Habitat creation and conservation are critical to supporting pollinators in our ecosystems, and though there are many benefits to this, sometimes it can be challenging to bring habitat into human systems.
For example, pollinator habitat near our urban or farm fruit crops increases pollination services and reduces pesticide requirements, but can also pose some economic risk if the habitat harbors harmful pests. Planning pollinator habitat plantings around landscaping guidelines and potential pests can help gardeners and farmers both create and conserve pollinator habitat.
“Alternative host” plants can harbor pests
As a pollinator habitat specialist, I work with fruit farmers in the Pacific Northwest who want to support pollinators by establishing more habitat in their working lands. When I first meet the farmer, we spend time together in their truck, winding through the orchard and landscape, spotting forgotten corners or weedy hillsides that are ready to grow flowers. We stop to take pictures and observe plant species. We also talk about what could be there and how to begin the planting process. It is important to consider what both the farmer and their neighbors are growing as this will change what and where we plant.
Some of the most destructive pests of apple, pear, blueberry, and cherry can complete their life cycle with the help of native plants. These plants are called alternative hosts. I don’t want to create a mile-long hedgerow with a pest’s alternative host because that would increase the risk of economic damage to the farmer’s livelihood. Instead, we select plants that won’t harbor harmful agriculture pests but still bloom for pollinators. Understanding the relationships between alternative hosts and pests is important in carefully selecting plants in both agricultural and gardening contexts.
Skip these plants to give Pacific Northwest fruit pests the boot
The greatest barrier to planting habitat in my region is the fear of three pests: the codling moth, spotted wing drosophila, and leafhoppers. Here is how I change my habitat-planting strategy for each one.
The codling moth (Cydia pomonella) is a non-native species that, as a caterpillar, burrows into apples and pears, making them unsellable. This is the insect responsible for emotionally scarring many of you when, after a big bite of an apple, you saw half a wriggling caterpillar in the remaining fruit. This moth’s alternative hosts are crabapple and hawthorn, so I don’t plant these genera near apple and pear orchards. There are still plenty of native plants to select from after this restriction, and I am able to plant at least three species per season to maintain consistent blooms from spring to fall. Farmers have a good toolbox for controlling codling moths, but alternative hosts can disrupt the whole region, resulting in more chemical sprays and reduced crop success.
Spotted wing drosophila (Drosophila suzukii) is another invasive species that is relatively new to the U.S.. Unlike other fruit flies, spotted wing drosophila can damage stone fruit and berries still ripening on the tree or bush. If a farmer finds just one fly, they will need to use chemical sprays to prevent major losses. The alternative host for this fly is any soft fruit, including popular hedgerow genera: mahonia (Berberis spp.), currant (Ribes spp.), snowberry (Symphoricarpos spp.), and more. I avoid these soft-fruited plants and instead plant things with a “dry” fruit that can’t host the fly, such as red stem ceanothus (Ceanothus sanguineus), shrubby cinquefoil (Dasiphora fruticose), shinyleaf spirea (Spiraea lucida), and rabbitbrush (Chrysothamnus viscidiflorus and Ericamerica nauseosus).
Leafhoppers carrying X-disease phytoplasma are the newest issue for stone fruit crops in my region. X-disease phytoplasma has many alternative hosts as it can live in most broadleaf plants. Native leafhoppers transfer the phytoplasma into new hosts, such as cherries, causing small and bitter fruit. Infected trees must be removed as there is no cure. Research on leafhopper transmission and dispersal, and how native plants fit into this picture is still in progress. In this developing scenario, the best policy is open communication with the farmer to see if their orchard is at risk and if they can plant habitat further away from vulnerable trees. Or, if they already have pollinator habitat close to the trees, I suggest habitat maintenance in times when leafhoppers have low infection rates (early summer and winter). I also follow the current research on common pests and alternative hosts in my region by checking university extension updates and recommend others do the same.
We're here to help
Balancing your needs as a farmer or gardener with those of pollinators can be a challenge, but balance is key to creating permanent habitat. Xerces can help you establish pollinator habitat while considering important pest management strategies. It’s a pleasure to work with farmers and gardeners alike who want to help our pollinators, and we are always more successful in the long term when we consider both human and invertebrate needs.
- Reducing pesticide use and impacts
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