Climate change is expected to significantly affect many ecosystems, the services they provide to humans, such as disease and pest regulation, and the efficiency of biological control interfaces in agriculture.
Effects of climate change on pest control are mainly studied in terms of the temporal matching between predator and prey or plant-pest interactions, while the effects on plant diseases are mainly studied in terms of plant-pathogen interactions.
There is a lack of research on the effects of climate change on disease spread rates in plant populations via insect vectors.
In the urgency of the climate crisis, it is difficult to conduct empirical studies that predict the complex processes determining ecosystem functions and disease spread patterns.
Nevertheless, by combining general theoretical models and data from the scientific literature, it is possible to quickly assess the potential consequences of different mechanisms.
Such an approach can focus empirical research efforts, which are costly, on the systems and mechanisms most likely to be significant and help understand unexpected outcomes.
There is extensive knowledge in the literature about the effects of various climate variables on insect physiology and life history traits, including many pests.
In particular, a strong positive link between temperature and insect development rate has been established, and it is estimated that a warming of 2 degrees Celsius could allow different pests to complete up to five additional reproductive cycles per season, exponentially increasing their maximum reproductive potential.
Therefore, climate warming is expected to trigger outbreaks of disease vector populations, posing risks to food supply as well as to wild and human populations.
It is more difficult to estimate the potential of natural enemies to biologically control diseases under these conditions.
To perform such an assessment, we developed mathematical models describing general mechanisms underlying the spread dynamics of two major groups of plant diseases diseases caused by persistent pathogens, which reside in the vector’s body for most of its life stages, and diseases caused by non-persistent pathogens, which survive in the vector’s body for very short periods relative to its life cycle.
Using these models, we conducted a theoretical analysis of the expected epidemiological consequences of temperature-dependent changes in vector development rates and their expected control by generalist predators, which feed on multiple food sources, and specialist predators, limited to a single food source.
The degree of specialization of natural enemies is an important axis in the functional diversity of arthropod communities and the damage control they can provide.
For example, generalist predators form the basis for a “standing army” approach in conservation biological control, in which supplying alternative food sources maintains a constant predator population that prevents pest establishment in early stages.
There is also commercial rearing of both predator types for augmentative biological control, where local releases of predators respond to pest outbreaks.
As expected, with climate warming, an increase in vector development rates may greatly enhance their ability to spread diseases, especially in systems where the limiting factor is development rate. The spread of persistent pathogens is expected to be limited to low development rates since it depends on all life stages of the vectors.
Control of both disease groups by generalist predators is not expected to be affected by changes in vector development rates due to the relative insensitivity of these predators to vector population size.
The effectiveness of such predators is highest against vectors with low development rates and increases when vector carrying capacity is enhanced by supporting resources such as nectar, pollen, and alternative prey.
In contrast, changes in vector development rates are expected to greatly enhance the ability of specialist predators to suppress disease spread, especially in systems with high baseline vector development rates.
It should be emphasized that these models are not intended for disease prediction or management, as climate change is expected to manifest in distributions of multiple climate variables and affect other physiological aspects of organisms in the system.
Nevertheless, the models provide basic expectations regarding the consequences of a well-known and central physiological aspect in insects.
Based on this and additional empirical data from the literature, specific plant diseases of key crops can be modeled in detail to refine forecasts for different control interface approaches and improve control strategies in a changing climate.