BIOLOGICAL AND MICROBIAL CONTROL Virulence of Metarhizium anisopliae (Deuteromycotina: Hyphomycetes) on Anastrepha ludens (Diptera: Tephritidae): Laboratory and Field Trials ROBERTO LEZAMA-GUTIE ´ RREZ, 1 AUGUSTA TRUJILLO-DE LA LUZ, 2 JAIME MOLINA-OCHOA, 1 OSCAR REBOLLEDO-DOMINGUEZ, 1 ALFONSO R. PESCADOR, 3 MARILU ´ LO ´ PEZ-EDWARDS, 1 AND MARTIN ALUJA 4 J. Econ. Entomol. 93(4): 1080Ð1084 (2000) ABSTRACT Twenty isolates of the fungus Metarhizium anisopliae (Metsch.) Sorkin (Ma) were evaluated to determine their virulence against last instar and adult emergence of Mexican fruit ßy, Anastrepha ludens (Loew). Larvae were exposed by immersion in a conidial suspension at a concentration of 10 8 UFC/ml under laboratory conditions. Larvae and pupae cumulative mortality rates ranged from 37.9 to 98.75%. Thirteen isolates caused mortality rates 83.7%, and their LT 50 values ranged from 1.8 to 6.2 d. The Ma2, Ma8, and Ma16 isolates were evaluated at seven different concentrations ranging from 10 1 to 10 7 UFC/ml, showing LC 50 values from 3.7 to 4.8  10 5 UFC/ml. In a Þeld-cage experiment, 200 ml of a conidial suspension of Ma2, at a concentration of 2.5  10 6 UFC/ml, was applied on 2,500 cm 2 soil surface (2  10 5 UFC/cm 2 ). The fungus reduced adult emergence, 22% fewer adults emerging in a sandy loam soil, and 43% fewer in loam soil, compared with the controls. M. anisopliae may offer a preferable alternative to chemicals as a biological control agent against A. ludens. KEY WORDS Metarhizium anisopliae, entomopathogenic fungus,Mexican fruit ßy, Anastrepha ludens, biological control FRUIT FLIES ARE among the most potentially damaging fruit pests worldwide. One of the most important spe- cies is the Mexican fruit ßy, Anastrepha ludens (Loew); it is a major pest of citrus, mango, guava, and other subtropical fruits (Aluja 1994). The Animal and Plant Health Inspection Service of the United States De- partment of Agriculture (USDA-APHIS) has estab- lished rigorous quarantine restrictions to control the movement of fresh fruits from tropical countries into the United States. Mango and citrus fruits from Mexico have exportation restrictions, because they are at- tacked by fruit ßies of the genus Anastrepha (Bustos et al. 1992). Their control has a long history in Mexico, the Þrst efforts having been documented in the late 1800s (Aluja 1994). Unitl now, within-Þeld control efforts have consisted almost exclusively of insecticide baits and sprays applications, massive release of sterile insects, parasitoids, and mechanical control (Aluja and Liedo 1986). Because ethylene dibromide was banned by the U.S. Environmental Protection Agency as a fumigant for treatment of fruits imported to the United States, the current concern is to Þnd econom- ically and environmentally sound alternatives for the control of fruit ßies. One such alternative currently considered is the use of biological control agents, including entomopathogenic microorganisms (Aluja 1994). The susceptibility of various species of fruit ßies to entomopathogenic nematodes has been reported by Lindegren et al. (1990) and Lezama-Gutie ´ rrez et al. (1996) and to the bacterium Bacillus thuringiensis (Berliner) (Robacker et al. 1996). Only a few fungi have been evaluated for the control of fruit ßies. The fungus Metarhizium anisopliae (Metsch.) Sorokin has been reported infecting adults of the Mediterranean fruit ßy, Ceratitis capitata (Wiedemann), under lab- oratory conditions (Garcia et al. 1984). This fungus has been used widely for biological control of agricultural pests and other soil inhabiting insects (Zimmermann 1993). Because the last instarts of fruit ßy emerge from dropped mature fruit, and pupate in the soil around the base of susceptible host plants, they could come into contact with M. anisopliae. This article reports the virulence of M. anisopliae isolates against A. ludens larvae in laboratory studies, and the effect of the most virulent isolate on the emergence of A. ludens adults when it is applied to the soil surface under Þeld con- ditions. 1 Facultad de Ciencias Biolo ´ gicas y Agropecuarias de la Universidad de Colima. Apartado Postal 36, C. P. 28100, Tecoma ´ n, Colima, Mexico. e-mail: rlezama@tecoman.ucol.mx 2 Secretaria de Agricultura, Ganaderõ ´a y Desarrollo Rural. Medellin No. 560, C. P. 28000, Colima, Colima, Mexico. 3 Centro Universitario de Investigacio ´ n y Desarrollo Universitario. Apartado Postal 36, C. P. 28100, Tecoma ´ n, Colima, Mexico. 4 Instituto de Ecologõ ´a, A. C., Apartado Postal 63, C. P. 91000, Xalapa, Veracruz, Mexico. 0022-0493/00/1080Ð1084$02.00/0  2000 Entomological Society of America Downloaded from https://academic.oup.com/jee/article/93/4/1080/2217225 by guest on 13 January 2022