How does atmospheric elevated CO2 affect crop pests and their natural enemies? Case histories from China

Abstract

Global atmospheric CO2 concentrations have risen rapidly since the Industrial Revolution and are considered as a primary factor in climate change. The effects of elevated CO2 on herbivore insects were found to be primarily through the CO2‐induced changes occurring in their host plants, which then possibly affect the intensity and frequency of pest outbreaks on crops. This paper reviews several ongoing research models using primary pests of crops (cotton bollworm, whitefly, aphids) and their natural enemies (ladybeetles, parasitoids) in China to examine insect responses to elevated CO2. It is generally indicated that elevated CO2 prolonged the development of cotton bollworm, Helicoverpa armigera, a chewing insect, by decreasing the foliar nitrogen of host plants. In contrast, the phloem‐sucking aphid and whitefly insects had species‐specific responses to elevated CO2 because of complex interactions that occur in the phloem sieve elements of plants. Some aphid species, such as cotton aphid, Aphis gossypii and wheat aphid, Sitobion avenae, were considered to represent the only feeding guild to respond positively to elevated CO2 conditions. Although whitefly, Bemisia tabaci, a major vector of Tomato yellow leaf curl virus, had neutral response to elevated CO2, the plants became less vulnerable to the virus infection under elevated CO2. The predator and parasitoid response to elevated CO2 were frequently idiosyncratic. These documents from Chinese scientists suggested that elevated CO2 initially affects the crop plant and then cascades to a higher trophic level through the food chain to encompass herbivores (pests), their natural enemies, pathogens and underground nematodes, which disrupt the natural balance observed previously in agricultural ecosystems.

Feeding behavior, life history, and virus transmission ability of Bemisia tabaci Mediterranean species (Hemiptera: Aleyrodidae) under elevated CO2

“…Elevated CO 2 is known to accelerate plant growth and to increase plant photosynthetic rates, plant canopy temperatures, biomass and carbon : nitrogen (C : N) ratios (Ward & Kelly, ; Oehme et al ., ; Sun et al ., ; Curnutte et al ., ; Guo et al ., ; Kimball, ; Trębicki et al ., ; Zhang et al ., ). Therefore, given that elevated CO 2 increases carbohydrate accumulation and the generation of reactive oxygen species (ROS) in plant tissues and decreases nitrogen accumulation, soluble proteins and amino acids, the plant primary and secondary metabolites as well as antioxidant and enzymatic proteins are altered, and this is likely to impact the performance and behavior of herbivores (Sun et al ., ; Sun et al ., ; Guo et al ., ; Ryan et al ., ; Trębicki et al ., ; Li et al ., ; Rajashekar, ).…”

Climate Change Impacts on Plant Pathogens and Plant Diseases

“…Increased CO 2 concentrations have different effects on aphids and whiteflies, suggesting that we cannot generalize the effects of these conditions across different pest-plant systems (Bezemer et al 1998;Cannon 1998;Sun et al 2011). These discrepancies can probably be attributed to the fact that the effects of CO 2 on vectors are mostly indirect (i.e., changes in carbon fixation rates in plants at high CO 2 levels affect C/N ratio or increased levels of phenolics and terpenes).…”

“…Interactions between increased CO 2 levels and higher temperatures have also been noted in some insect-plant systems (Zvereva and Kozlov 2006). Although elevated CO 2 levels have been shown to have little direct effect on natural enemies of insect herbivores, they can influence the third trophic level indirectly, by altering the size and composition of populations of prey insects available to predators and/or by disrupting developmental synchrony for parasitoids (Sun et al 2011) to affect virus transmission.…”

Accumulation of Urban Insect Pests in China: 50 Years’ Observations on Camphor Tree (Cinnamomum camphora)

“…Natural and anthropogenic factors have resulted in altered environmental conditions that influence changes in abundance and diversity of insect pests [22], which then possibly affect the intensity and frequency of pest outbreaks on host plants [23]. The C. camphora-hosted insect pest outbreak dataset that was compiled are multi-proxy datasets of pest complexes on camphor trees.…”