- Author: Cheryl A. Wilen
Nurseries and garden centers often sell a wide range of plants for use in gardens and landscapes. As a consumer, you may manage a complex array of different landscape plantings, including woody trees and shrubs, woody ground cover beds, annual flower beds, herbaceous perennial beds, and mixed plantings. This complexity often makes weed management difficult. An integrated approach is the most economical and efficient way to control weeds, so knowing strategies for managing weeds in a variety of landscapes can help.
Woody Trees and Shrub Beds
Control perennial weeds before planting, although weed control can also be done after planting. Densely planted areas will reduce weeds. Geotextile (landscape) fabrics rather than black plastic used with a shallow layer of mulch will keep weeds from emerging. If you mulch without a geotextile base, the mulch layer must be thicker to prevent weed emergence.
If needed, you can use a preemergence herbicide to control annual weeds and supplement with hand weeding and spot applications of postemergence herbicides for weeds that are not well-controlled by hand weeding, such as perennial grasses.
Woody Ground Cover Beds
Mature, woody ground cover beds should exclude most weeds; however, when ground cover is just establishing, weed growth is likely. Perennial weeds must be controlled before planting, although perennial grasses may be selectively controlled after planting with a grass-selective herbicide like sethoxydim (Grass-Getter). Annual weeds may be controlled with mulch plus a preemergence herbicide but rooting of stolons in new plantings may be affected. You will need to supplement with some hand weeding.
Annual Flower Beds
A dense planting in annual flower beds will help shade out and compete with many weeds. Flower species should be carefully selected for weed management compatibility. Periodic cultivation at 3- to 4-week intervals and between flower beds plant rotations will also suppress weeds. Perennial weeds must be controlled before planting. Annual weeds can be controlled with mulches, preemergence herbicides, frequent cultivation, and/or hand weeding. Control perennial grasses with grass-selective herbicides like clethodim, sethoxydim, or fluazifop. Avoid nonselective herbicides in annual flower beds after planting.
Herbaceous Perennial Beds
Weed management options in herbaceous perennial beds are similar to those for annual flowers, except that it is more important to eradicate perennial weeds as there will be no opportunity to cultivate or renovate the bed for several years; and fewer species are included on herbicide labels. Geotextiles may be used in these types of plantings. Manage weeds with mulches and supplement with hand weeding. If needed, use preemergence herbicides after hand weeding.
Mixed Plantings of Woody and Herbaceous Plants
Weed management in mixed plantings is complex because of the diversity of species. Different areas of the bed could receive different weed treatments. Site preparation is critical because post-plant herbicide choices are few. Plant the woody species first and control perennial weeds in the first two growing seasons, then introduce the herbaceous species. Plant close together to shade the soil. Group plants within the bed that will receive similar weed management programs.
In most landscape situations, herbicides should not normally be needed by home gardeners. Mulching, removal by hand, and proper irrigation (pattern and amount of water) are sufficient in most cases. Find more information in the UC IPM Pest Notes: Weed Management in Landscapes.
[Originally published as "Managing Weeds in Landscapes" published in the Fall 2018 issue of the Retail Nursery and Garden Center IPM News.]/h2>/h2>/h2>/h2>/h2>
- Author: Karey Windbiel-Rojas
[From October 2013 issue of the Retail Nursery and Garden Center IPM News.]
Traps and physical barriers can be excellent tools for detecting, catching, or preventing pest invasions. Most retail nurseries and garden centers carry a variety of these types of tools, often displayed together with other products to help customers implement a multi-pronged IPM program to most effectively manage their pests.
Traps may be used to monitor or detect a pest population, to catch and identify the pest, to reduce local pest density, or more than one of these functions. Commercial traps are available for controlling or detecting various moth species (pheromone traps), whiteflies and thrips (sticky traps), flies and yellowjackets, snails and slugs, bed bugs, spiders, cockroaches and many other pests.
Pheromone traps use attractants produced by an organism to affect the behavior of other members of the same species. These traps usually have a sticky surface or chamber for catching the pests. Pheromone traps are often most useful in monitoring the presence, location, or activity of pests but may not actually reduce pest numbers, so it's critical to use the traps along with cultural, biological and chemical control methods as needed. Common pheromone traps include those for codling moth, clothes moths, pantry moths, and german cockroaches.
Many sticky traps, such as those for whiteflies, thrips, spiders, cockroaches, or fungus gnats, don't use a lure or chemical pheromone to attract the pest, but instead intercept crawling or flying pests in areas they travel. Other traps that use a food or a chemical lure to attract flies or yellowjackets can help reduce these nuisance pests around the yard. Commercially available snail and slug traps can be baited using beer or a water/sugar/yeast mixture.
Depending on the pest, you may need to place several traps around the home or landscape to determine the pest's location or level of infestation. Traps should be checked frequently and changed if necessary.
Barriers and Screens
Sometimes the best way to prevent pest damage is to keep the pests away with physical barriers. Caulking up cracks in homes and structures or installing door sweeps can exclude spiders, ants, and other crawling insects from getting inside. Keep ants out of trees and shrubs by applying sticky barriers such as Tanglefoot to the trunks. Install copper barriers to keep snails and slugs from reaching plants in raised beds or from climbing up trees.
Place row covers, hot caps, and other types of plant cages over young plants to keep pests out. Covers can be removed after the sensitive seedling stage or left on for added protection from insects and birds.
Ask your home improvement store for assistance in finding items to help repair or replace openings and holes in window and door screens. Properly maintained screens help keep an array of flying or crawling pests such as ants, flies, mosquitoes, spiders, and rodents out of the house.
Use as part of IPM
It's important to use these tools in conjunction with other methods such as cleaning up attractive food sources (rotten fruit, pet food spills, garbage); removing clutter, weedy areas, and other hiding places that may harbor pests; hand-picking or hosing off pests; properly irrigating, fertilizing, and pruning plants; and if needed, applying a pesticide that targets that pest but doesn't harm people, pets, beneficial organisms, or the environment
For information about specific pests and how traps and barriers are effective in managing them, visit the UC IPM Website at www.ipm.ucanr.edu.
Modified from “Using Traps and Barriers for Insects and Other Pests” from the Retail Nursery and Garden Center IPM Newsletter, Vol. 3, No. 3, October 2013.