Interactive effects of temperature and CO2 on efficacy of insecticides against Spodoptera litura Fab. in a global warming context
2021
Srinivasa Rao, M. | Sreelakshmi, P. | Deekshita, K. | Vanaja, M. | Srinivas, I. | Maheswari, M. | Srinivas, K. | Sammi Reddy, K. | Bhaskar, S. | Ravindra Chary, G.
Influence of two dimensions of climate change i.e., elevated temperature (eTemp) and elevated CO₂ (eCO₂) on toxicity of insecticides against Spodoptera litura Fab. on peanut using CO₂ Temperature Gradient Chambers (CTGC) facility was investigated. The insecticides viz., diamides (flubendiamide), avermectins (emamectin benzoate), organophosphates (quinalphos), spinosyns (spinosad) and synthetic pyrethroids (deltamethrin) were tested for their efficacy and persistence toxicity (PT) at eTemp and eCO₂. The twelve set conditions comprising of reference (28 ± 0.5 °C; 380 ppm), eTemp (29, 30, 31, 32, 34 ± 0.5 ᵒC with 380 ppm CO₂), eCO₂ (28 ± 0.5 ᵒC; 550 ppm) and eTemp+eCO₂ (29, 30, 31, 32, 34 ± 0.5 ᵒc with 550 ppm CO₂) were maintained in CTGC. Interactive effects of eCO₂ and eTemp caused the higher LC₅₀ values of spinosad and deltamethrin with negative temperature coefficients and showed the ‘reduction of toxicity’. Lower LC₅₀ values and positive temperature coefficients for flubendiamide (6.67), emamectin benzoate (7.38) and quinalphos (3.04) were recorded, indicating the ‘higher toxicity’ at interactive eCO₂ and eTemp. The order in PT of insecticides was deltamethrin<quinalphos<flubendiamide< emamectin benzoate< spinosad and these insecticides persisted for shorter period at eTemp + eCO₂ conditions over reference. Present results indicate the negative impact of eTemp and eCO₂ on efficacy of spinosad and deltamethrin necessitating their higher requirement than was needed to achieve equal control at reference/ambient temperature and CO₂.
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