Gopher Peeking
This photo of a Botta's pocket gopher was taken by Stephen Shankland at Point Reyes, California. Thanks, Stephen!

“We’re Playing for Keeps Now”

Gopher Wars Part II

The idea of Integrated Pest Management (IPM) is that you approach a pest problem with a series of steps so that the solution to your problem causes the least harm to the environment. Think of it as the gradual escalation of hostilities. They say there are six steps:

  • Proper identification
  • Learn the pest and host life cycle and biology
  • Monitor activity
  • Establish an action threshold: how much damage is tolerable?
  • Choose a combination of management tactics: Cultural, Biological, Mechanical and Chemical Controls
  • Evaluate results

Identify and Learn

Depending on your source, they will express the steps of IPM differently but this just about covers it. The first two may seem obvious but not so much. Consider this:

Every spring, this bug shows up on one of my plants. It eats like crazy and if you find one, you’ll find a dozen. You can actually watch the little monster grow before your eyes until it is huge and fat on all the leaves it has eaten, leaving the plant looking all raggedy. Then the bug disappears for a while until the cycle starts again, over and over through the whole growing season. What would you do?

The Monarch Caterpillar on my Milkweed (Asclepias physocarpa)
The Monarch Caterpillar on my Milkweed (Asclepias physocarpa)

Think again. That’s the monarch caterpillar chowing down on my milkweed. Last year was the first time we planted milkweed and I totally freaked out one morning when I found about 18 fat caterpillars on two plants. The caterpillars pretty much stripped the young plants but – guess what – milkweed doesn’t seem to mind. It regenerates so quickly that there is no real loss.

Not all critters are pests and not all pests are intolerable.

But let us get back to gophers. It is easy enough to identify the critter even if you don’t see them. We were seeing “feed holes” and mounds of freshly dug dirt. A gopher’s feed holes are usually just large enough for a gopher to pop up from its run and eat the plant material right around the hole. Gophers’ mounds are crescent shaped around a plug.

Gophers' Feed Holes
Gophers' Feed Holes

The damage to plants is also an indicator of gophers. They will eat the roots below ground and the plant above ground will die. Gophers will also start with the roots and then pull the rest of the plant into their burrows. A friend was telling me that his wife heard a noise in the garden and turned just in time to see a plant descend into the ground. Gophers!

Monitor and Establish an Action Threshold

Beneficials and other biological controls are the reason the next step is “Monitor.” We have a new tree that is being plagued by aphids. Rosalio, the man who helps us ’round the yard, wanted to spray it immediately with an insecticide. I favored blasting the leaves with a hose to wash off the aphids. Even as we were debating this, we saw a ladybug land on a branch near our heads. Since natural predators were starting to gather, we decided to do nothing. Since then, the damaged leaves have been replaced by new growth and the aphid population is in decline. Sometimes, the wait-and-see approach is all you have to do.

I gotta tell you, though, monitoring gopher activity is a problem for me. Though an established plant might be able to tolerate some damage to an extensive root system, young perennials and annuals don’t have that advantage. Even young trees can be felled by gophers when they girdle the trunk. Gophers have tremendous power in their jaws so they can also chew through below-ground irrigation and electrical lines. Their tunnels can undermine a slope and accelerate erosion. They can even destabilize the foundation of a building.

For years, our backyard was part grass and part dog run. Though there was some gopher activity, we didn’t have much in the way of ornamentals to protect. Our gopher control efforts were irregular and ineffectual but we didn’t have much to lose. When the last of our dogs lived out her life, we decided to take back the backyard. With dozens of new plants and more going in all the time, we have a lot to lose.

Now, we have zero tolerance for gophers. Spend a little time monitoring them, and you may lose significant plant material and have other damage. My advice is don’t wait.

Management Tactic: Cultural Control

I think of Cultural Control as your good gardening practices. It has to do with the plants you choose, the design of your garden, and your maintenance practices. One of the good examples of plant selection is selecting resistant varieties of tomatoes if you have nematodes in your soil. The design of your garden might include companion plant practices – combining plants that help each other. French Marigolds are often touted as an antidote to nematodes. Basil is said to improve the flavor of tomatoes while repelling some pests. Other design considerations are the cultural requirements of groups: plants with like needs of light, nourishment, and water will grow better in a bed designed to meet those needs. For example, over-watering one plant while under-watering another will put both at risk. Maintenance practices includes proper watering, feeding, and tending so that your plants are not stressed and more susceptible to pest but also sanitation, meaning keeping your garden clean of debris that might be harboring pests. Litter in a garden is a great place for snails, slugs, and earwigs to hide.

But how does this work with gophers?

Plant selection is a tricky one. I want to dispel a myth: gopher spurge doesn’t work. I have heard variously that the smell of the plant or its poisonous parts take care of gophers but numerous scientific studies don’t support that idea. In Gopher Alley, we planted Angel Trumpets (Brugmansia) and they have been totally unaffected by the gophers. Our best guess is that the gophers sensed or learned that the roots are toxic and just went around the plants to other, tastier selections.

If you are just starting a vegetable garden and installing your beds, you can take some preventative measures as part of your construction. In raised beds, line the bottom with hardware cloth. I was talking to a gardener who had just built raised beds because of his gopher problem but he lined the bottom with chicken wire. That is almost no barrier at all for a gopher. The wire is thin and with just a couple of breaks – either when it rusts out or if the gopher chews on it – it’s like an open door. I have heard of something called Gopher Wire that is similar to chicken wire in appearance but thicker and galvanized. Perhaps that would counter my objections but I have never seen it myself. I use hardware cloth, available at any hardware store.

Besides lining raised beds, you can also line planting holes. This usually works best with larger plants but it isn’t infallible. We planted two magnolia trees in Gopher Alley three years ago and both have been struggling ever since because gophers managed to get by the barrier. It has worked for other plants, though, so it is worth the effort when it works.

Cans of Gourds
Cans of Gourds

We also adapted a planting tip we heard two years ago when we lost several bougainvillea in Gopher Alley: cut out the bottom of the pot and plant bougainvillea in the original nursery container without disturbing sensitive roots. Ah ha! We realized that this might also give the plants just enough protection from the gophers. Our bougainvillea are now huge and lush.

This year, I am planting gourds along the fence in Gopher Alley and any damage to their root system would be intolerable. I decided to plant the vines in large food cans with lots of drain holes and then plant the cans along the fence. So far, it seems to be working.

We can’t create a gopher proof barrier in our vegetable garden because it is 12 by 20 feet and raised only about eight inches. It is more like an in-ground bed that we raised slightly to improve drainage and to create a level, defined planting area. Last year, when we put in this bed, gopher activity was minimal. Retrofitting it with hardware cloth now would mean excavating the whole site and that’s just not practical. Another gardener told me that she, frustrated by the gopher attacks on her in-ground beds, grew her vegetables in nothing but EarthBoxes® set in the old in-ground garden. It became, in effect, a container garden.

You can install some kind of fencing or other barrier in a trench two feet deep in the soil to keep the gophers out. Rosalio, who grew up in an agricultural community, said that when they were preparing a field, they dug a trench around it and fill it with horse manure. Apparently, gophers don’t “like” digging through manure. Someone else told me about a similar method used but the trench was filled with very soft soil so that burrows would collapse. Frank is against anything that involved digging a trench that deep through Gopher Alley and I can’t take on a major project like that without marital accord.

There is a school of thought that you can repel gophers with the noise from whirly birds (those spinning plastic flowers) or battery-operated sound probes stuck in the ground. We have tried both but neither worked. A vertebrate expert told me that if the sound produced by either startled the gopher at first, they would quickly become accustomed to it. This reminds me of car alarms: the first time you hear one, you react with concern; eventually, if you react at all, you wonder why that idiot doesn’t turn the darn thing off.

Sometimes everything you do to prevent an invasion doesn’t work. So what’s next? Stay tuned for Gopher Wars III: Au Revoir, Gopher.

by Zone 9 Deputy Gardener Laurie Gore

Reader Comments

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Terry

It is uncertain what the myth is-Gopher spurge works or doesn’t! Only by reading through the off topic stuff of the blog does one come across the statement that in fact it doesn’t work. Could be clearer!

Reply
Laurie Gore, Zone 9

That's a really good question and I thank you for asking it. The USDA hardiness zones are good for determining the length and timing of winter cold in an area but not much else. My growing conditions here in Bonita because of my own property's micro climate are similar to conditions further inland and Zone 9. We are in the eastern-most tip of the zip code on a south facing slope. I have a friend in the west side of Bonita with a north facing slope and his growing conditions are quite different.

In my opinion, there are better ways of determining a growing zone than the USDA system. Out west, we use the Sunset zones to talk about gardening. The American Horticultural Society has developed its own system and you can read about it at http://www.ahs.org/publications/heat_zone_map.htm. I think there are another couple of the Heirloom Gardeners who also found that the USDA map was a little off for their particular situation.

I'm working on a piece right now about Resources — where to do learn what you need to know about gardening — but no one source has it right all the time for you in particular in your own garden.

Reply
Shirley Hay

I'm confused. You are called the zone 9 gardener. I'm going by the National Gardening Association USDA Hardiness Zone finder by zip code. For Bonita it (91908/02) it says 8B. I live In Tucson (85749) it says 8A. Am I mixing apples & oranges?

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Laurie Gore, Zone 9

How true! There are those unexpected successes. One day, while mowing, Frank saw a gopher pop up out of a feed hole right in front of his mower. I can't recommend this as part of an IPM plan but you go with what works…

Reply
Marcy Baugh

The only way the whirligigs drive away gophers is if you happen to hit the gopher on the head with it when you drive it into the ground.

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