Managing Vertebrate Pests

 
  Hort Snacks - November 2016
Download 930K pdf file ("HortSnacks-Nov2016-reduced.pdf")PDF
(930K)
     Subscribe to our free E-Newsletter, "Agri-News" (formerly RTW This Week)Agri-News
This Week
     Hort Snacks HomeHort Snacks Home
 
 
 
 Basic Life Requirements | Deer & Similar Pests | Deer Factoids | Rodents | Roden Factoids | Birds | Rabbits & Hares | Rabbit Factoids | Humans | Other Relevant Resources | Pest Control Suppliers

Vertebrate pests are bigger than your average insect and are simply animals that have skeletons and can include things like birds, deer, moose, elk, rodents, and other 2 or 4-legged animals (including humans). Whereas insect pests and diseases reduce the size and quality of your harvested crop and can reduce vigour and plant health, vertebrates typically directly affect plant survival, in addition to reducing yields. When growing perennial crops, this means interrupting the growth of a long-term crop and in many cases, requiring replanting and starting over. This also happens for many annual crops.

When it comes to vertebrate pests, you can’t really take the same approaches to management as you might with diseases or insects. Vertebrates are a large, visible part of the food chain, and poisoning (which is essentially when we are doing with insecticides and fungicides) on an entire orchard or field scale can have huge impacts on the entire chain (some might argue the same things for pesticide use for insects and diseases, but that is for another time). My point is that you can’t just spray an entire orchard or field to control a vertebrate pest, for a number of reasons. First, these pests don’t typically live or stay in the area all the time and as with any pesticide, you need to get the product in contact with the target. Second, they are larger and require a lot more to kill them. Third, poisons can concentrate within the food chain and non-target organisms will inadvertently be harmed. Fourth, widespread application of chemical can harm non-target organisms. The list can go on.

So how do you manage these pests? The answer is multi-faceted (and complex). The first step is to understand the habits and life cycles of the target pest so as to find where you can reduce the damage with the least amount of impact on other non-target organisms. Then you can use a range of techniques to accomplish your goals.

Basic Life Requirements

Essentially all vertebrate pests have some basic requirements in order for them to thrive. They all require food, shelter and minimum exposure to predators or other threats. Depending on the size of the animal, this can mean that longer grass, wild and rough or wooded areas, coverings, or buildings, etc. can meet the shelter/protective requirements. Food may be supplied by your crops, depending on the season and the availability of other food sources. Access to your crop is all they need.

The key techniques to managing most of these pests include exclusion (keeping them out), exposure (removing their protection) and removal (death or relocation). Within these general themes, practices may include sanitation, use of repellents / deterrents, hunting / trapping, poisoning, etc.

Deer and other similar pests

Deer, moose, elk, etc. can cause a lot of damage to all sorts of crops, whether orchard crops or newly emerging annual vegetable crops. They are typically present in all areas and during all seasons, although they may make their presence known more in certain seasons. They feed on plants, shoots, branches, and leaves and may also cause mechanical damage when they move through crops (i.e. broken branches) or when they forage for food (e.g. damaged mulch, dug up crowns, etc).

One of the most common ways of managing these types of pests is by allowing seasonal hunting on your property. This will not remove a problem but may reduce the population to levels that have less economic impact for your farm. When looking at this option, consider the regulations that accompany this (including both allowing and disallowing hunting). Check with your local Fish and Wildlife Officer for details.

Perhaps the most effective management practice for this crop is to put up fences. If the area where your crops are located is fenced properly, and those fences are maintained, you should be able to keep the problem out. Fences are expensive, there is no question. But if the difference between having a crop and not having a crop is the cost of a fence, then perhaps the choice you have to make is easier or clearer.

When fencing property, it is easier to start with the animals outside of the area, rather than remove them later. Fence early, rather than later. Keep future expansion and development in mind when planning a fencing project. Maybe fence a larger area than you have planted now.

When putting up your fences, consider the predominant species for your area. Bigger animals like moose or elk will require a stronger fence, while smaller deer can jump quite high, so height might be more important. Consult a fencing company or a Fish & Wildlife Officer for assistance in designing a suitable fence.

The use of deterrents or repellents is common. Unfortunately, the level of success is pretty varied and is almost never the same from one place to the next. Deterrents are things like bags of hair, bars of soap, etc. Their main feature is scent, which turns off the animal and encourages it to go elsewhere. There are also commercial repellents, which either have a bad taste or odour. It is important remember to keep them fresh and varied.

Everyone can adjust to something, even pests (perhaps I should say, especially pests).

Deer / Elk / Moose Factoids

  • Ungulates = two-toed
  • This group is native to all continents except Australia and Antarctica
  • Top Speed
  • White-tailed deer = 30 mph / 48 kph
  • Moose = 35 mph / 56 kph (sprint); 20 mph / 32 kph (trot)
  • Group Names
  • Deer / Moose = herds
  • Elk = gangs
  • White-tailed deer can leap 10 feet (3m) high and 30 feet (9m) in a single bound
  • Moose are great swimmers and can submerge completely for 30 seconds or more
Deer Factsheets
Deer Control Options

Various examples of electric deer fencing and bait
Photos by Robert Spencer

Rodents

Rodents can be a big problem for producers of a wide range of crops (especially tree and shrub crops). Besides the incredible reproductive potential of some of these pests, they can be very destructive and quite literally lurk around, under and within your fields, crops, storages and the other areas on your farm.

Rodents include animals such as voles (which are commonly called mice), mice, rats (NOT IN ALBERTA!?), moles, gophers, ground squirrels, porcupines, beavers, etc. It is a pretty confusing group when it comes to names, as most of what we commonly refer to as one this, is actually something else (confused yet?).

Rodents damage crops and plants by feeding on seeds, chewing off bark, shoots and roots (girdling) and occasionally root pruning. Some rodents also contaminate produce in storage with their urine and feces.
Porcupines, while less prolific than things like voles, can cause problems for producers. They can be managed either by shooting, trapping and removal or by using repellents or mechanical barriers. It is illegal to poison porcupines in Alberta.


Correctly positioned mole trap in Saskatoon berry orchard
Photo by Robert Spencer

Management of some of the other, smaller, rodent pests can be accomplished in different ways. Exclusion can be difficult for the smaller pests, but ensuring building and structures are well maintained can help to keep them out. For the larger ones (such as beavers or porcupines), tree wraps or wire may protect the lower trunks of trees.

Repellents are also probably less effective for the smaller pests. Sanitation can help to keep populations down by removing food sources that may draw the pests in. Orchard sanitation and field clean up can also help to reduce populations by removing food sources, and at the same time, removing protection. Rodents find protection in thick grass, rough or weedy areas, trash and leaf litter. They make tunnels or pathways under this cover, which allows them to move freely, out of sight of predators. By cleaning up these areas, whether by mowing, tilling or whatever, you open them up to the view of predators. Some people will also compress or pack the snow next to rows of plants, which prevents rodents from moving underneath and getting to plants. Encourage predatory birds or other animals by being conscious of the habitats that they prefer.

Trapping and poisoning can be effective ways to reduce the populations of some types of rodents. It is important to ensure that traps are properly set, both to be effective and to prevent inadvertent trapping or poisoning of non-target species. Bait stations should be replenished regularly.

Rodent Factoids
  • The name “rodent” comes from the Latin word “rodere” which means “to gnaw”
  • Rodents’ constantly growing upper and lower incisors must be constantly filed down
  • The smallest rodent weighs 7 grams at maturity
  • The largest rodent, the capybara, weighs about 80kg
  • Some rodents can squeeze into a space as small as a ¼ inch high
Rodent Factsheets
Beavers - AEP factsheet
Control of Porcupine Damage
Mice and their Control
Control of Pocket Gophers and Ground Squirrels

Birds

It isn’t possible to describe or list all the different types of birds that can show up and cause problems on your farms. It can vary year to year. Birds, like rodents, cause problems by their sheer numbers and the difficulty in keeping them out, although they tend to show up in large numbers all at once, in an overwhelming display.


Netted Haskap
Scare balloons and netting
Scare device (bird of prey)
Photos by Robert Spencer

Most birds will not typically damage fruit and vegetable plants directly, but reduce yields (often completely) by their feeding. Sometimes, they don’t completely remove fruit, but render it unmarketable, particularly in larger fruit. Their subsequent gastronomic activities (a.k.a. crapping all over everything) can also cause problems with marketability, buildings and the public. This same activity can also introduce non-crop species into orchards or other plantings.

Management of birds is similar to that of rodents, although on a wider scale. The method(s) that you choose may be limited by cost and likely will have to be varied, as nothing works forever.

Individual high value plants may be protected by excluding the birds using netting or covers. On a larger scale, this may not be feasible (although it is being done in some cases). Using noisemakers (such as propane cannons, loud speakers, etc) can be effective, but you should give consideration to long-term efficacy and to the neighbourhood. If you have neighbours, they may not appreciate what you are doing and might put a stop to your plans. Using other scare tactics, such as mylar tape, scare balloons, fake birds of prey, etc. can be quite effective, as can encouraging natural predators. It is important to remember to move devices frequently, as birds can become used to a deterrent. You’ve all seen pictures or cartoons of crows using a scarecrow as a roost.
Hunting and killing of birds really isn’t feasible, for a couple reasons. One, they are typically too numerous for killing them to be even remotely effective. Two, many of our bird pests are protected or there are restrictions on hunting / killing them.

Bird Factsheets
Starlings and their Control
Managing Bird Damage to Fruit and Other Horticultural Crops – big document from Australia

Rabbits and Hares

I’m not sure how much damage rabbits really do to our commercial crops in Alberta, but they reportedly do damage in other areas. Rabbits typically feed on new growth and buds but can also girdle trees by chewing off the bark at the base of trees and can prune branches off. It is pretty scary to see how much damage one cute, fluffy little bunny can do to a stand of trees.

Manage rabbits by encouraging their natural predators and by spreading/painting repellents on the bases of trees (as high as they can reach with snow). Trapping and shooting is also an option. Poisoning is illegal in Alberta (due to the impact on the other species further up the food chain). Exclusion on a local scale (either plant by plant or around orchards or gardens) can be effective, using mesh fences, cages or other mechanical devices. Removing undergrowth and exposing them to predators can reduce their activity in your crops.

Rabbit Factoids
  • Prolific reproducers – litters range from 1 kit up to 18
  • Average gestation period = 30-32 days
  • Rabbits live in groups called “warrens” in underground burrows
  • Rabbits re-ingest their own dropping to extract more nutrients from them
Related Factsheets
Control of Rabbits and Hares

Humans

I jokingly included humans in the list of potential vertebrate pests, but they really are potential pests that must be managed just like the other “animals”. Some of the pests might be customers. The best way to control human predation is to fence, post signs, educate and communicate. Try and train them in how to act appropriately or carefully in your plantings.

If you are experiencing problems with vertebrate pests, talk to your local Fish & Wildlife Officer for assistance, as they can tell you want is permitted for your area and may be able to recommend a solution.

Other Relevant Resources

Rodent and Deer Control in Orchards

Some Pest Control Suppliers

Margo Supplies Ltd
Wildlife Control Supplies Canada
 
 
 
 
Share via AddThis.com
For more information about the content of this document, contact Robert Spencer.
This information published to the web on October 31, 2016.