versión impresa ISSN 1519-566X
Neotrop. Entomol. v.35 n.1 Londrina ene./feb. 2006
Susceptibility of guava genotypes to natural infestation by Anastrepha spp. (Diptera: Tephritidae) in the municipality of Monte Alegre do Sul, state of São Paulo, Brazil
Susceptibilidade de genótipos de goiaba à infestação natural por Anastrepha spp. (Diptera: Tephritidae) no município de Monte Alegre do Sul, SP
Adalton RagaI; Miguel F. de Souza FilhoI; Daniela A.O. PrestesI; Joaquim A. de Azevedo FilhoII; Mário E. SatoI
IInstituto Biológico, C. postal 70, 13001-970, Campinas, SP
IIAgência Paulista de Tecnologia dos Agronegócios (APTA), Rodovia Municipal Monte Alegre - Pinhalzinho, km 3 13910-000, Monte Alegre do Sul, SP
The infesting species and their infestation indices of fruit flies were determined for eleven guava genotypes (Psidium guajava L.). From March to April 2000, ten mature fruits of each genotype were harvested at weekly intervals from insecticide unsprayed trees located in the municipality of Monte Alegre do Sul, SP, Brazil. Fruits were brought to the laboratory, weighed and placed in individual plastic cups containing sand at the bottom to obtain the tephritid pupae. About 95% of guavas produced fruit fly puparia. Of the 682 Anastrepha females recovered, four species were identified: A. fraterculus (Wied.) (86.5%), A. obliqua (Macquart) (10.8%), A. bistrigata Bezzi (1.8%) and A. sororcula Zucchi (0.9%). Three species of parasitoids Braconidae (Opiinae) were recovered: Doryctobracon areolatus (Szépligeti), Doryctobracon brasiliensis (Szépligeti) and Utetes anastrephae (Viereck). The genotypes differ in level of infestation depend on the collecting time. The genotypes 'L2P4 Vermelha', 'Ruby Suppreme' and 'Webber Suppreme' showed the lowest susceptibility to tephritids in terms of puparia per fruit. The variability of infestation among the guava genotypes and the reasons for increasing fruit fly infestations along the time were discussed.
Key words: Insecta, fruit fly, Psidium guajava, Myrtaceae, infestation index
As espécies infestantes de moscas-das-frutas e seus índices de infestação foram determinados para onze genótipos de goiaba (Psidium guajava L.). De março a abril de 2000, dez frutos maduros de cada genótipo foram coletados em intervalos semanais, de plantas não pulverizadas com inseticidas, instaladas no município de Monte Alegre do Sul, SP. Os frutos foram trazidos para o laboratório, pesados e colocados em copos plásticos contendo areia para obtenção de pupas de tefritídeos. De 95% das goiabas coletadas foram obtidos pupários de moscas-das-frutas. Das 682 fêmeas de Anastrepha recuperadas, quatro espécies foram identificadas: A. fraterculus (Wied.) (86,5%), A. obliqua (Macquart) (10,8%), A. bistrigata Bezzi (1,8%) e A. sororcula Zucchi (0,9%). Três espécies de parasitóides Braconidae (Opiinae) foram recuperadas: Doryctobracon areolatus (Szépligeti), Doryctobracon brasiliensis (Szépligeti) e Utetes anastrephae (Viereck). Os genótipos diferiram quanto aos níveis de infestação dependendo da época da coleta. Os genótipos 'L2P4 Vermelha', 'Ruby Suppreme' e 'Webber Suppreme' mostraram menor susceptibilidade em termos de produção de pupários por fruto. A variabilidade de infestação entre os genótipos de goiaba e as razões do aumento no nível de infestação ao longo do tempo são discutidas.
Palavras-chave: Insecta, mosca-das-frutas, Psidium guajava, Myrtaceae, índice de infestação
Guava, Psidium guajava L. (Myrtaceae), is native to the American tropics and today is found in all subtropical and tropical regions (Kwee & Chong 1990, Gould & Raga 2002). The largest production in the world is registered in Brazil, where guavas are grown in commercial areas or as backyard fruits. In 2002, guava production in Brazil was estimated at 389.162 tons grown on 18,039 ha. About 37% of the commercial guava yield is concentrated in the State of São Paulo (Southeastern region) on 5,201 ha (Agrianual 2004).
Wherever guavas are grown commercially, fruit flies (Diptera: Tephritidae) are the key pests, including some species of the quarantine importance (Gould & Raga 2002). In Brazil, the medfly - Ceratitis capitata (Wied.) - and eleven Anastrepha species have been reported in guavas (Zucchi 2000a, 2001).
In four municipalities of São Paulo State, Bressan & Teles (1991) registered from guavas Anastrepha obliqua (Macquart), A. sororcula Zucchi, A. bistrigata Bezzi and A. zenildae Zucchi. The authors obtained 4.4 to 1082.7 puparia/kg of guava. Canal et al. (1998a) recovered A. zenildae and A. sororcula in guavas from north of the State of Minas Gerais (dry area), with a maximum of 116 larva/kg of fruits.
The host resistance to tephritids is an under-exploited control strategy, although review of literature yields numerous examples of fruits that are resistant to fruit flies, such as citrus, apples, avocados, mangoes, peaches and carambolas (Greany 1989, Branco et al. 2000). However, there are few studies concerned about plant resistance against Anastrepha species in guavas (Gould & Raga 2002).
To prevent fruit fly infestation in guavas, Brazilian growers adopted cover sprays for killing adults or wrapping of fruits (paper bag). New strategies are demanded by the IPM program to guarantee safety to growers and consumers. In this context, the objective of the present study was to evaluate the susceptibility of guava genotypes to the attack of the Anastrepha fruit flies under natural field infestation.
Material and Methods
Eleven guava genotypes were selected from a germplasm of 54 guava genotypes (408 trees, nine years old) belonging to APTA Regional Agricultural Station, in the municipality of Monte Alegre do Sul (22º41'S; 46º41'W; 748m), State of São Paulo, Brazil.
Choice of genotypes was based on former studies of yield (Santos et al. 1998) and physico-chemical parameters (Nascimento et al. 1991). The guava genotypes evaluated were 'Shimoda Vermelha', 'Monte Alto Vermelha', 'Webber Suppreme', 'Indiana Vermelha', 'Ruby Suppreme', 'Torrão de Ouro', 'Campos', 'Ogawa 3 Vermelha', 'Monte Alto Comum 1', 'Ogawa x Kumagai' and 'L2P4 Vermelha'. The grove was set at a 2.5 x 4.0 m space planting without irrigation system. Trees with 3.0 - 3.5 m high were kept free from pruning and insecticide treatments during fructification. During the fruit collection, the average temperature ranged from 21.5º to 22.7º C, with a rainfall of 219 mm.
Ten mature fruits of each genotype were picked from the canopy at a height of 1.3 to 2.0 m, on the following dates: March 16, 24 and 31, and April 06, 2000, totalizing four evaluation times. The fruits were brought to the laboratory, weighed and placed into individual plastic cups (460 cc) containing dry sand at the bottom (230 g) and covered by voile. Recovered puparia were counted and individually transferred to similar recipients as described above for guavas. Puparia were kept at about 25ºC and 70% of RH for 25 days, thus allowing for maximum emergence rate. A mixture of sugar and yeast extract (3:1) and water was used as food for adult flies. The infestation indices were estimated by means of the total number of puparia. Pupal viability was calculated based on the percentage of puparia that resulted in fly emergence. Identification of Anastrepha specimens were based on Zucchi (2000b). Braconidae wasps were identified according to Canal & Zucchi (2000).
Weight of fruits and infestation indices were transformed into log (x + 1) before the analyses of variance (ANOVA), and means were separated by Tukey's test (P < 0.05). Untransformed means are shown in Tables 1 and 2. The relationship between the weight of fruits and the number of puparia for each genotype was examined with bivariate correlation analysis (Ayres & Ayres 2003).
Results and Discussion
Fruit fly puparia were recovered from 95% of guava fruits. On the first evaluation (March 16, 2000) and the third evaluation (March 31, 2000), 'L2P4' was the genotype with the lowest infestation index of fruit flies, with means of 2.0 and 5.0 puparia/fruit, respectively (Table 1), and no significant differences were detected among the remaining genotypes. 'Indiana Vermelha' showed the highest infestation indices during the experiment, achieving 49 puparia from one fruit.
Infestation indices of the genotypes did not differ statistically on the second evaluation (March 24, 2000). On the last evaluation (April 06, 2000), the number of puparia/fruit in 'Webber Suppreme' and 'Ruby Suppreme' was significantly lower than in 'Indiana Vermelha', 'Ogawa 3 Vermelha', 'Monte Alto Comum 1', 'Ogawa x Kumagai', and 'Campos', and the remainder being similar among themselves (Table 1). The infestation indices by fruit flies increased in some genotypes during the collections, mainly for 'L2P4 Vermelha', whose mean infestation index increased eight times in comparison to the first evaluation (Table 1), probably due to the very ripe stage of its fruits. In general, senescent fruits are markedly more susceptible to attack by fruit flies than early season fruits (Greany 1989).
On the last evaluation, the infestations of the 'Ruby Suppreme' and 'Webber Suppreme' were lower than seven puparia/guava (Table 1). Suplicy Filho et al. (1984) performed a study to define the chemical and physical bases for differential resistance among guava cultivars and low pH appears to have an important effect on guava susceptibility to fruit flies. These authors found that the cultivar 'Australiana' (pH of 3.5 - 4.1) was less susceptible than 'Azeda' (pH of 3.1 4.0) based on the number of fruits infested by Anastrepha spp. No attempt was made to investigate this internal property of the fruits among the genotypes evaluated. Nascimento et al. (1991) evaluated twenty two cultivars in the same experimental area of the present study, and 'Rubby Suppreme' showed low means of total and titrable acidity (0.19 - 0.45) and pH of 4.0 - 4.6.
Suplicy Filho et al. (1984) also found that Brix and humidity of fruits have little effect on guava susceptibility, and there was no effect of weight of fruits. Results of overall weight of fruits for each guava genotype and their overall infestation indices are summarized in Table 2. The fruits of the genotypes 'Shimoda Vermelha', 'Ogawa 3 Vermelha', 'Indiana Vermelha', 'Ruby Suppreme', and 'Monte Alto Comum1' had significantly greater mean values (over than 100 g). 'L2P4' presented the lowest mean weight (38.7 g), followed by 'Torrão de Ouro' and 'Campos' whose mean weights were lower than 70 g. The overall infestation indices did not differ among the genotypes, ranging from 63.8 to 159.7 puparia/kg of fruit. No significant correlation (P > 0.05) was detected between the weight of fruits and the number of puparia for any evaluated genotype. Significant correlation (F = 5.02, degree of freedom = 1, P = 0.025, R2 = 0.44) between these parameters were detected only for global analysis including the eleven studied genotypes. No statistical differences were detected among the genotypes in terms of pupal viability (Table 2), whose means after four collections ranged from 25.8 to 50.9. In the north of Minas Gerais State, the tephritid pupal viability collected from guava under natural field infestation ranged from 2.8% to 100% depending on the fruit fly species (Canal et al. 1998a).
A total of 1,429 adults (52.3% males and 47.7% females) of Anastrepha emerged during the experiment (Table 3). More than 30% of the flies were recovered from 'Ogawa 3 Vermelha' and 'Indiana Vermelha'. Although C. capitata attacks guava (Zucchi 2001), adults of this species were not recovered during the evaluations. Probably this was due to the low population densities of this species at the evaluation times, in which its population was equal or lower than 0.03 fly/trap/day using McPhail traps with hydrolyzed protein installed in the same experimental station.
From 682 Anastrepha females recovered (Table 3), four species were identified: A. fraterculus (Wied.) (86.5%), A. obliqua Macquart (10.8%), A. bistrigata Bezzi (1.8%) and A. sororcula Zucchi (0.9%). A. fraterculus emerged from all genotypes and A. obliqua was not detected only in 'Ruby Suppreme'.
Similar results were found by Aguiar-Menezes & Menezes (2002) who recovered more than 50% of the adult fruit flies belonged to A. fraterculus, followed by A. sororcula (38%) and A. obliqua (7%) from guavas in the municipality of Itaguaí, State of Rio de Janeiro. In the north of Minas Gerais, Anastrepha zenildae Zucchi is dominant in guavas, with high pupal viability (72.4% to 100%) (Canal et al. 1998a,b; Corsato 2004), whereas in the Brazilian Amazon and Venezuela, that status is represented by A. striata (Silva & Ronchi-Teles 2000, Katiyar et al. 2000).
In the present study, the parasitism of tephritid larva also occurred, but only 21 Hymenoptera parasitoids emerged during the experiment. All belonged to Braconidae (Opiinae): Doryctobracon areolatus (Szépligeti) (19 specimens), Doryctobracon brasiliensis (Szépligeti) and Utetes anastrephae (Viereck). These results agree with Leonel Jr. et al. (1996) who mentioned that 90.4% of the braconids collected in guavas from the central region of São Paulo belonged to D. areolatus. Braconids recovered from guavas by Aguiar-Menezes & Menezes (2002), represented 73.6% of all parasitoids, from which the mean percent parasitism of D. areolatus ranged from 3.9 to 6.4%.
Results of this study demonstrate that all guava genotypes tested under natural infestation in the municipality of Monte Alegre do Sul, SP, are infested by Anastrepha. However, in addition to their advantages in commercial fruit size, 'Ruby Suppreme' and 'Webber Suppreme' showed to be promising genotypes in terms of low susceptibility to fruit flies and may contribute to the IPM programs against tephritid pests.
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Received 28/XII/04. Accepted 22/VIII/05.