It’s been a long time since I have reviewed gopher control in the vineyard. It’s appropriate, given the time of year, so I thought we would take a look at it this month.
Gopher control can be approached very specifically. If you review back issues of Wines & Vines you’ll find that I wrote a three-part article covering every aspect of gopher control, in 1997. For our purposes here were going to lump gophers, ground squirrels and meadow mice or voles into one big problem rodent category.
All three rodents damage grapes by chewing on them. New plantings and established vines are susceptible to both root damage and girdling. In addition to plant damage, these rodents will also move enough dirt to redirect water away from vines and literally into a hole in the ground. Ground squirrels specifically will chew drip lines and damage emitters. I have observed squirrels chewing things for no other reason than the fact that they are there.
Control of these pests is broken into three fairly broad categories: biological, chemical and trapping.
Biological control includes habitat management and the encouragement of predators to inhabit the vineyard. Habitat management is weed control. If you have a good weed control program you will have fewer places for rodents to hide and feed unnoticed. In addition, flood irrigation may be used to discourage rodent populations from becoming established
Barn Owls and hawks make up the other side of the biological control equation. There are a number of Barn Owl nest boxes and raptor perches available to the grape grower and all have their place. Raptors will not solve any rodent problem. However, they do eat them and can’t hurt “the cause” any. In addition, any time you can encourage biological control, I say do it. If nothing else, it’s fun to watch and you are creating and promoting habitat and wildlife, which is usually a good thing.
Chemical control is the next broad category to cover. Most grape growers have the following chemicals available: Diphacinone, an anticoagulant that is a chronic toxicant, Strychnine, an acute toxicant, Aluminum Phosphide, a fumigant, Zinc Phosphide, an acute toxicant and smoke cartridges.
Ground squirrels can be baited with Diphacinone treated baits in bait stations or scatter baited with oats treated with Diphacinone. Gophers can be treated below ground with Strychnine treated milo, Diphacinone treated baits or Zinc Phosphide.
Both ground squirrels and gophers can be controlled with smoke cartridges or Aluminum Phosphide. The latter is a restricted use product that not everyone has access to. Which brings up an interesting topic.
Most of these products are available in different formulations. The less toxic formulations are available to the general public and the more toxic (readeffective) formulations are only available to licensed applicators after a recommendation has been made by a pest control advisor (PCA).
It is usually worth the time and money to have a professional come out and begin a rodent control program for you. You don’t have to stick with them forever, but you can learn a lot from them and all of it will benefit the vineyard. The most common mistake made in a rodent control program is looking for results too quickly. Ground squirrels, gophers and meadow mice live under ground. A glance or even a walk through the vineyard does not easily measure their activity level or population fluctuations. Time, effort and patience are rewarded with fewer holes in the ground and less damage to vines.
Trapping is the final category to review. We have been greatly limited to what traps we can use for rodents. Unfortunately, misinformation and “biological management by emotion” have removed some of the effective traps that had been used by pest management professionals and growers for years. However, it is still possible to trap gophers under ground with lethal body gripping traps. This method is time consuming but effective for one or two problem gophers and should be limited to an ornamental situation rather than a vineyard application. Ground squirrels can be live trapped in cages, but what’s the point? This method is also too time consuming to be considered effective.
I realize how broad this category is, and how general I have been in the article but at least it gives you an overview of rodent control methods available and what works. Bear in mind that I have included everything that does work. I have left out such time wasters as inserting chewing gum in gopher holes, using mothballs (What is it about mothballs? They are the “tastes like chicken” catch all of old school remedies for everything) or using ultrasonics for vineyard gopher control. If you have something that you’re curious about or don’t feel like I gave you enough information, feel free to give me a call (559-490-2262) and I’ll try to give an intelligent answer. Until next time, good luck with those rodents.