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Integrated Pest Management · Agriculture and Natural Resources

University of California

Insectary Plants

Insectary plants bordering tomato field.

Insectary plants bordering tomato field

Insectary plants are those grown to attract, feed, and shelter insect parasites (parasitoids) and predators to enhance biological pest control. Insectary plants provide nectar and pollen for adult natural enemies to consume. Even if pests are abundant, certain natural enemies may be less abundant, shorter-lived, or produce fewer offspring unless nectar and pollen resources are available. Insectary plants can also host alternate prey that will feed the natural enemies and keep them abundant locally.

Companion plants, cover crops, and hedgerows grown for other purposes can also serve as insectary plants; the terms are sometimes used interchangeably. Farmscaping is a whole-farm approach to conserving desirable species and includes using companion and insectary plants, cover crops, hedgerows, and more.

Insectary plants will not always help to reduce pest problems, and their utility varies with the crop or landscape situation. Biological pest control may be enhanced in the vicinity of insectary plants, but less so or not at all as the distance from them increases. Insectary plantings require management and take up space that might otherwise be used to grow more of the marketed crops. Other practices to protect natural enemies and pollinators and additional integrated pest management (IPM) methods generally are needed.

Planting pattern

Insectary plants can border or surround crops, edible gardens, and ornamental plants, or be interplanted in clumps or rows. How and where insectary plants are grown depends on factors such as land use, site conditions, and the extent to which the plants are intended to serve additional purposes such as windbreaks.

Species selection

Growing the right combination of plants that flower sequentially (PDF) can provide nectar and pollen for adult natural enemies throughout the year. Choose plant species and cultivars that are well-adapted to the local soil and growing environment and compatible with the growth and cultural care of the other desirable plants grown. Certain crops, edible landscapes, and aesthetically pleasing ornamentals can serve as insectary plants.

Adult syrphid feeding on pollen

Adult syrphid feeding on pollen

For recommended annual insectary plants, see Flower Flies (Syrphidae) and Other Biological Control Agents for Aphids in Vegetable Crops (PDF). For perennial insectary plant species and their management, consult Establishing Hedgerows on Farms in California (PDF).

Avoid insectary plants that host important plant pathogens or arthropod pests that can move to damage nearby crops or ornamentals. Consult the UC IPM publications on the plants you are considering for insectaries. Compare their pest species to those listed for your crops or other desirable plants grown:

Managing insectary plants

Control of vertebrate pests and weeds and at least occasional watering are required in many situations to maintain insectary plantings. For example, drought-tolerant insectary perennials can be planted in the fall before California's rainy season, irrigated every 1 to 3 weeks during the drought season for the first 3 years, then deep watered less frequently during subsequent drought seasons, depending on the plants, climate, and soil type. Mowing, pruning, removal during certain stages of crop production or harvest, and replanting or overseeding are other common management practices.

Overlapping strategies

Plants grown for other purposes can also serve as natural enemy insectaries or otherwise enhance biological pest control.

Banker plants. Hosts of plant-feeding species that are not pests of your crops or other desirable plants grown can be used to rear certain natural enemies. For example, plants infested with aphids that don't feed on the crop can be inoculated with parasites or predators that will reproduce on them. These banker plants (e.g., in containers) with nonpest aphids and parasites or predators are scattered throughout a greenhouse or nursery to provide a continual source of natural enemies that disperse to consume pests on the crops, such as for aphid control in greenhouses (PDF).

Beetle banks (PDF). Permanent strips planted with bunch grasses or other low-growing perennials shelter predatory, ground-dwelling invertebrates. Predaceous ground beetles, rove beetles, and spiders eliminated from cropped areas by cultivation, harvest, seasonal fallowing, or the application of certain pesticides will disperse from the protected mounds or strips (beetle banks) to recolonize the cropped areas.

Companion plants. Different species of plants can be grown close together for the purpose of benefiting one or more of them. Certain crops can benefit by planting other species that exclude weeds, improve soil, increase pollinator abundance, physically protect or support the crop, and increase natural enemy abundance. In addition to benefiting the primary crop, ideal companion plants can be harvested and used, such as compatible mixtures of culinary herbs, cut flowers, and vegetables.

Cover crops. Also called a floor cover or ground cover, these low-growing nonharvested plants help manage fertility, soil erosion and tilth (physical characteristics such as aeration and ease of tillage), water infiltration (drainage) and runoff and suppress weeds and otherwise enhance production of the harvested crop. Cover crops are used in vegetable production, vineyards, and tree crops such as walnuts (PDF).

Hedgerows. Strips of shrubs, trees, and other perennials bordering crops and gardens provide many benefits. These plantings can exclude undesirable weedy species, improve air quality, reduce erosion, and provide shade, wildlife habitat, and protection from wind as well as serve as insectary plants. Consult Establishing Hedgerows on Farms in California (PDF) and the list of California native perennial plants recommended for hedgerows in the Sacramento Valley.

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Wildflower plantings (PDF). Strips of forbs on field crop edges can increase the abundance and longevity of beneficial insects including bees and natural enemies.

More information

Insectary Plants
Natural Enemies
     

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