How to Manage Pests

UC Pest Management Guidelines

Weeds can be divided into broadleaf plants (dicotyledons) or narrowleaf plants (monocotyledons). Most narrowleaf plants are grasses, but this group also includes sedges such as yellow nutsedge, which are important weeds. Another way to classify weeds is by when they germinate and grow. Many common weed species are winter annuals, germinating mainly in fall, growing through winter and spring, and flowering and setting seed. Summer annuals germinate in spring, grow through summer, and flower and set seed. A few weeds complete a life cycle in 2 years and are referred to as biennials (e.g., bristly oxtongue). Some of the worst weed species (e.g., bermudagrass, creeping woodsorrel, and nutsedge) are perennials; they live for 2 years or more.

Growing site and production practices largely determine which weeds are likely to become problems at a site. For example, weeds commonly associated with container nursery production include creeping woodsorrel, common groundsel, lesser-seeded bittercress, and prostrate and spotted spurge. Sometimes pearlwort, liverwort, annual bluegrass, or willowherb are a problem. In field sites, weed species vary greatly but the weed spectrum can be influenced by management practices in the field and by the environment. Because of these variations, each type of production situation is addressed separately in this guideline. After the section on general methods of weed management, there are special sections for weed management in:

• container nurseries,
• field-grown trees and shrubs,
• field-grown flowers, and
• greenhouse-grown crops.

PUBLICATION

UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries
UC ANR Publication 3392
Weeds
C. A. Wilen, UC IPM Program, UC Cooperative Extension, San Diego County
Acknowledgment for contributions to Weeds:
C. L. Elmore, Vegetable Crops/Weed Science, UC Davis

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