Impact of climate on a host-hyperparasite interaction on Arabica coffee in its native range

Natural enemies of plant pathogens might play an important role in
controlling plant disease levels in natural and agricultural systems. Yet,
plant pathogen-natural enemy interactions might be sensitive to climatic
changes. Understanding the relationship between climate, plant pathogens,
and their natural enemies is thus important for developing
climate-resilient, sustainable agriculture. To this aim, we recorded shade
cover, daily minimum and maximum temperature, relative humidity, coffee
leaf rust, and its hyperparasite at 58 sites in southwestern Ethiopia
during the dry and wet season for two years.  Coffee leaf rust
severity was positively related to the maximum temperature. Hyperparasite
severity was higher when the minimum temperature was low (i.e. in places
with cold night temperatures). While canopy cover did not have a direct
effect on rust severity, it reduced rust severity indirectly by lowering
the maximum temperature. Canopy cover had a direct positive effect on the
hyperparasite severity during one surveying period.  Synthesis
and applications. Our findings highlight that coffee leaf rust and its
hyperparasite are both affected by shade cover and temperature, but in
different ways. On the one hand, these niche differences lead to the
worrying prediction that levels of coffee leaf rust will increase, and its
hyperparasite will decrease, with climate change. On the other hand, these
niche differences between coffee leaf rust and its hyperparasite provide
opportunities to develop strategies to manage the environment (such as
shade cover and microclimate) in such a way that the rust is disfavored
and the hyperparasite is favored.