We all have our limits on what we will and won't tolerate when it comes to pests in the home and garden, but there are good reasons to control rodent populations, says Contra Costa Master Gardener Steve Griffin.

Rodents — rats, mice, moles, gophers, tree squirrels and ground squirrels — can cause damage to infrastructure and spread diseases.

Here are some of Griffin's tips on keeping them from becoming too much of a pest.

  • The first step is to identify what type of rodent problem you have. Knowing what animal is eating your plants, digging holes in your yard or snacking on food in the kitchen will determine what steps you take to control it.
  • Take a good look at your home and yard. Are you inviting the pests in by leaving pet food out, feeding the birds or having fruit trees?
  • Next, look at changes you can make to discourage rodents from visiting. You may need to start storing food in containers, removing food after pets have eaten, and pruning trees away from your home to prevent rodents from climbing onto your roof and into your attic.
  • Buttoning up entryways into your home also will help eliminate the problems inside, Griffin says. Outside, look at fencing and other exclusions.
  • If you decide to take lethal steps to control rodents, choose your tools carefully. Never use poisons, which often unintentionally kill other animals.
  • If you use traps that capture animals alive, you'll have to release them on your own property — it is against the law to relocate them without a permit from state officials, which is seldom given — or humanely kill the animals.

    Rats and mice

  • There are two species of rats — roof rats and Norway rats — that live with humans, and we have both in the Bay Area.
  • Norway rats usually are found on the ground floor. They have heavier bodies and tails that are shorter than the length of their bodies.
  • Norway rats prefer trash and wood piles, and basements.
  • Roof rats are great climbers and usually are found in the home, attic and garden. They are smaller than Norway rats and have a tail that is longer than their bodies.
  • Roof rats are agile climbers and nest above ground in trees, walls, cabinets and false ceilings.
  • Mouse populations rise and fall with the availability of food and weather conditions.
  • House mice are attracted to pet food, snacks left in drawers and pantries with plenty of food in cardboard or light plastic wrappings.
  • Mice will nest in walls, drawers and cabinets, and build nests of almost any materials the can find.
  • Rats and mice spread disease through fleas, feces and urine, which they leave behind on their searches for food.
  • Good housekeeping can keep most rat and mouse populations down. Repair door sweeps, plug entry holes, screen attic vents and the vents around building foundations. Trim limbs and landscaping away from the roof line and foundation walls. Pick up pet food and seal food in sturdy plastic or metal containers.
  • Trap mice and rats with snap or electronic traps. Do not use poisons.
  • Bait a rat trap with nuts or sticky candy tied to the trigger with twist-ties, wire or zip ties. Bait a mouse trap with peanut butter or a soft candy such as caramel.

    Gophers

  • Gophers live most of their lives underground, feeding on roots and tubers. They occasionally come out of their burrows at night to feed on plants, fruit and vegetables.
  • Gophers are not good climbers, so any vegetables that are low to the ground are targeted.
  • To know if you have a gopher, look for crescent shaped mounds of soil with a plugged hole. The tunnel radiates out from the crescent and angles down about a foot.
  • Gophers are solitary animals except for mating. Usually only one gopher will be found in a yard, and gophers will fight off other gophers for territory. Just because you see multiple mounds doesn't mean you have many gophers.
  • Owls are the best control for gophers, but not everyone has an owl nearby. You'll probably have to resort to exclusion and trapping.
  • Use a wire mesh under raised beds; bury the mesh — hardware cloth — 24 inches down to create a barrier around your yard or garden. Pair the underground fence with an above ground one.
  • If you choose to trap, practice setting it before you try placing it. There are many types of traps that are effective in killing gophers.
  • Choosing the right spot to trap is the key to success, Griffin says. Knock down all the old mounds and keep watch for a new one to appear. Dig out the mound and find the main tunnel below and leading away from the mound. Set two traps in the tunnel, facing each other, so the gopher will be trapped whether it is coming or going. Secure the trap and then place cardboard or plywood over the hole, covered lightly with soil. Wait a couple of days, then check the traps.

    Moles

  • Moles are insectivores and don't eat plant material. Any damage they do is to the appearance of your garden or yard, and occasionally they may kill a plant when they disturb the soil around plant roots.
  • Moles are difficult to capture and probably should just be left alone.
  • You can bury mesh, as you do with gophers, to exclude moles from the yard. Trapping rarely works.

    Meadow voles

  • This mouselike creatures hardly ever enter dwellings, but they can do some damage in the garden and landscape. Their populations rise and fall with great regularity.
  • Voles are active day and night, feeding on grasses, veggies, bulbs, roots and tree bark. Unchecked, they can girdle a young tree and kill it by eating the bark through the cambium layers.
  • Protect young trees with a guard at the base and keep ground covers away from the tree trunk.
  • Trap with unbaited mouse traps, placed in the pathways of the voles.

    Squirrels

  • Tree squirrels can be a nuisance, feeding on fruit and vegetables, and nesting in attics. They also can vector diseases through fleas.
  • Ground squirrels are extremely destructive, digging under roads, fences, foundations and utilities. They feed on vegetables and can destroy a garden in a short time.
  • Ground squirrels dig large dens with open holes. They also vector diseases through fleas.
  • Control ground squirrels with wire fences, above and below ground, and with an electric shock wire along the top of the fence.
  • Ground squirrels can be trapped and killed at any time; most tree squirrels are protected and can be taken only during hunting season, with a license. The Eastern fox squirrel can be taken at any time without special licenses.
  • Hawks, coyotes, foxes and bobcats feed on ground squirrels, so don't use poisons as a method of controlling the population.
  • Exclusion and deterrents are the best ways of handling any pest problems.

    Next time in the garden, knowing when to sow seeds or plant seedlings.

    Our Garden

    Our Garden offers free classes at 10 a.m. every Wednesday from April through October. Master Gardeners are available to answer questions and a large selection of seedling are available. All produce grown at the garden is donated to the Monument Crisis Center in Concord. The garden is at Wiget Lane and Shadelands Drive, Walnut Creek.

    Garden class schedule

    July 27: Knowing when to sow seeds or plant seedlings, Master Gardener Marian Woodard
    Aug. 3: Growing succulents, Ruth Bancroft Gardens curator Brian Kemble
    Aug. 6: Saturday workshop, Rethinking Your Lawn
    Aug. 10:Winter vegetable gardening, Master Gardener Janet Miller
    Aug. 17: Fermenting and preserving, Master Gardener Susan Mossbacher
    Aug. 24: What went wrong in my vegetable garden, Master Gardener Terri Lippert
    Aug. 31: Compost tea, Placer County Master Gardener Kevin Mariani
    Sept. 3: Closed for the holiday
    Sept. 7: Creating harmony in the garden, Garden Coach Patrice Hanlon
    Sept. 10: Dry plant sale
    Sept. 14: Building healthy soil with Master Gardener Steve Andrews
    Sept. 21: Gardening the heugelkulture way
    Sept. 28: Creating rain gardens, Master Gardener Roxy Wolosenko
    Oct. 1: Saturday workshop, Creating Wildlife Habitat
    Oct. 5: Growing cover crops, Master Gardener Janet Miller
    Oct. 12: Growing citrus and avocados, Ed Laivo of Four Winds Nursery
    Oct. 19: Growing roses from seed, horticulturist Kathy Echols
    Oct. 26: Fall and winter care of fruit trees, Janet Caprile UC Cooperative Extension farm advisor