Vertebrate Pest Management

Table of Contents

1. Introduction
2. Description, Biology, Damage
   • Table 1. Common Vertebrate Pests of Apple Orchards
3. Management
   • Table 2. Cultural and Preventative Measures to Manage Vertebrate Pests
   • Meadow Voles - Baiting
   • Woodchucks - Poisoning
   • Rodents, Rabbits, and Deer - Shooting
4. Pictures
5. Related Links

Introduction

There are several vertebrate pests that can cause economic damage in apple orchards. These include several species of birds (crows, starlings, grackles, etc. and a number of mammal species including voles (often referred to as field mice), woodchuck, rabbits, and deer.

No single method of vertebrate pest management is completely effective. Often a season long management strategy, including cultural, mechanical, and biological methods and deterrents, is the most effective way of minimizing economic losses from these animals.

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Description, Biology, Damage

Table 1. Common vertebrate pests of apple orchards.

Species	Description	Biology	Habitat	Distribution	Damage
Crows, Starlings, grackles, other black birds	Various	Starlings, grackles and other black birds often flock together and pass through orchards near or at harvest. Crows are more solitary or in small groups.	Adapted to wide range of habitats. Crows often nest in conifers, such as pine plantations.	Common throughout Ontario.	Birds occasionally peck apples. This injury is most often seen on well-exposed fruit at the tops of trees.
Meadow vole (field mouse) Microtus pennsylvanicus	Body 90-130mm long; dark chestnut brown with grayish belly. Ears smaller and tail shorter (35-65mm) than that of mice.	Feeds on grasses, sedges, seeds, grains and tree bark. Makes surface runways in grass. Nests at or just below ground. Active day and night. Litters of 3-7 are produced throughout year. Population levels fluctuate widely, with a 3-4 year cycle.	Grasslands, meadows, fence rose, with plenty vegetation and orchard sods	Common throughout Ontario.	Feeding injury and girdling of bark of apple trees, particularly in winter when cover is present. May result in tree stress or death.
Pine vole, Pitymys pinetorum	Body 70-110mm long; auburn brown fur, very thick and soft. Tail shorter than meadow voles at 17-25mm.	Feeds on tubers, bulbs, seeds and root bark. Tunnels through leaf mould and loos topsoil layers near surface. Nests beneath logs stumps and other cover.	Most often found in Eastern deciduous woods, occasionally in orchards.	Present south of line between Goderich and Ottawa.	May tunnel around orchard trees and feed on bark of roots and young, feeder roots. Results in tree stunting or, sometimes, death if feeding is extensive. Damage to apple orchards has only been observed rarely in southwestern Ontario.
Woodchuck (Groundhog) Marmota monax	Body 40-5cm long; heavy-bodied; yellowish brown to brown, pale brown belly. Feet dark brown or black; tail 10-18cm. Weight ranges from 2.2-4.5kg.	Generally diurnal, feeding on a wide range of young, succulent plants. Dens in underground burrows with 2 or more openings. Breeds once a year with 2-6 young born in April or May. Hibernate during winter.	Open woods, ravines, regeneration areas, orchards.	Common throughout Ontario.	Damage ranges from bark injury due to gnawing teeth sharpening or tree climbing to root damage caused by burrowing. These burrows may also be a hazard to equipment and people who may inadvertently step into the hole resulting in possible physical injury.
Eastern Cottontail Sylvilagus floridanus	Body 35-45cm long with rather short ears (65-75mm) for a rabbit. Colour brown to grey with white cottony tail. Feet whitish. Weight ranges 1.0-1.8kg.	Feeds on green vegetation in summer, bark and twigs in winter. Nocturnal with activity from early dusk to late morning. Dens in brush piles, high vegetation or in shallow underground burrows. 3-4 litters per year, each with 4-7 young born. Populations are cyclical.	Open woods, heavy brush, regeneration areas.	Common throughout southern Ontario below line from Parry Sound to Ottawa.	During winter feed low on tender terminal growth and fruit buds, resulting in "witches broom" growth. Girdling of bark results in loss of tree vigour or death.
European Hare (jackrabbit) Lepus europaeus	Body 63-70cm long with long ears (11-13cm). Brownish grey colour; tip of tail black. Weigh up to 4kg.	Feed on green vegetation in summer, twigs and bark in winter. Active from early dusk until morning. Several broods per year.	Open fields and low hills.	Confined to southern Ontario below Algonquin Park. Most common in south-western and south-central Ontario.	Similar to Eastern cottontail but damage to upper limbs (within 1 metre of ground) more severe due to the ability of this animal to stand on hind legs to get hard to reach limbs.
White-tailed Deer Odocoileus virginanus	Height 90-110cm. Largest North American deer with females up to 110kg and males up to 180kg. Fur blue-grey to brown. Males have antlers. Long white tail is characteristic.	Browses on twigs, shrubs, herbaceous plants, acorns, and grasses. Active mainly at dusk until dawn. 1-2 young per year. Congregate in "wintering grounds" that may include orchard location sites.	Deciduous woods, open brush, regeneration areas, second-growth forests.	Common throughout Ontario, south of Timmins.	In winter and early spring will feed on soft tender tips and terminal growth. This "nipping" results in loss of fruit buds, and more importantly, tree shape. Smaller trees may also be damaged by rubbing of antlers to remove "velvet", polish or serve as communication posts. This injury occurs in the fall (Sept. to mid-Nov.)

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Management

A combination of cultural practices and preventative techniques, as part of a season long management strategy are the most successful in reducing economic losses from vertebrate pests (see Table 2).

The use of poison baits and shooting should only be used as a last resort if economic injury has occurred or is imminent.

¹Note that predators are rarely 100% effective in eliminating a vertebrate pest problem. However, they can impact population of voles, groundhogs and rabbits and therefore should be encouraged to reside or use orchards as hunting grounds.
²Control measures listed here should be considered only as a last resort to preventing economic losses from vertebrate pests.

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Meadow Voles - Baiting

When using poison baits for vole control avoid broadcasting on the orchard floor or using poison-coated corn baits. Such baits are also poisonous to farm pets, wild turkeys, pheasants, raccoons, skunks, and other non-target wildlife.

The use of bait stations provides a means of achieving a longer period of control of mice than the broadcast treatment. Various materials such as slabs of wood, pieces of board, or tin cans with one end removed can be used for bait stations. The bait is placed under the board, or in the can with the can lying on its side. The inverted-T bait station made of 1 1/2 inch ABS pipe is perhaps the most effective type of bait stations available. The this station several teaspoons of bait are placed in the neck that is capped, thus, protecting the bait from the elements. Bait stations should be used at a rate of approximately 25 per hectare (10 per hectare).

Bait stations are most effective if dropped apples are picked up and removed from the orchard before first snowfall. Common rodenticides used as bait are zinc phosphide-treated baits, dipacinon (Ramik Brown), and chlorophacinone (Rozol, Groundforce).

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Woodchucks - Poisoning

The following are commonly used methods of control for woodchucks:

Phostoxin - a fumigant that contains aluminum phosphide. In the presence of moisture, phosphide gas (phosphide) is released, that is claimed to be effective against groundhogs. When handling phostoxin, a full-face mask respirator with an acid gas canister should be worn and the sue of cotton gloves is recommended. A second person with personal protective equipment should be assisting during the fumigation. Always consult the product label. This product is manufactured in tablet form. Rate of application is one tablet per hole. All entrances must be sealed to prevent the gas from escaping.

The distributor of this material, Abell Waco Ltd., requires the user to take instruction on using this product before it can be purchased. A factsheet, Aluminum Phosphide for Groundhog Control, is available from the Ontario Ministry of the Environment.

Gas Cartridges - cardboard cylinders containing a mixture that burns slowly and asphyxiates the groundhog. The cartridge is placed in the burrow of the groundhog and all entrances must be sealed. Follow manufacturer's instruction on the preparation and use of cartridges.

Trapping - can be effective for groundhog control; however, it is time-consuming. The use of No.2 steel traps (muskrat traps) are most practical. traps should be checked at least twice a day and cleaned after each catch.

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Rodents, Rabbits, and Deer - Shooting

Rabbits and woodchucks where a problem, can be shot all year. Deer hunting is only permitted during prescribed dates allowed by the Ministry of Natural Resources. A landowner is not allowed to kill deer while defending his/her property. Check with hunting license issuers, your local Municipality, or local Ministry of Natural Resources offices for deer hunting season dates, and how to obtain permits.

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Pictures

Figure 1. The meadow vole is the most common "mouse" found in orchards.

Figure 2. Fresh footprints in snow indicate vole activity in winter.

Figure 3. Vole feeding injury to bark of apple tree.

Figure 4. Extenseive pine vole injury to roots and lower trunk.

Figure 5. White latex paint mixed with thiram, repels rodents.

Figure 6. White-tailed deer.

Figure 7. Deer-feeding injury to young shoots.

Figure 8. Mesh tree guards are highly effective in preventing rodent injury.

Figure 9. T-bar bait stations are efficient and prevent non-target poisonings.

Figure 10. Crow damage to Empire fruit.

Figure 11. Red fox feeds on voles, rabbits and woodchucks.

Figure 12. Small rodents are an important part of the American kestrel's diet.

Related Links

• Ontario Ministry of the Environment

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