Backyard Pests
The following information on common backyard pests was compiled by the PFRA Shelterbelt Centre.
Host: All trees and shrubs.
Appearance and Life History: Aphids, commonly known as plant lice are small, pear-shaped, fragile insects. They can be black, red, green, yellow or colorless, with some species being covered with long, white, waxy threads. Aphids may be winged or wingless and measure 1 to 3 mm in length. They can usually be identified by a pair of short, tube-like projections near the rear of the abdomen. Aphids have long antennae and slender legs and are equipped with piercing/sucking mouthparts. The life history of most aphids is complicated with many variations and exceptions.
Damage: Aphids cause damage by piercing the tender plant tissue and drawing large quantities of plant sap. They may be found feeding on any part of the host including: the foliage, buds, flowers, fruit, twigs and roots. They often feed in groups. Aphids can cause galls, curled leaves, swollen branches, and discolored or wilted leaves. They usually do not cause permanent damage to forest, shade and ornamental trees. Some aphids excrete excessive amounts of a sticky substance called honeydew. This honeydew can be extremely annoying when it is deposited on sidewalks, cars and other objects. Honeydew attracts insects such as ants, bees, flies and wasps, whose presence may be the first sign of an aphid infestation.
Control: Aphids have many natural enemies including lady beetles and birds. Weather conditions such as heavy rains or cold temperatures are major factors in reducing aphid populations. However, under favorable conditions, aphid populations can rapidly increase and may require chemical control. Insecticides registered for control of aphids include: malathion, diazinon, dimethoate, permethrin and pirimicarb. Before applying any insecticide check for predators, the amount of aphid damage and make sure the insecticide is not toxic to the plant.
Host: Green Ash
Appearance and Life History: In the prairies, the ash plant bug completes two generations during a growing season. The plant bug overwinters in the egg stage with nymphs first emerging in mid-May just as the ash leaves begin to unfold. The nymphs are small, oval shaped and vary from yellowish-green to dark brown. Adults measure 4 to 5 mm in length, 1.5 to 2.0 mm in width, and range from light green to black. First generation adults are found from early to late June while second generation adults are present and laying overwintering eggs from early August to late September.
Damage: The ash plant bug causes damage to the host by inserting its mouthparts into the leaf tissue and sucking out the plant sap. Damage by the plant bug is cumulative throughout the year, so that a light infestation in the spring may result in severe damage by the fall. Damage ranges from a yellow stippling on the upper leaf surfaces to wilted and deformed leaves, resulting in premature leaf drop, and reduced annual growth. This elusive insect is often difficult to find, but an indication of an infestation is the varnishlike black excrement spots which remain on the damaged leaves.
Control: During a severe infestation, the following insecticides may be used: carbaryl, deltamethrin, diazinon or dimethoate. Spraying should be done in mid May to early June and again in mid July to early August to control adults prior to the egg-laying period.
Host: Maple, elm and ash.
Appearance and Life History: There are two species of cankerworm, spring cankerworm and fall cankerworm. Adult spring cankerworms emerge and deposit eggs in late March and throughout April, whereas fall cankerworm adults emerge and deposit eggs from late September throughout October. Adult males are small-bodied, brownish-grey moths with a 25 mm wing span, whereas females are dark brownish-grey, wingless and 12 mm in length. The larvae of both species emerge in the spring just as the leaves begin to appear and will feed on the foliage until mid-June. Full grown larvae measure 30 mm in length and they range in color from yellowish-green to brownish-green to black. The only means to distinguish cankerworm during the larval stage is to view the false legs at the rear of the caterpillar. Spring cankerworm have two pairs of false legs compared to three pairs on the fall cankerworm. When feeding is complete, the larvae enter the soil where they remain until they emerge as adults, that fall or the following spring depending on the species.
Damage: Cankerworm cause damage by defoliation during the larval stage. Initial feeding causes a shothole appearance in the leaves, but advance feeding results in the entire leaf being consumed except for the main veins. Most trees will re-leaf within three weeks after a severe attack. Trees that are defoliated several years in a row will show branch die-back in the crown area.
Control: If you have a small number of trees, tree banding is an effective method for controlling cankerworm. The bands are covered with a layer of sticky adhesive which prevents the wingless females from climbing the trees to lay eggs. For the spring cankerworm, the bands must be in place from mid- March to late April, whereas for the fall cankerworm, the bands should be in place from late September to early November. Chemical control can be achieved by using carbaryl or methoxychlor. A biological insecticide known as Bacillus thuringiensis is a safe alternative to chemical control.
Host: Trembling aspen, poplar and other trees and shrubs.
Appearance and Life History: Larvae emerge from egg bands in the spring, just as the foliage begins to appear on the trees. Larvae are dark brown with broad blue bands along each side and marked with a row of white key-hole shaped markings down the centre of the back. Contrary to their name, forest tent caterpillars do not construct a tent, but feed openly on the foliage. By mid to late June, the full grown larvae are 45 to 55 mm in length. The moths are present from mid-July to early August. After mating, the females deposit egg bands containing 100 to 200 eggs on twigs of host trees. The egg bands are 10 to 20 mm long and are covered with a foamy, dark-coloured, protective substance. The forest tent caterpillar completes one generation a year.
Damage: Forest tent caterpillar damage can range from a thinning of the crown to complete defoliation. After a severe attack most trees will refoliate the same year. Trees may suffer top dieback or die if defoliated three or more consecutive years.
Control: Natural factors such as disease, parasites, predators, starvation and adverse weather usually keep populations low. Where practical, some control can be achieved by removing the egg bands from the host trees late in the fall or early spring. For large shelterbelts, the larval stage may be sprayed with an insecticide such as malathion, acephate, carbaryl, deltamethrin, or Bacillus thuringiensis. Malathion, deltamethrin, and Bacillus thuringiensis are also registered for aerial application. Application of insecticides should be conducted in late May to early June while larvae are small and damage is light. Spraying will probably be required if the number of egg bands on the tree is greater than the trunk diameter in centimeters, measured at approximately 1.5 m above ground level.
Host: Scots pine, Colorado spruce, white spruce and other pines and spruces.
Appearance and Life History: Pine needle scale is a microscopic insect that overwinters as an egg under the scale formed by the mother. Nymphs emerge in early June and search for suitable feeding sites on old needles. In 3 to 4 weeks the male nymphs form a narrow, white, waxy protective scale about 1.5 mm in length. Meanwhile the females remain as free-feeding insects without a scale covering. During the next 3 weeks the males develop into winged adults and emerge from the scales to mate with the wingless females. By mid-August the females produce a smooth, white, oblong shaped scale about 3 mm in length. Each female produces about 40 overwintering eggs under the protective scale. There is one generation per year.
Damage: Pine needle scale causes damage by inserting its mouthparts into the needle and extracting sap. This feeding causes a yellowish-green area to form around each puncture. In severe cases the yellow spots merge, needles drop prematurely and the tree assumes a dull, unhealthy appearance. A severe infestation would be 20 or more scales per spruce needle and 50 or more per pine needle. Trees with repeated heavy infestations have reduced vigor and annual growth and become more susceptible to secondary insects.
Control: Lady beetles, parasites and weather contribute to the natural control of the scale. When natural controls fail, serious damage can be prevented by applying insecticides. Insecticides recommended include: dimethoate, malathion, diazinon or carbaryl. Two applications may be required; once in mid-June when nymphs are unprotected and searching for feeding sites, and a second in early August to control the females before they produce their protective scale covering.
Host: Poplar.
Appearance and Life History: The poplar budgall mite is about 0.2 mm long and is visible only with a microscope. All life stages overwinter within the galls. Mites are active within the galls from April to October, completing a generation every 2 to 3 weeks, which results in 8 or more generations per year. From May to August, some of the mites migrate to new, unfolding leaves, where they begin feeding by sucking the plant sap.
Damage: During feeding, the mites inject a substance that causes a woody, cauliflower-like gall to form. The mites are protected from predators and insecticides while inside the gall.
Newly formed galls are soft and green, but later in the summer become hard and brick red. Galls may grow to 3-4 cm in diameter. Galls tend to be more abundant on the lower branches. Infested branches are stunted, crooked, and have sparse foliage. Several years of attack result in branch dieback therefore reducing the aesthetic and shelter value of the tree. Galls can persist on the tree for 5 years or more. Infested trees become stressed and more susceptible to secondary insects and diseases.
Control: No pesticides are currently registered for control of this mite. Annual pruning and burning of galls will reduce infestations on individual trees but this is not practical for plantations. Pruning should be done in the fall when the trees are dormant and the mites are in the galls. Planting resistant clones is the best long term solution. Hybrid poplars such as ‘Walker’, ‘Assiniboine’, and ‘Manitou’ are resistant to poplar budgall mite whereas ‘Northwest’ is very susceptible. ‘Assiniboine’ and ‘Manitou’ have the added benefit of being male clones and therefore do not produce seed fluff.
Host: Choke cherry, rose, and cotoneaster
Appearance and Life History: Larvae emerge from eggs in the spring, just as the leaves begin to appear. The larvae have blueish-grey sides, and reddish-orange backs that are interrupted with a white stripe down the center. By early to mid-July the larvae are full grown, ranging from 40 to 50 mm in length. Moths emerge in early August, depositing egg masses containing up to 500 eggs each. The egg masses are deposited on twigs and branches and covered with a greyish foam-like substance. The Prairie tent caterpillar completes one generation per year.
Damage: Almost immediately after the larvae emerge, they construct tent-like webs in the branches. Caterpillars feed on foliage outside the tent, but return to the nest during adverse weather conditions. As the larvae develop, the tents are enlarged until they are unsightly masses of webbing containing excrement, casted larvae skins and larvae. Defoliation is usually confined to the odd branch, but there have been outbreaks where trees have been completely defoliated. Severely-infested trees may be temporarily disfigured and unsightly, but will not be permanently damaged.
Control: Prairie tent caterpillar damage can be reduced by picking off and destroying the egg masses on trees in late fall or winter when they are easily seen. Caterpillar populations can also be reduced by removing and destroying tents on cool days when most of the larvae are within the nest. Chemical control of the pest can be achieved using acephate, Bacillus thuringiensis, carbaryl, deltamethrin, or malathion.
Host: Colorado spruce, white spruce, balsam fir and other spruces.
Appearance and Life History: In July to early August, spruce budworm moths deposit about 100 eggs each, in clusters of 15 to 50 on the underside of needles. Within two weeks, larvae emerge and begin to construct overwintering shelters of silk. The larvae do not feed prior to overwintering. Shortly before the buds begin to expand in the spring, the small larvae begin feeding on old needles. As the buds break the larvae move to the new succulent needles and feed for 3 to 5 weeks. Full grown larvae are 20 to 25 mm in length and have a shiny dark-brown head and a reddish-brown body with whitish or yellowish spots. Pupation occurs within the trees, with adults emerging in about 10 days. The budworm has one generation per year.
Damage: Initially the larvae mine the previous year’s needles and cause minimal damage. When the larvae move to the new needles, they form protective shelters by tying the needles and developing shoots together with webbing. Each larva may construct several shelters during their development. Damage is often most noticeable in the crowns of the trees where the foliage appears reddish-brown and scorched. The larvae are wasteful feeders and leave dried, partially consumed needles on the trees. During severe infestations, the budworm can completely defoliate all new foliage along with some old needles. Repeated severe infestations can kill the tops of the trees in 3 years and whole trees in 5 years.
Control: Spruce budworm populations are generally regulated by natural factors and require control only during epidemic outbreaks. Where practical, hand pick the larvae from the tree early in the season. Insecticides registered for budworm control include: Bacillus thuringiensis, dimethoate, malathion and trichlorfon. These products are also registered for aerial application.
Host: Colorado and white spruce.
Appearance and Life History: The spruce spider mite completes up to 8 generations a year. Adult mites are microscopic (0.5 mm) and dark green to dark brown in color. Feeding begins in mid-May and continues throughout the growing season. Over-wintering eggs are produced from September until a severe frost.
Damage: The spruce spider mite injures the needles by inserting its slender mouthparts and sucking out the sap. The puncture causes a stippled, bleached discoloration. In severe infestations the needles become dingy yellow or brownish and often needles dry and drop off. Damage is usually first noticed on the lower inside branches but spreads upward and outward as the infestation progresses. The mites spin fine silken webbing throughout the twigs and needles. The webbing is most noticeable on the underside of the branches where dust particles, dead needles and dead mites adhere.
In spruce plantings, infestations can persist for years resulting in reduced tree vigor and eventually death. Recently planted trees, nursery seedlings, or trees under stress are especially susceptible to serious injury. To check for mite infestations, vigorously shake a branch over a piece of white paper, then rub your hand across the paper or press the paper in half. If red smears appear, mites are probably present. Trees should be checked regularly since mite populations can increase rapidly.
Control: Heavy rain accompanied by high winds and extreme temperatures are means of natural control. Some control can be achieved by washing infested trees with a strong jet of water. For shelterbelts or large trees, the following insecticides can be used: diazinon, dicofol, or malathion. Insecticides must be applied at high pressure so the spray penetrates the inner branches and webbing. A second application may be required two weeks after the initial spray.
Host: Colorado and white spruce.
Appearance and Life History: Adult yellowheaded spruce sawflies emerge in the spring just as the buds on spruce trees are beginning to swell. Females deposit eggs singly into the base of new needles. Larvae emerge within two weeks and begin feeding on the succulent needles. By early to mid- July the larvae are full grown and are about 20 mm in length. Full grown larvae have brownish-orange heads and green bodies marked with six greyishgreen stripes. Fully developed larvae drop to the ground and overwinter in cocoons in the soil. The sawfly completes one generation per year.
Damage: Larvae of the yellow-headed spruce sawfly initially feed on the new needles, leaving only short brown stubs. Once the new growth is devoured, the larvae move back on the branch and feed on the older needles. By July, infested trees appear ragged and yellowish-brown especially near the tops. Heavilyinfested trees may be completely stripped of foliage. Three to four consecutive years of moderate to heavy attacks can kill the tree. The yellow-headed spruce sawfly prefers young, open grown trees, resulting in extensive damage to spruce used in plantations and shelterbelts on the Prairies.
Control: Infestations on a few small trees can be controlled by picking off and destroying the larvae when they are first noticed. For shelterbelts or large trees, chemical control can be achieved with one of the following insecticides: acephate, carbaryl, diazinon, dimethoate, malathion or permethrin. Insecticide application should be made when damage is first noted.
