Bottom-up effect on top-down control in a suburban landscape
Date
2010
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Publisher
University of Delaware
Abstract
Conservation biological control aims to attract and maintain populations of pest-reducing natural enemies by way of alternative prey. By using plants with which native insect herbivores share an evolutionary history, homeowners may reduce the need for pesticides by supporting prey and thus, their enemies. To test this prediction, six pairs of properties, one landscaped with native ornamental plants and the other with non-natives, were studied. The abundance and diversity of arthropod communities, the effectiveness of natural enemies, and the degree of aesthetic injury to landscape plants were compared in 2008 and 2009. I found moderate evidence to support the prediction that pest populations will remain lower and more stable in native-based landscapes. Native properties supported a higher diversity of herbivores and natural enemies in the herbaceous layer than properties landscaped with non-native plants. Alternatively, a higher abundance of these guilds were found in non-native landscapes than native ones. These differences did not significantly affect insect herbivore survival; but aesthetic injury to landscape plants, especially that caused by leaf-chewing insects, was higher in properties landscaped with non-natives. This may be due to the attractiveness of native landscapes to birds, insect predators and parasitoids that suppress pest outbreaks.