International Journal of Entomology Research 23 International Journal of Entomology Research ISSN: 2455-4758 Impact Factor: RJIF 5.24 www.entomologyjournals.com Volume 2; Issue 6; November 2017; Page No. 23-26 Pathogenicity of Beauveria bassiana against cucurbit fruit fly Dacus ciliates (loew) Diptera: Tephritidea 1 Mutadar Alaa Faleh, 2 Bassim Shehab Hamad, 3 Ammar Ahmed Sultan 1 M.SC. Biology, University of Diyala, College of Education for Pure Science, Baqubah, Iraq 2 Ph.D. Biology, Ministry of Science and Technology, Directorate of Agric. Res. / IPM Center, Iraq 3 Ph.D. Biology, University of Diyala, College of Education for Pure Science, Baqubah, Iraq Abstract The current study was conducted to evaluate the efficiency of three local isolates of Beauveria bassiana on two stages (larvae and adults) of cucurbit fruit fly Dacus cilliatus under laboratory conditions. The results showed that both stages were sensitive to the concentrations of 10 5 , 10 7 and 10 9 spores / ml. Depending on the LC50 values the highest efficiency on females was achieved by the isolate Bb100, it was 1 × 10 2 spores\ml. followed by Bb 17 isolate with the median lethal concentration of 1.1 × 10 5 spores\ml. The most severe isolates was Bb 100 depending on LT50 that was 4.15 days followed by Bb47 (4.5 days). According to LC50 values, Bb100 isolate was the most severe on males, the LC50 value was 8.3 x 10 3 spores\ml. and then Bb 17 (2.7 x 10 5 spores\ml.) and BE47 (5 × 10 6 spores\ml.). The results of median lethal time, which expresses on virulence, showed superior of Bb100 with LT50 2.5 days, then the isolate of BE47 (5.5 days) and Bb17 (9 days) at concentration of 10 9 spores / ml. Females were greater sensitivity than males when exposed to the suspension of all isolates. The effect of B. bassiana isolates on the cucurbits fruit fly larvae was measured depending on the adult’s emergence rates. The reduction rate of adults emergence was increased with increasing of concentration, the highest was at concentration of 10 9 spores\ml. (75%) for the isolate Bb 100 that significantly differed from other isolates, in both of them the reduction rate reached to 66%. Keywords: beauveria bassiana, dacus cilliatus Introduction Cucurbits crops (family: Cucurbitaceae) are a major horticultural crops cultivated for fruits, that characterized as high nutritional value and economic importance. They are exposed to a wide variety of insect pests, one of the most serious is the cucurbit fruit fly, Dacus ciliatus Loew (Diptera: Tephritidae) (White, and Elson-Harris, (1994 [17] ; Hancock, 2012) [9] . Its economic importance refer to the direct damage caused by females that oviposit into the host fruit and larvae feeding on the fruit flesh. In addition to direct losses, severe quarantine policies are imposed by importing countries to avoid importation and establishment of exotic pests. Because of the environmental impact of chemical pesticides and by the nature feed of their larvae inside the fruit, the chemical pesticides was ineffective strategy to control this pest, so it was recommended to find out safer alternative control strategies such as use of microbial control agents. Fungal agents belong to the most promising group of biological control agents against insect pests. Beauveria bassiana and Metarhizium anisopliae are two of the most important entomopathogenic fungi currently used against a wide range of arthropod, mainly insect pests, and the most common species developed as mycopesticides (Butt et al. 2001; Zimmerman 2007a, b) [2, 19, 20] . Different strains of B. bassiana or M. anisopliae cause different rate of mortality in their pest, due to genetic variability among their isolates (De La Rosa et al., 2002; Garcia et al., 1984). The objective of this study was to evaluate the pathogenicity of some isolates of B. bassiana and the mortality response of D.ciliatus under laboratory conditions. Materials and methods Insect rearing The infected fruits with eggs of cucurbits fly D. ciliatus were placed in cages of Plexiglas (40×40×40 cm) and were reared in the laboratory under optimal conditions (temperature 25–29 C; relative humidity 75–85%; photoperiod 16:8 h L: D) the larvae feed after eggs hatching on the fruit pulp, then leave the fruit after complete their growth and go down to the ground corn for pupate. Pupae were collected in Glass jar (14 cm high and 9 cm diameter), covered with cloth, and placed in incubators under similar conditions of rearing room, except it is without lighting. all emerging adult were transferred to mating cages (20× 20×20 cm) equipped with yeast solution as a source of protein for females and to improve the activity mating of males, and sugar solution 5% besides dry sugar as well as pieces of cotton moistened with water in a small Petri dish (Keiser & Schneider, 1969, Keiser, et al. 1972 and Drew, 1987). Mating cages were provided with fruits of ground as a natural medium to lay eggs, placed under the conditions of rearing room, these fruits have been replaced frequently. Fungal spore suspension preparation Three isolates of Beauveria bassiana (Bb100, Bb47 and Bb17) were grown on 9 cm Petri dishes containing Potato dextrose Agar PDA (39 g l -1 ) and incubation at 25 o c in darkness until