Mole madness

Asked October 6, 2016, 7:37 PM EDT

What is an organic safe way to repel moles from your lawn and garden? Is there a way to spray for grubs?

Clackamas County Oregon moles

1 Response

The following references should help:
OSU Extension article "Crane fly--Are leatherjackets munching your lawn?"
Beneficial nematodes are applied when the soil is fairly warm, generally 55F degrees on labels for most you will find. The soil warms slower than the air does, so taking the actual temperature will be critical. I did not yet find an answer to how close the herbicide application can be to the nematodes application.
I will attach some information links about the nematodes. First, though, are you sure you have a white grub problem? They do not cause a problem every year on lawns in Oregon. The Multnomah Master Gardener Volunteers are available to help you identify your pest. Phone: 503-445-4608 Email:
The Lane County Extension Service has a clear information page about beneficial nematodes:
The Pacific Northwest Insect Management Handbook page about Turfgrass-White Grubs includes the pest description and crop damage typical in our area, as well as biological and home chemical control options.

You can identify moles and gophers by examining those dirt hills. However, you'll want to examine the very freshest mound - The mounds are formed when animals push loose dirt out of their underground tunnels, so when they quit pushing, some of the loose dirt starts to cave back into their tunnel. Gophers and moles push dirt out somewhat differently, so the slightly caved-in "plugs" show up in distinguishable places on the dirt mound. Gopher plugs will be to one side of a slightly fan-shaped dirt hill, whereas the plug in a mole hill will be right in the middle.

Because of the size of the area, exclusionary (below-ground) fences might be prohibitively expensive. If you have key areas within the yard you want to protect though, such as garden beds, fencing could still be an option. Over large areas however, lethal trapping or poisoning is the most common approach. Note that these two species have VERY different ways of making a living, which has implications for your choices of traps and/or poison baits. In either case, you'll want to be very careful to limit exposure of non-targets (e.g., pets, children) to these powerful traps and poisons, as well as to bodies of expired animals that have ingested poison.
All of the tunneling animals provide some neat ecosystem services such as soil aeration, water penetration, and nutrient mixing within soil. They also provide important food for many other medium-sized hunters ranging from terrestrial (such as fox) to aerial (such as hawks and owls). Moles are actually insectivores whose main interest in your yard centers on soil insects and worms! (However Oregon's largest-bodied mole species, the Thompson's, does require a broader diet to reach their energy requirements and so they can be guilty of eating below-ground plant parts such as roots and bulbs.)
For more info, see these dated but still useful brochures on
gophers -
& moles -
Please let me know if I can be of further assistance

This is one of 2 times during the year when moles are the most active - fall. The other is spring. At these 2 times of year, the soil is usually moist enough to tunnel through in search of food (earthworms, grubs, and other invertebrates). Perhaps the best method for dealing with mole damage is trapping. Here is a weblink for information on trapping moles:
A couple pointers - set the traps in the feeding tunnels (the tunnels that are just below the surface and sink in when you step on them). Do not place traps over or near the volcanic like mounds (these are excavations of deeper tunnels). To determine if a feeding tunnel is active, and a good place to set a trap, step on it to collapse it, then wait until the next day. If the tunnel is raised up again, you know its an active tunnel and is still being used by the mole.
Good luck - try to be patient and sometimes you may need to move traps around several times before actually catching any moles.