Managing Habitat for Pollinators

Native pollinators clearly help with crop pollination, yet many agricultural areas lack the habitat necessary to support native pollinators. Proximity to natural or semi-natural land is often an important predictor of pollinator diversity in cropland. For agricultural areas that have lost native pollinators due to habitat modification or pesticide treatments, adjacent natural areas provide two valuable benefits. First, they are a source of pollinators for crop pollination. Second, they act as refugia for pollinators that can recolonize degraded agricultural areas. View in-depth guidelines for managing pollinators in natural areas.

Another valuable resource is the Yolo Natural Heritage Program (NCP/NCCP) Pollinator Conservation Strategy. Written by Xerces Society scientists, this first-of-its-kind conservation strategy summarizes the threats facing native bees and identifies conservation measures that can be taken within diverse landscapes, including agriculture, grasslands, woodlands, shrubland, riparian, and urban.

Management tools, such as grazing, fire, and mowing, can be used in a manner that benefits pollinators. The use of insecticides and herbicides can be harmful to pollinators; if they must be used, there are a few considerations to minimize their impact on pollinators.

Grazing

Consider timing, duration and intensity
A diverse pollinator population requires adequate nectar and pollen sources from early spring to early fall, which makes seasonal timing a key consideration for an effective grazing plan. Management should be adjusted to maintain the majority of the floral resources throughout the seasons. Also, grazing should be avoided when butterfly larvae or adults are active, as it can result in direct mortality. Grazing periods should be short to allow for adequate recovery of the habitat. Herd sizes should be moderate to light.

Fire
Consider scale and refugia
While prescribed burning has a role to play in long-term maintenance of pollinator habitat, it can also have catastrophic impacts on pollinators. To minimize negative impacts, a single fire should not burn an entire area of pollinator habitat. Ideally, a program of rotational burning in which small sections—30 percent of a site or less—are burned every few years will ensure adequate colonization potential and refugia for insects.
Mowing
Consider technique, timing and scale
Mowing can cause direct insect mortality, especially for egg or larval stages that can’t avoid a mower. Ideally, mowing should occur in the fall or winter when flowers have died or are dormant. Mowing a mosaic of patches over several years is better than mowing an entire site all at once; no single area should be moved more than once a year.
Herbicides
Consider application method and active ingredients
While herbicides can be an important management tool, broadcast applications of non-selective herbicides can reduce important floral resources. To avoid herbicide damage to nontarget plants and associated pollinators, avoid broadcast spraying or pellet dispersal, which may kill large numbers of larval hostplants or adult forage plants. Instead, spot treat with a backpack sprayer, allowing for selective control.
Insecticides

Consider application method, product formulation, and timing
Insecticides used on forests, rangelands and farms can severely impact pollinator populations. In situations where insecticides must be used, it is best to avoid spraying when flowers are in bloom. Choose less harmful formulations—in general dusts and microencapsulated insecticides are the most dangerous formulations for bees, and aerial spraying is the most harmful method of application. Sprayed solutions and large granules tend to be less harmful to pollinators. Pay attention to the potential presence of butterfly hostplants in the management area and avoid spraying them.

Oregon State University, Washington State University and the University of Idaho Extension have developed a comprehensive guide, available as a pdf: How to Reduce Bee Poisoning from Pesticides.

The Xerces Society • 628 NE Broadway Ste 200, Portland OR 97232 USA • tel 855.232.6639 • fax 503.233.6794 • info@xerces.org
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