Toxicity of thiamethoxam and imidacloprid to Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) nymphs associated to aphid and whitefly control in cotton
Torres, J.B. | Ruberson, J.R.
The toxicity of thiamethoxam and imidacloprid to Podisus nigrispinus (Dallas) nymphs, and their efficacy against whitefly and cotton aphid were studied. Thiamethoxam and imidacloprid were 217.6 and 223.4 and 1435.2 and 346.8 times more toxic (LC90) by ingestion than by residual contact to 2nd- and 5th-instar nymphs of this predator, respectively. Nymphs caged on potted cotton plants and treated with either insecticide at 1 mg (a.i.) per plant or more had lower survival than those on untreated plants, up to day 52 after treatment. Thiamethoxam and imidacloprid reduced field survival of P. nigrispinus compared to untreated plants up to nine days after treatment. Thiamethoxam and imidacloprid showed significant control of whitefly in comparison with untreated plants up to 40 days after treatment in potted plants. Whitefly population had low density over time in the field with no differences between treatments and only at day 64 higher whitefly population was observed on untreated plants and plants treated with 0.5 mg (a.i.) of thiamethoxam per plant. Plots treated with thiamethoxam and imidacloprid at doses over 1 mg (a.i.) per plant retained aphid infestation lower than 10% up to 61 days of plant age. Untreated and treated plants with 0.5 mg of thiamethoxam showed infestation of 68.7 and 31.2%, respectively, at this time. Thiamethoxam and imidacloprid used in cotton for whitefly and aphid control aiming P. nigrispinus preservation can be more successful when they are used at doses bellow 1 mg (a.i.) per plant due to shorter residual effect.
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