Fig 1.
Experimental setup for the direct spray application of MB solutions onto the whitefly-infested tomato leaves.
(A) Adults of Bemisia tabaci (less than 5 days old) from the rearing colony were collected in a group and placed on ice; (B) Batches of 25 cold-immobilized adults were placed on test leaves in breeding cups; (C) MB solutions were sprayed onto each leaf using a glass spray bottle.
Fig 2.
The apparatus used in bioassays.
Before the assay, methyl benzoate (treatment) solution was applied to the filter paper and placed between the netting screen and the bottom of the assembly, and then the tube was covered with parafilm. The opposite end of the tube was used as the control.
Fig 3.
Contact toxicity of methyl benzoate against adults of Bemisia tabaci.
For direct spray application on whitefly infested tomato leaves (A), various concentrations of MB solution (~0.5 mL total) were sprayed on < 5-d-old adults of B. tabaci (n = 20). For residual toxicity (B), various concentrations of MB solution (~0.5 mL total) were first sprayed on tomato leaves and allowed to dry for 2 h before < 5-d-old adults (n = 20) were released into an insect breeding cup containing the leaves. Values are the means of three replicates.
Table 1.
Comparing LT50 of methyl benzoate (MB) against Bemisia tabaci adults after direct spray application of different concentrations (n = 60).
Table 2.
Comparing LT50 against Bemisia tabaci adults, treated with different methyl benzoate (MB) concentrations in a residual assay (n = 60).
Table 3.
Comparative lethal median concentration (LC50) values of methyl benzoate (MB) for Bemisia tabaci eggs, nymphs, and adults.
Fig 4.
Contact toxicity of methyl benzoate against Bemisia tabaci eggs and fourth-instar nymphs.
Tomato leaves infested with 7-d-old eggs (n = 30) or 4-d-old fourth-instar nymphs (n = 15) were dipped into the various concentrations of MB solutions. Egg hatch reduction rates (A) and adult eclosion reduction rates (B) were assessed at 6 d post-treatment. Values are means of three replications. Means denoted by the same letters are not significantly different at α = 0.05 (N = 3, df = 4, 14; for ovicidal effects, F = 75.82; P < 0.0001; for nymphicidal effects, F = 83.14; P < 0.0001).
Table 4.
Efficacy of methyl benzoate against Bemisia tabaci in pot culture.
Table 5.
Fumigant toxicity of methyl benzoate determined as a percentage of Bemisia tabaci corrected mortality after 2 h, 4 h, 6 h, 8 h, and 10 h exposure in the laboratory.
Table 6.
LT50 values from fumigation bioassay of methyl benzoate (MB) against Bemisia tabaci adults for different concentrations (n = 90).
Fig 5.
Repellency effects of methyl benzoate against adults of Bemisia tabaci.
A binary-choice bioassay tube was used to determine behavioral responses of B. tabaci after encountering 0% (control), 0.1%, 0.25%, 0.5%, 1%, and 2% MB solutions. Repellency was determined at 1, 3, and 6 h post-treatment. Values are the means of three replications. Means followed by different superscript letters are significantly different at α = 0.05 (N = 3, df = 5, 17; for 1 h, F = 26.11; P < 0.0001; for 3 h, F = 29.99; P < 0.0001; for 6 h, F = 19.87; P < 0.0001).
Fig 6.
Repellency and anti-oviposition activity of tomato plants sprayed with methyl benzoate.
Tomato plants were treated with 0%, 0.1%, 0.25%, 0.5%, 1%, and 2% MB solutions. One non-treated and one treated tomato plant were placed together within a single cage before releasing 100 adults of B. tabaci. Repellency was determined through counting B. tabaci on leaves (n = 100) of both plants at 24 and 48 h post-treatment. Eggs on leaves (n = 10) of each plant were counted at 24 and 48 h post-treatment to determine anti-oviposition activity. Values are means of three replications. For (A) repellency, means marked with different superscript letters are significantly different at α = 0.05 (N = 3, df = 5, 17; for 24 h, F = 108.56; P < 0.0001; for 48 h, F = 68.20; P < 0.0001). For (B) anti-oviposition, means followed by different superscript letters are significantly different at α = 0.05 (N = 3, df = 5, 17; for 24 h, F = 231.17; P < 0.0001; for 48 h, F = 71.77; P < 0.0001).