COLUMBIA, Mo. – Pest control is an important part of establishing an attractive garden. Insects, diseases and weeds are formidable foes, but the damage they inflict often pales compared to the destruction perpetrated by some of our four-legged “friends,” said University of Missouri Extension horticulturist David Trinklein.

“It is extremely frustrating to put time, effort and money into establishing an attractive garden only to have it decimated by deer, groundhogs and squirrels,” said Trinklein.

“Hunger is a tremendous incitement,” he said. “When food in the wild is sparse, wildlife will feed on garden plants. Additionally, once wildlife become used to feeding in the garden, it becomes difficult to prevent future depredation. Early intervention is important.”

Use IPM strategies for control

Trinklein suggests controlling wildlife damage with integrated pest management (IPM) strategies. Start with planting resistant species. Wildlife usually avoid plants that have pubescent or hispid leaves, pungent aromas or bitter tastes.

Here is a partial listing of popular ornamental plants that deer tend to avoid because of leaf texture, odor or taste: ageratum, asclepius, barronwort, bergenia, bleeding heart, canna, cleome, coral bells, columbine, daffodil, dahlia, gaillardia, geranium, hardy ferns, herbs, heliotrope, hyacinth, Japanese anemone, Japanese spurge, lamb’s ear, marigold, morning glory, nasturtium, nicotiana, ornamental onion, pansy, petunia, phlox, plumbago, salvia, Shasta daisy, Siberian squill, snapdragon, spotted deadnettle, statice, sunflower, sweet alyssum, sweet William, tickseed, verbena, vinca, yarrow and yucca.

Repel animals with noise

Devices or techniques that frighten wildlife can be effective deterrents when used properly. Examples include propane “scare cannons” and pyrotechnic devices such as noise bombs, screamer shells and firecrackers.

The results of their use are not permanent, and effectiveness depends on frequency of use as well as the ability of wildlife to become acclimated to the noise, Trinklein said. Consider variables such as timing and diversity of noise. For example, once in place, nuisance animals such as birds are less likely to respond to noise. Also, a variety of noises is more effective than a single noise used repeatedly.

Visual devices

Visual devices that frighten animals such as scarecrows, predatory bird figures, tin foil, pie plates and mirrors can be helpful. As with noise, these become less effective when animals become used to them. Relocate devices on a regular basis for best results, said Trinklein.

Chemical repellents

Chemical wildlife repellents usually are classified as gustatory (taste) or olfactory (odor). These repellents most often are sprayed (brushed) on vegetation and may contain a sticker of some sort to make them more rain-fast. Effectiveness depends on a number of factors, including motivation of the animal, habituation, concentration of the repellent, palatability of the plant being protected, rainfall and number of applications. “Suffice to say, the hungrier an animal is the less likely it will be deterred by a chemical repellent,” Trinklein said.

Homemade repellents

Trinklein suggests an easy homemade repellent that consists of a mixture of 20% whole eggs and 80% water by volume. “It reportedly is quite effective against deer,” he said. This mixture tends to withstand weather but should be reapplied monthly. Several newer wildlife repellents contain capsaicin, the chemical that imparts the “fire” to hot peppers.

When choosing chemical repellents, consider factors such as human (or pet) safety, toxicity to plants and expense.

Fences are most effective

Fencing, netting, cages and other methods that exclude wildlife from garden plants can be very effective in controlling damage, but they can be expensive. Using 36-inch chicken wire buried 6 inches in the soil is effective in controlling small animals such as rabbits or squirrels. A fence 8 feet high is considered to be an effective barrier for deer and wildlife other than birds. Woven wire (chain link) fences are most effective; synthetic netting (mesh) can be used but represents less of a physical barrier to highly motivated animals. Placing small cages of wire or netting over individual plants to deter wildlife can reduce expense but detracts from the aesthetic value of a garden.

“Electric fences represent somewhat of a compromise between initial expense and effectiveness in wildlife control,” Trinklein said. The number and spacing of fence wires depends on the species of wildlife to be controlled. For small animals such as rabbits, electrified wires located 2 and 4 inches above the soil surface should be sufficient.

For deer, a series of three wires located 18, 36 and 54 inches aboveground has proven to be effective, according to Trinklein. Baiting the fence by hanging strips of aluminum foal coated with peanut butter on the wires will help “educate” deer on the nature of electric fences and keep them from charging through on first encounter. In all cases, electric fences should be clearly labeled for safety purposes and monitored daily.