Comparing the ability of small-scale and large-scale habitat restorations for structuring natural enemy communities and achieving pest control in citrus and avocado

We investigated how non-crop habitat at local and landscape scales influence insect communities in citrus and avocado in Ventura, California. With significant agricultural land use and urban development in the region, understanding the ecological consequences for pest dynamics is crucial. This project examines how proximity to natural habitat (riparian restorations) and the presence of on-farm vegetation (hedgerows) affect the diversity of insect communities. We targeted key citrus and avocado pests, including avocado thrips, red scale, and Asian citrus psyllid, while comparing how their predators and parasitoids respond to habitat mosaics.
We sampled insect communities using sticky traps and PCA scouting reports at 16 citrus and avocado orchard sites varying in their proximity to restored riparian areas and in the presence of hedgerows. We found that farms closer to riparian areas hosted fewer pest species and more beneficial insect species. We used generalized linear mixed models to examine the relationship between habitat and beneficial insect populations. In lemon, a higher percentage of non-crop habitat within 1000 meters of each site was associated with a greater abundance of parasitoids and predators and a reduction in pest species richness (p< 0.05). Interestingly, non-crop habitat was not associated with reductions in avocado pest abundance and richness, possibly due to the lack of natural enemies for the major non-native avocado pests in our region. These findings suggest that small-scale habitat enhancements and broader landscape features play important roles in shaping pest control dynamics, but the impact varies by the type of crop and insects considered.