Larval Parasitoids Associated to Anastrepha distincta (Diptera: Tephritidae) in Two Host Fruits at the Soconusco Region, Chiapas, Mexico

Abstract

Anastrepha distincta Greene (Diptera: Te phritidae) is considered a pest of secondary im portance in Mexico because it is only associated with non-commercial fruits in the Inga genus (Fa baceae) (Norrbom & Kim 1988; Malo et al. 1987; Celedonio-Hurtado et al. 1995). However, there are reports of A. distincta infesting economically important fruits such as oranges (Citrus sinensis L.) and mangoes (Mangifera indica L.) (Norrbom & Kim 1988). During the last few years biological control of fruit flies has emerged as an alternative to syn thetic insecticides (Ovruski et al. 2000). There fore, it is important to determine the potential of parasitoids in regulating populations of various species of fruit flies under field conditions (Figueroa 1998; Ovruski et al. 2000; Montoya et al. 2000). The first step in developing a biological control program is an inventory of native parasi toids. Practical issues, such as which species are most suitable for mass rearing, might eventually be taken into account (Ovruski et al. 2000; Mon toya & Liedo 2000). Native host plants in rainforest areas provide an important reservoir of native and introduced Anastrepha parasitoids (L?pez et al. 1999; Aluja et al. 2003). Studies carried out in neotropical re gions indicate that populations of fruit flies such as A. ludens (Loew),A. obliqua (Macquart), A. ser pentina (Wiedemann), A. striata Schiner, A. fraterculus (Wiedemann), A. leptozona Hendel, and Toxotrypana curvicauda (Gerstaecker), are frequently associated with Diachasmimorpha longicaudata Ashmead, Doryctobracon areolatus Viereck, and D. craw fordi parasitoids (Aluja et al. 1990; Eskafi 1990; Figueroa 1998). Inga spp. are native species of tropical Amer ica and are widely distributed (Sousa 1993). Usu ally, these tress are used to provide shade for cof fee plants (Coffea arabica L.). They are also found naturally in the subdecidous forest, disturbed ar eas, and gardens (Miranda 1998). There are no reports of parasitoids attacking A. distincta under field conditions. The goal of this study was to identify the parasitoid species asso ciated with A. distincta infesting two natural hosts; Cuajinicuil (Inga spuria H. et B.), and Caspirol (7. laurina Wild), in the Soconusco re gion, in Chiapas, Mexico. The fruits of 7. spuria are lengthener (~15 cm), flattener, green colored, and become greenish-yellow when they mature. In the case of/, laurina fruits are shorter (~10 cm), bulkier and stay green, even when ripe. Inga spuria has two fruiting seasons per year; the first from Jan to Mar and the second from Aug to Sep Inga laurina has only one fruiting season per year; from Feb to Apr (Miranda 1998). The study site is at an altitude between 670 and 960 m above sea level, and geographical coor dinates are 15?02'irN latitude, and 92?05'64W longitude. The area's climate is defined as Af (tropical wet) with a mean annual temperature of 25.4?C, and 4,720 mm rainfall. The rainy season is rom May to Oct and the dry season lasts 5-6 months, from Nov to Apr (Garcia 2004). Anas trepha distincta larvae were obtained from in fested fruits that had fallen to the ground. The col lected fruits were transported to the laboratory of El Colegio de la Frontera Sur (ECOSUR) in Tapa chula, Chiapas. They were weighed, counted, and placed in plastic trays where they remained for 5 or 6 d until the larvae reached maturity (third in star), and began leaving the fruits. Subsequently, the fruits were dissected and the remaining third instar larvae were extracted and counted. All lar vae were placed in plastic containers (26 x 12 x 9 cm) with humid vermiculite in order to promote pupation. We found few younger larvae (234 in to tal in the 12 samples of the 2 host fruits), and they were separated from third instar larvae. Pupae remained in the containers for 13 d and they were sieved from the medium (Mesh 18 sieve), placed in containers, and covered with fine mesh until fruit fly and parasitoid adults eclosed. Fruit fly adults were identified with the taxonomic key by Hern?ndez-Ortiz (1992). Parasitoids were sepa rated by sex, counted, and placed in vials contain ing 70% alcohol. Species were identified by de scriptions in Wharton & Gilstrap (1983), Wharton & Marsh (1978), and Ovruski et al. (1996). Twelve samples of fruits were taken from each plant; 37.5 kg of /. spuria, and 36.9 kg of I. lau rina, which yielded 3,375 and 4,386 larvae, re pectively (Table 1). However, parasitoids emerged only from 3 samples from each host. In the case oil. spuria 3 species of parasitoids (Dia chasmimorpha longicaudata, D. tryoni, and Do ryctobracon crawfordi) were obtained. All 3 spe cies of parasitoids were found from a 9.1 kg sam ple oil. spuria fruits with an infestation rate of