Vertebrate pest controls
Vertebrate pests present challenges unlike any other landscape pests. Several issues affect control decisions, some with little direct bearing on the practical side of control strategies. In other words, the most effective control might not be the most prudent to choose.
Not only do wildlife regulations come into play, but so does public sentiment driven by some people's attachment to animals. Additionally, some measures, such as shooting and certain methods of poison baiting, are simply too risky to conduct in urban settings.
For these reasons, live traps, repellents and feeding deterrents are more acceptable, if sometimes less effective, alternatives for landscape settings, with certain exceptions.
When we speak of "vertebrates," we're referring to a diverse group of creatures. However, most vertebrate pest problems can be attributed to three groups: deer, birds and rodents.
* Deer. In urban settings, public sentiment as well as safety considerations limit the feasibility of hunting or using any other lethal method as a control measure. Your options at many sites may consist of little more than deciding which deterrent to use, and perhaps erecting protective cages around young trees.
Deer repellents have their limitations. If deer are numerous or hungry enough, they sometimes will feed even on treated plants. Nevertheless, repellents often are effective enough to prevent serious damage to treated plants.
Anecdotes about homemade and unconventional repellents abound. Human hair, soap, rotten eggs, blood meal and many other substances all are claimed to repel deer. Research shows that many of these materials have some degree of repellency, but the effects are often inconsistent or too weak to prevent significant damage.
Deer prefer some plants to others, so it makes sense to select plants known to be less desirable to deer. Check with your local cooperative extension or wildlife control agency for lists of deer-resistant plants.
* Birds. Without a doubt, Canada geese are the No. 1 bird problem for most grounds and golf courses.
Even though in-season hunting is allowed in many states, regulations otherwise prohibit harming Canada geese. Thus, as with deer, control measures basically consist of ways to make them leave or applying some substance to make turf unpalatable.
Tall vegetation at the edge of ponds often is effective in deterring geese, which prefer visibility and open flight paths into and out of water. Livestock dogs trained to harass geese are becoming more popular and can be quite effective at driving them off.
Methyl anthranilate, a harmless substance derived from grapes, is the most widely used feeding deterrent. Anthraquinone is another distasteful ingredient used in deterrents.
* Rodents. This group, collectively, creates the greatest number of problems for grounds managers.Rabbits, tree and ground squirrels, gophers, moles, voles and more occasional pests such as beavers inflict serious damage. The destruction may result from tunneling or digging holes or from direct feeding on ornamentals. Rats and mice also are of concern from the standpoint of public health.
* Trapping. This may be the most common method of controlling rodents in landscapes. Both live and lethal traps are used. Before attempting controls, you should check with a local or state wildlife agency about wildlife regulations that may prohibit harming rabbits and squirrels.
Live traps are simple and effective, but you must then transport a captured animal to a distant location to prevent its return. This is a burdensome task if you are dealing with many animals.
Lethal traps come in a variety of configurations. They are regarded as the most consistently effective method of controlling moles.
* Repellents. A range of repellent products is available for rodent pests. Capsaicin, a common ingredient derived from peppers (it's what makes peppers hot), is almost universally distasteful to herbivores. Thiram repels rodents in addition to deer, and castor oil is the most frequently used mole repellent.
Unconventional repellents abound, ranging from chewing gum to mole-repelling plants to ultrasonic waves. Though some of these products make bold marketing claims, many are untested or have not performed well in independent research.
* Poison baits. Poison rodent baits are not used as frequently in landscapes as in agricultural settings. There are, however, some situations in which a grounds manager may need them. Al Smith, national sales and marketing manager for rodenticide manufacturer LiphaTech Inc., explains that rats can become a problem at country clubs and similar facilities where kitchens discard their waste in outdoor dumpsters. Norway rats often take up residence nearby, and baiting can be an effective control in these instances.
According to Smith, another species found in coastal areas, the roof rat, nests in trees and especially seems to favor taking up residence in palm trees. Again, poison baits are appropriate for this situation.
Some active ingredients have been around for decades and still are used widely. For example, Smith notes that strychnine is still a popular product for field rodents such as pocket gophers. Warfarin is still available as well, but some rats and mice are showing resistance to it.
Other available actives include chlorophacinone, diphacinone, zinc phosphide and bromethalin, and the relatively new chemicals difethialone, bromadiolone and brodifacoum. Most products that use these actives have labeling for Norway and roof rats, and some for pocket gophers as well.
You should take all necessary precautions to prevent access by children and non-target animals to poison baits. Using an appropriate bait station should accomplish this.
* Smoke bombs. "Bombs" that you light, insert into burrows and then cover with soil are a traditional method of controlling ground squirrels and gophers. Their effectiveness depends on adequate soil moisture to prevent the smoke from dissipating out of the burrows. Gopher tunnels often have several entrances and it may be difficult to find and cover them all to contain the smoke.
* Cultural and physical controls. Don't overlook other possible steps to alleviate negative effects of wildlife. For example, rabbits' most destructive habit is girdling stems of woody plants. Simple trunk guards can reduce this type of damage. Moles, which tunnel in search of food, may be prompted to look elsewhere if you reduce grub populations.
The table below lists some of the available chemical controls for birds, deer and rodents. Remember that most of the products listed are EPA-registered pesticides, which means you must follow all label instructions. Also check with local officials about regulations governing wildlife-certain control methods may be prohibited in your area.
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