Data from: Biological control in winter: novel evidence for the importance of generalist predators

1. The role of generalist predators in pest control has been neglected
because generalists are not able to track pest populations. Generalist
predators are suggested to be important in spring before specialist
predators become active. 2. Here, we show that some generalist predators
are important even during winter, when the majority of arthropod pests and
their enemies are dormant. We quantified the role of winter-active
generalist predators on the suppression of pear psylla during winter using
a discrete nonlinear model of an intraguild predation system. 3. To
parameterize our model, we conducted a series of experiments on (i)
functional responses, (ii) prey preferences and (iii) ontogenetic
development and made observations on the population densities of spiders
and potential prey. We ran the model for different winter scenarios, that
is, for very cold and very warm winters. 4. Synthesis and applications. We
found that winter-active predators considerably suppressed the pear psylla
population. Predators exerted a stronger effect in a warmer winter than in
a colder one. Orchard growers thus should avoid use of non-selective
pesticides during this period and instead aim to support the community of
generalist predators. Our results suggest more attention should be given
to encouraging generalist predator populations in other systems, even in
periods when crops are not producing.