Comparative Efficacy of Three Different Insecticides Against Adult Fruit Flies Bactrocera zonata (Saunders) (Diptera: Tephritidae) Under Laboratory Conditions

In this study commercial formulations of three commonly used insecticides namely trichlorfon 80% SP (Trichlorfon), lambda-cyhalothrin 2.5% EC (Karate), and imidacloprid 25% WP (Confidor) were evaluated under laboratory conditions to determine their comparative efficacy against newly emerged adults of Bactrocera zonata (Saunders) (Diptera: Tephritidae). These insecticides were obtained from the respective distributors in Punjab, Pakistan.

Insecticides were mixed with distilled water in 500-ml jar to get 500 ppm concentration as a stock solution, while 250, 125, 62.5, and 31.25 ppm were made by serial dilution of stock solution. Five plastic jars were treated with cotton swab dipped in specific concentration (ppm) of required insecticide and experiment was replicated thrice. Distilled water alone was used as control. Ten, newly emerged fruit fly adults were shifted into each plastic jar with help of paper within the rearing cage. Fruit flies in each plastic jar were provided with sugar hydrolysate mixture in Petri dish. Plastic jar mouth was covered with a muslin cloth with a rubber band to hold it firmly for appropriate ventilation and to prevent the escape of fruit flies. In control treatment jars were treated with the distilled water instead of insecticide concentration.

Mortality data were recorded after 24, 48, and 72 h, respectively. Irreversible knockdown followed by death of the adult fruit flies was considered standard mortality. Mortality data were converted into percentages. If mortality in control exceeded 5%, it was corrected using Abbotts formula (Rosenheim, 1989). As mortality in control treatments did not exceed 5% in these trials the correction formula was not applied. Mortality data sets by all three different insecticides were analyzed separately. Data were analyzed statistically using SPSS (version 16.0 for windows) by analysis of variance technique using mortality data as dependent variables while insecticide concentrations were taken as independent variables. Means were separated post hoc by Tukey HSD test at 5% level of probability.

Results showed that after 24 h of treatment, maximum mortality caused by imidacloprid was recorded (20.000 ± 0.000) due to 500 ppm concentration while minimum was recorded (0.000 ± 0.000) at 62.5 and 125 ppm concentration (P < 0.05). Maximum mean mortality due to lambda-cyhalothrin was recorded (86.667 ± 6.666) at 500 and 250 ppm concentration and minimum was (6.667 ± 6.666) at 31.25 ppm. Mortality due to trichlorfon remained maximum (100.000 ± 0.000) tested at all the concentrations in all the replications (SD = 0) (Table 1).

After 48 h, maximum mortality caused by imidacloprid was recorded (100.00 ± 0.000) due to 500 ppm concentration while minimum was recorded (13.333 ± 6.666) at 62.5 and 31.25 ppm concentration (P < 0.05). Maximum mean mortality due to lambda-cyhalothrin was recorded (100.000 ± 0.000) at 500 and 250 ppm concentration and minimum was (26.667 ± 6.666) at 31.25 ppm. Mortality due to trichlorfon remained maximum (100.000 ± 0.000) tested at all the concentrations in all the replications (SD = 0) (Table 2).

After 72 h, maximum mortality caused by imidacloprid was recorded (100.00 ± 0.000) due to 250 and 500 ppm concentration while minimum was recorded (60.000 ± 11.547) at 31.25 ppm concentration (P > 0.05). Mortality due to lambda-cyhalothrin and trichlorfon remained maximum (100.000 ± 0.000) tested at all the concentrations in all the replications (SD = 0) (Table 3).

These results revealed that trichlorfon is highly efficacious even after 24 h of treatment and can give quick knockdown effect against adults of fruit flies in laboratory and is recommended to be used further under field conditions for quick control of adults of B. zonata.¹

Footnotes