Gophers: All Or Nothing
August 1, 2010 
Editor’s Note: At a lot of conferences, trade shows, and meetings over this past winter, we heard complaints about gophers. Pocket gophers can be an insidious problem, because while they can do obvious damage to young trees or vines, in mature orchards and vineyards they fly under the radar. There might be some decrease in yields, and perhaps some nibbling on buried drip lines, but it all adds up. To find out what growers can do to protect their plantings, we caught up with Roger Baldwin, the University of California Cooperative Extension IPM Wildlife Pest Management Advisor at the Kearney Ag Center. (Some of his answers are slightly edited for length and clarity.)
Baldwin: I would say stay on top of it. When you decide to get after them, get after them. When you get their populations down low, keep them low. It might cost you a lot that first year, but after that costs will be much lower. Also, if you go with traps, your material costs are mainly just that first year. Keep in mind, it doesn’t do a lot of good to reduce gopher populations by 30% to 40%; they will just re-infest through reproduction and immigration. Realistically, you should shoot for a minimum reduction of 70% and preferably closer to 90% to have a real long-term impact.
Also, don’t be afraid of thinking outside the box. I don’t mean taking an illegal approach. But consider using a couple different methods at the same time. If trapping is not working in one part of the orchard, come back with fumigation. Ask yourself some questions. Why isn’t a given approach working? Am I not doing it correctly? Or is it the method? If a given approach isn’t working, don’t just keep doing it that same way.
A/WFG: What’s the most common mistake you see growers make?
Baldwin: Either deciding that populations are too small, or they’re not reducing the populations enough. Or implementing some form of control and then not monitoring the results. You really need to stay on top of gophers and keep populations low. With gophers, one or two is too many. That will lead to more gophers, and they are inherently difficult to control because they live below ground. Controlling gophers — once populations get large — takes a lot of time, effort, and money.
A/WFG: After you get control, if your property borders wildlands, can you expect gophers to re-invade soon?
Baldwin: Yes, generally by the next year. You’re in a situation where it will be more difficult for you. If you get rid of 95%, then constantly control the perimeter, you can reduce re-invasion rates. There is some hope. But if you’re adjacent to wildland areas or if your neighbors don’t make much of an effort, you are always going to see gophers. Talk to your neighbors. If you can get all your neighbors on board, your life will be a lot easier.
A/WFG: Is there a way to help slow re-invasion?
Baldwin: If you’re going to replant and you have an extensive gopher population, go through with a deep ripper to destroy the burrows and some of the existing gophers. Having an extensive burrow system will increase re-invasion rates, and the best way to slow re-invasion is to destroy the burrow system by deep-ripping.
A/WFG: Any final word of advice a grower may not have considered?
Baldwin: If you have a very serious problem in an old and mature vineyard or orchard, it may be more cost-effective to let it be if you’ll be replanting anyway in a year or two and you plan to deep-rip before replanting to destroy the burrows. If you’re going to use aluminum phosphide (fumigant) to control the gophers, do that before you deep rip because fumigation isn’t as effective immediately after deep ripping. If you’re going to trap, trap a couple of weeks after deep ripping as deep ripping will remove some of the gophers for you which will result in less trapping on the back end. Remember, deep ripping will kill some gophers, but by far the main benefit is the destruction of the burrows.
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