- Author: Jeannette Warnert
Cockroaches, ants and flies are three common outdoor pests that will enter homes when they have the opportunity, said UC Cooperative Extension urban integrated pest management (IPM) advisor Andrew Sutherland.
Oriental cockroaches, usually black or dark brown, are found throughout the U.S. They live and breed in dark, damp outdoor locations. Reddish-brown Turkestan cockroaches, originally from central Asia, are now well established in California. They live outside eating decaying plant and animal matter, finding safe harbor in water meter, irrigation and electrical boxes, cracks and crevices. American cockroaches live in warm and humid underground structures, such as sewers and storm drains.
If your home isn't well-sealed, they will walk right in.
Sutherland recommends using IPM strategies to prevent cockroach infestations, starting with prevention. Reduce moisture around the home, especially within the first couple of yards of the perimeter. Remove as much food as possible from around the home.
“You never want to leave pet food outside. If you have a fruit tree, make sure the fruit is not accumulating in the yard,” he said.
Add door sweeps or door brushes to close the gap underneath doors. Garages should be sealed with a flexible threshold seal.
“Spraying cockroaches with pesticides will not fix the problem,” he said. “If you have exterior doors with a one-inch gap, it doesn't matter how many pesticides you apply to cockroaches, they are still going to come in through the door. If you want to treat cockroaches with pesticides, bait works best.”
Readily available gel and granular baits are very effective.
Argentine ants are native to South America, but they have been introduced all over the globe. The tiny black insect lives in large colonies, so their trails can resemble crowded superhighways. Researchers have discovered that they tend to enter homes two times of the year: When the first rain of the season floods their nests, and when it is hot and dry in the summer.
“Sometimes they will even move their entire brood into a protected area indoors, within a wall or cabinet void,” Sutherland said. “Argentine ants live and breed outside. If you're seeing them indoors, it's because they are foraging on a resource or they're temporarily moving their colony to avoid inhospitable conditions.”
The best control strategy is prevention. Irrigated landscape favors Argentine ants. A drought-tolerant or xeriscape landscape will be less attractive to them. Removing food sources is more difficult with ants. Sap-sucking insects like aphids, mealybugs, whiteflies and soft scale deposit a sweet, sticky residue that ants love.
“If you're able to control the sap-sucking insects, you'll control the ants. Likewise, if you control ants, you'll probably see a reduction in sap-sucking insects,” he said.
Sutherland suggests avoiding regular pesticide spray programs for pest control because of the ecological damage that results when runoff flows into storm drains, creeks and other waterways. As with cockroaches, baits can be very effective.
“Ants are social insects. If an ant consumes a bit of insecticidal bait, it's going to share it with its nestmates. With baits you can actually kill an entire ant colony, where with sprays, at best you're going to kill the ants that cross chemical,” Sutherland said.
Sometimes, you might have an “ant emergency,” a swarm of ants that suddenly appears inside.
“There are safe steps to take,” Sutherland said. “I keep a spray bottle with a 10% soap solution. I spray it wherever I see ants and wipe them off. This works better than a contact insecticide because you also erase the pheromone trail the ants are using to find food or water. “
Many species of colorful metallic blowflies are found the world over. To control them, turn to prevention.
“Blowflies really like pet waste,” Sutherland said. “One deposit of waste can sustain a lot of flies. If you have pets, pick up and dispose of their waste.”
As a secondary control, be diligent with structural exclusion. Make sure the doors are closed, window screens are in good repair and screen doors fit well. You can buy aerosol cans of insecticide in home stores, which kills on contact as insects fly through mist. But it is cheaper and safer to kill them with a fly swatter or rolled up paper.
Learn more:
Summertime Household Pests, by Andrew Sutherland, UC IPM webinar on YouTube
UC IPM Pest Notes:
Cockroaches
Ants
Flies
Dozens of other pests
- Author: Cynthia Zimmerman
"We're not talking about one hungry plant here, we're talking about world conquest." – Seymour, Little Shop of Horrors.
There can be undesirable consequences to the establishment of invasive species. Invasive weeds often are responsible for drastic changes to native ecosystems, such as interfering with natural habitat and food sources for animals, causing wildfires to be more frequent and intense, and lowering water tables by invasive trees that have deep rooting systems. Some plants even alter soil chemistry making it difficult for natives to survive.
These invasive species move out of their home ranges into new areas either by wind, birds or animals, or with human assistance that may be deliberate or accidental. This has been happening since the beginning of time. Humans have deliberately, and at times inadvertently, moved plant species from one region to another. With the development of high speed travel that doesn't take months to circumnavigate the globe, plants move with ease into areas where they were never before known. At times, plants that were once desirable and beneficial while under human control in gardens become a problem as they escape and start to colonize and breed in areas where they are not wanted. According to the California Invasive Plant Council, “The spread of invasive plants is one of the most significant threats to the native plant species and vegetation communities of the state, second only to habitat destruction.”
It's up to all of us to take some responsibility for reducing the problems caused by invasive species. One simple step is careful selection of garden plants by using species that are not likely to be invasive. The following plants are at the top of the list of invasive plants that should not be planted in California:
- Pampas grass (Cortaderia selloana)
- Green fountain grass (Pennisetum setaceum)
- Mexican feather grass (Stipa/Nassella tenuissima)
- Highway iceplant (Carpobrotus edulis)
- Periwinkle (Vinca Major)
- Yellow flag iris (Iris pseudacorus)
Instead of the above listed plants, try the alternatives shown on the Plant Right invasive plant website.
For a list with pictures of suggested non-invasive plants for California, take a look at Plant Right's better plant choices.
For further information about invasive plant species and what you can do to help, see the following websites:
Don't Plant a Pest! Central Valley
Don't Plant a Pest! California Invasive Plant Council (cal-ipc.org)
Invasive Plant Checklist for California Landscaping (pdf)
The 39 Most Invasive Plant Species in California
16 Invasive Species Sold at Garden Centers You Should Never Buy
Native Plants and Invasive Species
(Originally written April 2021. Updated May 2024)
- Author: Jeannette Warnert
The summer months in Fresno County are ideal for garden soil solarization, an environmentally sound way to kill weeds, insect pests and soil pathogens with free and naturally abundant solar energy. No pesticides are used in the process.
The greenhouse effect of the sun's rays on clear plastic can heat up the top 12 to 18 inches of the soil to as high as 145 degrees under perfect conditions. Excellent pest control can be achieved by maintaining the soil at 110 to 125 degrees in the top 6 inches, according to the UC Integrated Pest Management Program. The hot soil environment will kill such pests as nematodes, grubs, cutworms, beetles and snail eggs. Disease pathogens, such as fungi that cause verticillium and fusarium wilt, die.
There are downsides. Solarization requires taking garden space out of production during the growing season for 4 to 6 weeks, but future garden success is likely worth the sacrifice. The process may also kill some beneficial soil organisms, though UC IPM reports that many beneficials survive solarization or quickly recolonize the soil afterward. Earthworms, often present in healthy soil, burrow deeper to escape the heat and return when the treatment ends.
To solarize soil, smooth an area and water uniformly to 12 inches deep, then cover it with clear plastic. Rolls of clear plastic “drop cloth” are available in the paint sections of large home stores and online. Thin plastic (1 millimeter) provides greater heating but is susceptible to tearing; slightly thicker plastic (1.5 to 2 millimeters) is better for windy areas. Secure the plastic tightly over the soil with shovelfuls of soil, lumber, rocks, landscape staples or anything that will keep the breeze from catching the edges. Leave the area undisturbed for 4 to 6 weeks or longer in cooler temperatures or if the area is shaded part of the day.
After solarization, the bed can be planted immediately with seeds or transplants.
Fresno County Master Gardener Emily LaRue is solarizing a garden bed at the program's demonstration garden, 1750 N. Winery Ave., Fresno. The Garden of the Sun is open to public visitors from 9 to 11 a.m. Mondays, Wednesdays and Fridays.
For more information on soil solarization, see the UC IPM Pest Note: Soil Solarization for Gardens & Landscapes.