Efficacy of Beauveria bassiana and Metarhizium anisopliae (Ascomycota: Hypocreales) against Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae) under controlled and open-field conditions on bitter gourd

Background Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae) is the most destructive pest of bitter gourd. Conventionally, it is controlled by chemical insecticides despite their hazardous impacts. Entomopathogenic fungi are considered as eco-friendly and safer alternative of chemical. This study aimed to evaluate the efficacy of Beauveria bassiana and Metarhizium anisopliae against B. cucurbitae on bitter gourd. Results The study revealed that B. bassiana and M. anisopliae were efficient against B. cucurbitae in controlled as well as field conditions. Both mode of application (i.e., contact and oral) were found to be effective; however, high efficacies of them were observed through contact application (73.43 and 59.72%), respectively. Pathogenicity of both fungi increased with increase in concentration and time intervals. Under field conditions, significantly low fruit infestations and significantly a high population reduction of B. cucurbitae were observed at 30 DAT when both fungi were applied with 108 CFU/ml concentrations. Conclusions Beauveria bassiana and M. anisopliae had the potential to be used against B. cucurbitae; however, the former showed high efficiency comparatively.

Flight muscle and flight activity of melon fly, Bactrocera cucurbitae (Diptera: Tephritidae)

The flight activity and flight muscle of the melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae) were observed. The Tethered technique was used to observe the flight activity in this study. The flight activity, and wing and flight muscles were compared between male and female melon flies. The results indicate that the female was relatively better and strong flier than the male. The mean duration of the flight activity of the females was 13.90 min/hour and of the males was 7.12 min./hour. The mean length, width, volume of wings of the males were 6.07 mm, 2.67 mm and 10.99 mm³, respectively. On the other hand, the mean length, width and volume of the wings of females were 7.07 mm, 2.87 mm and 15.60 mm³, respectively. In case of wing muscles, the mean volume of dorsal longitudinal muscle (DLM) in male and female was found 5.20 mm³ and 5.67 mm³, respectively. The mean length of flight wing muscle of male and female was 2.22 and 2.23 mm, respectively and the mean breadth of male and female was 1.65 and 1.77 mm, respectively. Dhaka Univ. J. Biol. Sci. 30(2): 179-185, 2021 (July)

Bactrocera cucurbitae (melon fly).

Considered native to India, B. cucurbitae, the melon fly, is now found in more than 40 countries. The potential risk of its introduction to a new area is facilitated by an increase in international tourism and trade, and is influenced by changes in climate and land use. After introduction, it can easily disperse due to its high reproductive potential, high biotic potential (short life cycle of 3-5 weeks, up to 10 generations of offspring per year), and a rapid dispersal ability. The economic impacts of this species result primarily from the loss of export markets and the costly requirement of quarantine restrictions and eradication measures. Furthermore, its establishment has a serious impact on the environment following the initiation of chemical and/or biological control programmes. B. cucurbitae is of quarantine significance to EPPO (European and Mediterranean Plant Protection Organization), APPPC (Asia and Pacific Plant Protection Commission), COSAV (Comité de Sanidad Vegetal del Cono Sur), CPPC (Caribbean Plant Protection Commission), and OIRSA (Organismo Internacional Regional de Sanidad Agropecuaria) countries.