Paper Reviewed
Shwetha, A.G.S., Ashoka, J., Nadagoud, S. and Kuchnoor, P.H. 2019. Effect of elevated CO2 and temperature on biochemistry of groundnut and in turn its effect on development of leaf eating caterpillar, Spodoptera litura fabricius. Legume Research 42: 399-404.

Introducing their study, Shwetha et al. (2019) say that climate change can "directly stimulate plant growth, affect plant resource allocation and change plant tissue quality and it is consequently predicted to indirectly affect insect-herbivory. And thus they set out to investigate the effects of predicted changes in elevated CO2 and temperature on plant herbivore interactions between peanut (Arachis hypogaea) and the tobacco armyworm (Spodoptera litura).

The experimental set up consisted of two temperature (ambient or ambient +2°C, warmed with infrared heaters) and two atmospheric CO2 (490 or 550 ppm) treatments. The peanut crops were grown in open-top chambers and larvae of S. litura were fed on fully matured peanut leaves in petri plates (later plastic jars) in each of the treatment chambers. Various measurements of insect growth and development were made throughout the course of the experiment.

Shwetha et al. report that temperature had little impact on S. litura growth, whereas elevated CO2 impacted it significantly. In particular, higher CO2 caused significant changes in leaf chemistry that altered the food quality and, ultimately, the growth, development and fecundity of this herbivore pest. More specifically, S. litura experienced increased food consumption, increased larval weight and produced more fecal matter due to extended larval and pupal duration under elevated CO2. It also experienced reduced conversion of ingested food and reduced relative growth rates, which combination of factors had a "negative effect on the growth and development of S. litura." Consequently, Shwetha et al. conclude that "the growth performance of S. litura under elevated CO2 conditions affects [this herbivore pest] badly, resulting in poor perpetuation of the population which may reduce its fitness in subsequent generations." And that should be welcomed news for growers of this key oilseed crop, who typically lose some 35-55% of their yield to this herbivorous pest.