Project
Habitat diversification to support biological pest control and pollination of Xinjiang pear
Many crops depend on insects for pollination and the suppression of pest populations. However, insect declines have been reported across the world, and these include pollinators and natural enemies of insect pests. Here we investigate how agricultural landscapes can be made more biodiversity friendly by the introduction of flowering plant species that can support beneficial insects.
Background
Korla fragrant pear is a valued fruit that is widely grown in the Korla, Xinjiang, China. Xinjiang pear orchards are intensively managed with high pesticide use. Establishing flowering plants in orchards that provide alternative prey, pollen, nectar and extrafloral nectar for natural enemies and pollinators may enhance pollination and natural pest control. However, it is unclear which plant flowering species are suitable to support natural enemy and pollinator communities in Xinjiang, and how the local practice of growing alfalfa in orchards influences pest suppression and pollination.
Project description
We focused on three research questions:
- Which plant species are attractive for pests, natural enemies and pollinators in Xinjiang?
- Which plant traits of service plants, such as plant height, flower area and corolla depth, are important for the attraction of natural enemies and pollinators?
- How does alfalfa cover in pear orchards influence natural enemies and pollinator communities, pest suppression and pollination of pear?
We conducted a two-year experiment where we assessed natural enemy and
pollinator communities using visual counts and sweepnetting on 39 flowering plant species. We also assessed plant height, flowering period, flower size, corolla depth and corolla width. For the third question, we selected 14 paired pear orchards with
and without alfalfa cover, and assessed pest and natural enemy communities on
pear branches by visual observation, pollinator communities by pan traps, predator activity using sentinel egg cards and pear flower visitation by pollinators, fruit and seed set and pear weight.
Results
For the first question, we found that Gossypium hirsutum (cotton), Melilotus officinalis (sweet clover), Medicago sativa (alfalfa), Anethum graveolens (cumin), and Foeniculum vulgare (fennel) were associated with relatively high natural enemy abundances, but G. hirsutum, M. officinalis and M. sativa also hosted cotton or cowpea aphids. Ladybeetles, predatory bugs and parasitoids showed positive responses to aphid densities on plants. Ladybeetle adults showed consistent positive responses to extrafloral nectar, open corollas and flowering across two years, while for other natural enemies this was only found in one out of two years.