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Top 10 pests in gardens and landscapes and how to control them

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1. Ants

Most people deal with ants around their home at some point. Because most ants live outdoors, focus efforts on keeping ants from entering buildings by caulking entryways. Follow good sanitation practices to make your home less attractive to ants. Spraying ants inside the home will not prevent more ants from entering. Use baits to control the ant colony. Pesticide baits work by attracting worker ants who then take the poison back to the nest where the entire colony, including queens, can be killed. In the landscape, ants protect honeydew-producing pest insects from predators, so use sticky barriers or insecticide baits to keep ants out of trees and shrubs.


2. Aphids

Aphids can curl leaves and produce sticky honeydew, but they rarely kill plants and you usually can wash them off with water. When aphid numbers get high, natural enemies such as lady beetles (lady bugs), lacewings, syrphid fly larvae, soldier beetles and others frequently feed on them, eliminating the need for pesticides. Protect these good bugs by avoiding the use of insecticides that can be toxic to a broad variety of insects. Ants protect aphids from these natural enemies, so keep ants away from your garden as well. When pesticides are necessary, use less toxic products such as insecticidal soaps and oils.


3. Asian citrus psyllid and Huanglongbing disease

The Asian citrus psyllid (ACP) and the deadly bacterial disease it spreads, Huanglongbing (HLB), threaten citrus trees in backyards and on farms. There is no cure or effective control method for HLB disease.  All types of citrus—including oranges, grapefruit, lemons, and mandarins—are affected as well as a few closely related ornamentals. ACP and HLB have already devastated the Florida citrus industry, and now that it is in the Western U.S. it is threatening the California citrus industry as well.


4. Gophers

Gophers are small burrowing rodents that feed on roots of many types of plants. A single gopher can ruin a garden in a short time, and gopher gnawing can damage irrigation lines and sprinkler systems. In lawns, their mounds are unsightly and interfere with mowing. Early detection is critical to prevent damage. Use both traps and underground fencing to manage gopher problems. Toxic baits are available but can pose threats to wildlife, pets, and children, especially in backyard situations.


5. Leaf-feeding caterpillars

Caterpillars, which are the larvae of butterflies and moths, damage plants by chewing on leaves, flowers, shoots, and fruit. Caterpillars in fruit or wood can be difficult to manage because they are hidden most of their life and can cause serious damage even when numbers are low. However, many plants, especially perennials, can tolerate substantial leaf damage, so a few leaf-feeding caterpillars often aren't a concern. Handpicking and beneficial predators and parasites often provide sufficient control. Look for feeding holes, excrement, webbed or rolled leaves, caterpillars, eggs, and good bugs.


6. Peach leaf curl

Peach leaf curl is a fungal disease that affects only peach and nectarine trees. Distorted, reddened foliage in the spring is a distinctive symptom. New leaves and shoots thicken and pucker and later may die and fall off. An infection that continues untreated for several years can lead to a tree's decline. To prevent peach leaf curl, treat peach and nectarine trees with a copper fungicide every year after leaves fall. After symptoms appear in the spring, any treatment will not be effective. When planting new trees, consider buying peach tree varieties that are resistant to the disease.


7. Rats

Rats eat and contaminate food, garden produce, and fruit, and transmit diseases to humans and pets. Manage rats by removing food and shelter, eliminating entryways into buildings, and trapping. Snap traps are the safest, most effective, and most economical way to trap rats. For Norway rats, place traps close to walls, behind objects, in dark corners, and in places where you have found rat droppings. For roof rats, place traps in off-the-ground locations such as ledges, shelves, branches, fences, pipes, or overhead beams. Ensure traps are out of reach of children and pets.


8. Scales

Scale insects suck plant juices and are pests of many trees and shrubs. Infestations can cause yellowing or premature dropping of leaves, sticky honeydew, and blackish sooty mold. Plant parts can distort or die back, depending on the species and abundance of scales. Most plants tolerate low to moderate numbers of scales. Provide plants with proper cultural care, especially irrigation. Encourage scale predators such as lady beetles or lacewings and look for parasite emergence holes in scale covers. Use sticky barriers or insecticide baits to selectively control scale-tending ants. Consider replacing problem-prone plants because most scales are highly specific to certain plants.


9. Snails and slugs

These slimy mollusks emerge from hiding at night and chew holes in leaves and flowers of many succulent garden plants and fruit. Management requires a vigilant and integrated approach that includes eliminating moisture and hiding spots, trapping, setting up barriers, and handpicking. Regularly remove snails from shelters you can't eliminate such as low ledges on fences, undersides of decks, and meter boxes. Place traps in your garden and dispose of trapped snails and slugs daily. Reduce moist surfaces by switching to drip irrigation or watering in the morning rather than later in the day. Consider snail-proof plants such as impatiens, geraniums, begonias, lantana, nasturtiums, and many plants with stiff leaves and highly scented foliage such as sage, rosemary, and lavender.


10. Weeds in landscapes

Prevent weed invasions in new beds with good site preparation. Keep weeds out with an integrated program that includes competitive plants, mulches, and hand removal. Be particularly vigilant about removing aggressive perennial weeds. You rarely should need herbicides in established landscape plantings. Mulches prevent weed seed germination by blocking sunlight. Remove small weeds by hand before they flower and set seed. Use shallow cultivation or hoeing to remove annual weeds from ornamental plantings. Only use herbicides for special-problem situations before establishing new plantings or for difficult-to-control perennial weeds.


To see all of the University of California's Statewide Integrated Pest Management Program's information on home, garden, and landscape pests, visit

For other short pest “Quick Tips” like the ten above, see

 To read even more in-depth, peer-reviewed information on many other common home and landscape pests in California, see the Pest Notes series at

Download your free UC IPM Quick Tips Booklet of the Top Ten Pests in Gardens and Landscapes and How to Control Them with the link below! 

Posted on Friday, June 10, 2016 at 12:30 PM
  • Author: Tyler Ash

Don’t feed wild animals, says UC ANR pest expert

Squirrels carry fleas that transmit plague.
Did you know that it is illegal to feed wildlife? As tempting as it is to put out bread crumbs for birds or deer chow for Bambi, there are downsides to feeding wild animals, says a UC Agriculture and Natural Resources expert in human-wildlife conflict resolution.

California law states: “Except as otherwise authorized in these regulations or in the Fish and Game Code, no person shall harass, herd or drive any game or nongame bird or mammal or fur-bearing mammal. For the purposes of this section, harass is defined as an intentional act that disrupts an animal's normal behavior patterns, which includes but is not limited to, breeding, feeding or sheltering. This section does not apply to a landowner or tenant who drives or herds birds or mammals for the purpose of preventing damage to private or public property, including aquaculture and agriculture crops.”

Feeding wild animals may help non-native, invasive, nuisance and feral animals survive, says Niamh Quinn, UC ANR Cooperative Extension advisor in San Diego and Los Angeles counties.

“Many of these species have public health risks associated with them, which can cause serious illness in humans,” Quinn said. “Rats and squirrels carry fleas that transmit plague and feral cats also carry fleas that carry typhus. Both of these diseases can be transmitted to people and cause serious illness, or even death.”

During the summer of 2015, two tourists at Yosemite National Park contracted plague, but humans are not the only ones at risk from disease. Wildlife can also become more exposed to disease as a result of people feeding them.

The Pacific Flyway is a major north-south flyway for migratory birds in America, extending from Alaska to Patagonia. As part of the Pacific Flyway, California is a temporary home for many species of birds. Due to people feeding them, some of these birds no longer naturally migrate.

Adult roof rat
“Unfortunately, when we feed birds at parks with lakes and ponds, we are encouraging these unnatural situations and not helping the health of these bird populations,” Quinn said. “This can cause unnatural numbers of water fowl to congregate in ponds, rivers and lakes and creates perfect conditions for avian botulism and cholera to take hold. Bird die-offs can occur naturally in wilderness areas and are prominent in drought conditions due to low water resources.

Sustaining nonnative and feral animals can also have negative impacts on native wildlife, she said.

“For example, the eastern fox squirrel, which has now been released in many cities in the state, is competing with the native western gray squirrel,” said Quinn. “Sustaining the nonnative and invasive eastern fox squirrel could further aid in its distribution in the state, which would spell disaster for the native gray squirrel.”

Adult house mouse
Leaving nuts and seeds out for squirrels can also encourage other nonnative wildlife like roof rats and house mice.

“Not only do these species have public health issues associated with them, they also compete with native wildlife,” Quinn said. “They prey on bird eggs and can compete with native rodents for food resources.”

Indirect feeding of wildlife can also lead to serious conflicts between people and wildlife, Quinn warned.

“Bears that become accustomed to human food often have to be trapped and re-released and some are even euthanized,” Quinn said. “Coyotes are now common-place in some of our cities in California. Relying on human food could cause habituation of these wild animals and cause conflicts to rise. It is important that we cover our trash cans and make sure that we keep wildlife out of them.”

The California Department of Fish and Wildlife has an initiative called “Keep Me Wild” with the slogan “Wild animals don't need your handouts. They need your respect.” Quinn urges people to consider the long-term welfare of wildlife the next time they are tempted to feed wild animals.

For more information about managing pests around homes, visit the UC ANR Statewide Integrated Pest Management Program website:

Posted on Friday, October 30, 2015 at 11:01 AM

Roof Rats

When my friend Donna told me that roof rats were eating all her persimmons, I was incredulous. Roof rats?   And what a mess they made, too!  Eating half the fruit (the half you didn’t see), so that when you reached to pick it, your unsuspecting fingers sank into squishy soft, wet flesh, rather than the firm cool surface you had been expecting.   She eventually had her husband put out large snap traps for them, traps that resembled oversize baited mousetraps, and her problem ended for this season.

So it’s my turn now.  While cleaning up the windfalls under my unknown species apple tree (perhaps a variety of Red Delicious) I came upon what initially looked like edible windfalls which I collect and use,  and some lovely firm fruit still hanging.   But only half of the apple was there – the rest had been eaten on the tree.  Oh dear.  Roof rats…so that’s what my dog was barking at some nights ago.  She was actually trying to climb that apple tree.  At this point I’m reluctant to put out traps.  I may have to, but I’m hoping that my dog’s presence will deter future foraging.  We’ll see about that!

For more information about dealing with roof rats, see this link

Apple eaten by roof rat. (photo by Riva Flexer)


Posted on Tuesday, December 13, 2011 at 9:01 AM
Tags: eaten fruit (0), fruit (0), roof rats (0), traps (0)

OH, rats!

When I was a kid, I had a pet rat. The offspring of “Rat Olympics” medal winning parents, she was friendly and athletic. A smart rat, I trained her to perform several tricks. She was a domesticated rat and my pet. The wild rats that have been using our vegetable garden as their cafeteria, are pests.

Who's been eating my eggplant? (photo by Sharon Leos)

There are many public health issues associated with wild rodents and any pest problem is best dealt with early, before it gets out of control. The two most common rat species in California are the Norway rat (Rattus norvegicus) and the roof rat (R. rattus). Sanitation, rat proofing, and population control are the three main aspects of managing a rat problem.

The first sign of my rat problem was early in spring: vanishing bok choy (Brassica rapa chinensis). The outer leaves of the young leafy clusters were disappearing one by one over the course of a few nights. The amount of damage could not have been caused by insects and no evidence of slugs or snails was visible. Since they are active at night, I suspected rats. I constructed 24-inch tall cylinders of hardware cloth to protect the plants. After a few nights of experimenting with methods for securing the cylinders to the ground, the leaves remained undamaged. Hungry rats will find a way around obstacles, so I buried the hardware cloth about an inch deep and used garden staples to hold it in place. The bok choy was now rat proofed.

Adult Norway rat (photo by Jack Kelly Clark from UC Repository)
There are many methods of population control of rats. I feel badly about it, but let’s be honest, we are talking about killing rats. Using live traps is an option, but Norway and black rats are not native to California and releasing them in the wild could be harmful to the native plants and animals.

Things to consider when choosing a control method:

Rodent baits contain poisons that are also toxic to pets, wildlife, and humans. It may take several days for the poison to work allowing the rat (or mouse) the opportunity to find an inconvenient place to die like inside a wall or under a deck. The carcass may still contain active poison that could be harmful to cats, dogs, or wildlife that might consume it.

Glue or sticky traps are usually ineffective and rats can drag them around as they struggle to escape. Glue traps can be dangerous for wildlife such as birds and reptiles, and small mammals like kittens.

Trapping with a spring type trap is recommended by UC IPM as the most effective. It may be labor intensive, but it works. Over the summer, we controlled more than twenty rats in our garden. We religiously set the traps in the evening and unset any unused traps in the morning. Why not leave traps out all the time? Dogs, cats, and wild birds looking for food could be injured by the traps, and that is definitely not the intention.

For more information on managing rats, including trap setting strategies, visit the UC IPM website for Pest Note number 74106

Posted on Thursday, October 6, 2011 at 7:51 AM
Tags: eggplant (1), rats (3), rodent control (1), rodent damage (1), UC IPM (59)

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