribution in Brazil, and a dominance in urban and peri-urban environments.
If two or more species coexist, competition for the host may occur [23]. The population peaks of C. capitata and A. fraterculus were very similar in stone fruits, proving that both species coexist and exploit the same resources. The population peak of fruit flies was obtained on 01/ 16 [27]. The low adult capture values of other species, as recorded in this study, suggests that the specimens captured migrated from other hosts, seeking shelter, reproduction, or food. The number of flies captured in traps suggests that fruit fly populations were directly affected by host-fruit availability [28].
The reduced value of the Shannon index (0.75) supported the low diversity observed in the orchard, was identical to that obtained in Piracicaba (SP) [29], and was greatly inferior to the value obtained for a mixed orchard in the southern Bahia state (1.35) [27]. Genetically close plants probably do not favor a greater diversity of Tephritidae species. The Hill modified index measures the equitability, or the way abundance is distributed in the community of species [29]. In this study, the value of this index was 0.39 and together with the Margalef index (0.80), it confirmed the dominance of A. fraterculus and C. capitata, at the expense of other species.
A dominance of C. capitata and A. fraterculus in guava and sweet orange in commercial orchards was observed in the northwestern region of the state of Rio de Janeiro [30]. In southern Brazil, where average winter temperatures are lower, there is a higher incidence of A. fraterculus during the fruiting period of peaches (December and January), with accidental collections of C. capitata [31,32].
In eastern and western areas of the state of São Paulo, there are dominances of A. fraterculus [12] and C. capitata [10], respectively, in peach trees. It is likely that during the fruiting period in the Capão Bonito region, the two species can satisfactorily explore the local environment and meet their foraging requirements. Furthermore, the São Paulo southwestern region may be a transition region, in which there is no predominance of a single species, due to competitive ability in the agroecosystem.
There were infestations by both Tephritidae species in fruits from trees grafted onto "Okinawa" and mume rootstocks, but with a dominance of medflies ( Table 1). The resistance mechanisms in Tephritidae are dynamic and may be species-specific [33]. The "Fla 86-2" and "Fla 87-7" varieties had the highest average rates of infestation among plum trees (1.74 and 1.92 adult per fruit, respectively), coming close to the rates observed for nectarines.  [34].
In the municipality of Monte Alegre do Sul, in the eastern region of the São Paulo state, infestations by A. fraterculus, C. capitata, and A. obliqua were observed in peaches, while only the first two species were recovered in loquats [12]. In the municipality of Presidente Prudente, located in the far-western region of the São Paulo state, there is a predominance of medflies in peaches as related to Anastrepha spp. [10].
In eastern São Paulo, the infestation by C. capitata in peaches occurs in August and September, with medflies practically absent from peach and loquat orchards in January-July, a period when A. fraterculus is dominant [10]. This explains the higher incidence of medflies in the far-western region of the São Paulo state, where fruiting occurs in August and September, when orchards are susceptible to immigrant populations of C. capitata from the coffee postharvest period [9,21].
The fructification of peaches, plums, and nectarines occurs in Capão Bonito in an intermediary period, between those verified for the eastern and the extreme western regions of the São Paulo state, with a much greater balance between infestation rates by both Tephritidae species. Equivalent infestations by A. fraterculus and C. capitata in peaches were also observed in the Tucumán region (northern Argentina) [13].
Both fruit fly species presented a relative abundance in various parts of Argentina, exploring the same host and coexisting with similar ecological requirements [34]. In Pelotas (RS), a natural infestation by A. fraterculus was detected in plums of "Amarelinha", "Pluma", "Santa Rosa", "Reubennel" and "Wade" cultivars, with damage in fruits measuring approximately 2.0-3.0 cm in diameter [35].
In the municipality of Presidente Prudente (SP), there was no statistical difference in the fruit fly infestation of different cultivars grafted on "Okinawa" [10], when "Aurora-2" reached 23% of fruit infestation by C. capitata in 2006. In the present study, fruit flies infested approximately 54% of "Aurora-2" fruits, with a dominance of A. fraterculus.
Ample evidence revealed that not all cultivars within a particular fruit species were equally susceptible to infestation. Such information needs to be considered when determining the status of the host plant, and calculating the risk of introduction or spread of flies by infested fruits [33].