Effect of alternating temperatures on food utilization of tomato fruit borer, Helicoverpa armigera

Abstract

Aim: The following study was undertaken to record the trend of approximate digestibility and efficiency of conversion of ingested food into body substance during larval stage of tomato fruit borer, Helicoverpa armigera (Hübner) due to rise in alternating temperatures. Methodology : The experiment was conducted under digitally controlled walk-in-type plant growth chamber. The impact of six alternating temperatures (Max : Min) viz. 25:10, 25:13, 25:16,30:10, 30:13 and 30:16°C were studied on approximate digestibility and efficiency of conversion of ingested food into body substance of three final larval instars of H. armigera on tomato crop. Various observations like food consumption, weight of feces and larval insect were recorded daily till pre-pupal stage and recorded data were used in mathematical equations to calculate approximate digestibility and efficiency of conversion of ingested food into body substance. Results : Both, approximate digestibility and efficiency of conversion of ingested food into body substance values responded with respect to change in alternating temperatures. Approximate digestibility values followed an increasing trend from 8.675 to 31.432 % with increase in temperature from 25:10 to 25:16° C. The increasing trend of approximate digestibility continued with rise in temperature from 30:10 to 30:16° C. However, efficiency of conversion of ingested food into body substance values declined gradually from 14.993 to 9.371 % with rise in temperature from 25:10 to 30:16°C. Interpretation: The study suggest that in the event of rising temperature under climate change, H armigera would better digest the tomato fruit but would be less efficient to convert ingested tomato fruit into body substance.