With their large size, conspicuous habits, and distinctive tracks and scat, white-tailed deer are probably the easiest animals to pinpoint as a potential threat to plant growth. Indeed, you can often witness the actual offense taking place when the culprit is a deer. But unlike birds and small mammals, which tend to inflict most of their damage around the farmyard itself, deer pose a more widespread problem because they also feed on crops (particularly corn) and trees (such as in orchards) in the far reaches of the property.
Damage and losses caused by white-tailed deer in Iowa
- Consume corn and soybeans in agricultural fields, causing economic losses.
- Eat leaves and twigs of trees and shrubs in yards, orchards, and tree farms, sometimes causing permanent disfigurement or death of plants.
- Enter yards and consume landscape and garden plants.
- Eat stored feed intended for livestock.
- Collide with automobiles on roadways, leading to vehicle damage and injury or death of motorists.
- Stunt forest regeneration by over-browsing seedlings of oaks, hickories and other trees.
Identifying deer damage
Whether in a distant corn field or a row of fruit trees along your garden, deer damage can be directly identified by the jagged (uneven) marks they leave after tearing off the growing portions of plants. These signs differ considerably from the more sharply defined cuttings left by rabbits and some other small mammals, which have both upper and lower front teeth that enable them to cleanly snip vegetation. Deer can exploit just about any type of plant on your property but their greatest impact is more prominent along edges where they spend most of their time.
Deer, like all herbivores, prefer actively growing portions of plants, like shoots, buds, and sprouts. On growing corn, deer target the newest, greenest growth from when the corn is just a few inches tall all the way to the end of the growing season. They become even more determined when the corn reaches about 2.5 feet in height, which is a very comfortable eating height for both bucks and female deer. This habit of feeding higher on the plant helps distinguish deer from other animals that knock corn over or eat lower on the plant. Deer continue to target the newest shoots on the stems at this height, often leaving the horizontal leaves intact. Weeks later, the deer shift to pulling freshly emerged kernels from the cobs, which can in turn lead to obvious stunting and infection of the cob for the remainder of the season. When the corn becomes more fully developed, deer will chew off big chunks from healthy cobs that escaped earlier attacks. Although deer feed on different portions of the plant in different ways across the year, the damage remains distinctive and easy to separate from other cropland intruders, like raccoons or beavers.
Managing the negative impacts of white-tailed deer
White-tailed deer are a popular game species in Iowa, and consistent harvest of adult female deer can be an effective way to control their population and thus their impacts on farms and forests. Landowners can help maintain the balance of local deer populations by taking advantage of established seasons to allow hunters to legally harvest deer from their property. This is especially relevant for landowners who live in areas with high deer densities, like heavily forested areas or areas adjacent to refuges like cities. Special harvest seasons and tags are available to landowners who have high economic losses to deer that cannot be controlled through regular hunting seasons. Contact a Wildlife Depredation Biologist from the Iowa Department of Natural Resources for more information on those tags and other services this program provides to address deer damage.
The surest way to prevent deer damage issues is to exclude them from crops or landscapes where they may do harm. There are several options for keeping deer our of the areas where they cause damage.
Small-scale exclosures. In the farmyard or similar settings, an effective, targeted approach is to place woven-wire cylinders around young trees and shrubs (and around the trunks of larger trees) to prevent deer from browsing on the twigs and fruit or damaging the trunk with their antlers. This widely used, cost-effective method also helps to keep pesky rabbits off of these plants. Modern snow fencing, which is comparatively inexpensive and simple to install, can also be used in the same way to exclude deer and rabbits from single or multiple plants, such as clusters of shrubs or fruit trees.
Fences. The most effective means of reducing deer damage on broader portions of your property is by constructing fences around vulnerable areas, such as crop fields, larger vegetable gardens, and orchards that span multiple acres. Fencing can be expensive and highly labor intensive, but will eliminate deer problems if constructed and maintained appropriately. The first line of defense selected by many landowners involves the installation of passive exclusion fencing that does not involve any sort of electrical charge as a deterrent. The design can vary somewhat depending on the terrain, but some tried-and-true specifications help to keep deer from going under, over, or through any openings. Regardless of the setting, a passive-exclusion fence must be at least 8 feet in height to prevent deer from leaping over them – and provide a barrier all the way to the ground to keep deer from ducking beneath. To accommodate these upper and lower barriers, you can install tall (16-foot) poles – anchored 4-6 feet into the ground – and space them at intervals of about 40 feet. String multiple strands of high-tensile wire or tall welded-wire fencing between the poles.
Active-exclusion fences use electricity to keep deer from entering. When deciding what type of active-exclusion fence to use, consider whether deer need to be excluded year round or just seasonally and how large the area of exclusion needs to be.
Temporary electric fencing can be less expensive and easier to install than permanent fences. Research has shown that products using synthetic rope or ribbon with conductive wires running through can be highly effective for reducing deer damage. These types of fences are generally only useful for areas smaller than 40 acres but they can be put up and taken down fairly easily if they are only needed at certain times of the year. Short electric fences can be effective in discouraging deer from entering small patches or gardens, but need to be tall or angled to prevent entry into larger (more than 100 square feet) patches. The number of strands necessary to deter deer can vary depending on how motivated the deer in the area were. Applying thinned peanut butter to synthetic fence at deer nose height can increase effectiveness, as deer will learn quickly that the fence is electrified.
Permanent electric fencing is more costly and can be labor intensive but methods for installing them are becoming less difficult. High-tensile electric fences seem to be the most effective permanent electric fencing option. Three different set-ups are often used: 5 foot vertical 5 strand, 5 foot 6-7 strand slanted, and 3.5 ft offset or double fence. Research has shown that the 5 foot vertical 5 strand fence is often most effective.
Note: The effectiveness of any fence will vary greatly in different settings. Adjusting the height and number of strands on temporary fences can be useful based on the level of deer pressure in your area. Additionally, research has shown that removing a few deer that habitually get through a fence can often be effective.
For more information check out the Iowa DNR Wildlife Damage Management page. There you can find an article on identifying crop damage, abatement techniques to deal with damage, and information on options available to producers with deer damage. Nebraska also has a useful publication on deer damage management.
This article is an update of "Managing Iowa Wildlife: White-tailed deer" (PM-1302g) originally authored by Lynne Fischer, William Clark, and James Pease.