Pales weevil (21)

family Curculionidae

Preferred hosts are loblolly, pitch, shortleaf and white pines. This insect has also been reported on Douglas-fir, fir, hemlock, juniper, larch, northern white cedar, and spruce.

Description: Adult weevils are 7 to 12mm long, reddish-brown to black, with a prominent snout, and patches of light colored scales on the wing covers, and a line or patch of yellowish-white scales on the head. Larvae are legless and C-shaped, with white bodies and brown heads.

Life history: Adults become active between late April and early June, feeding on the bark of branches. They feed during the day and hide at night. After a short feeding period, they fly to cut, dead or dying pines, mate and lay eggs in the roots. Larvae construct long tunnels under the bark, and pupate in the sapwood. There is one generation a year.

Overwintering: Adults overwinter in the duff under conifers.

Adults: Adults chew a series of small holes in the bark which then cover with white, crystallized resin. If populations are sufficiently high, however, these areas may merge, girdling and killing plants up to 1cm in diameter. On larger trees, adults feed on twigs and terminals, and may cause dieback and deformed limbs.

Where trees are showing the typical signs of weevil damage, check for adult presence during the day in the duff under the trees.

Monitor for adults by placing 5 to 15cm pine discs under the trees to the underside of which discs the adult beetles will cling during the day.

Cultural: Delay replanting of trees for one to two years where trees have been cut. Remove stumps or treat stumps with insecticide. Leave some live branches on a stump tomake the live stump unattractive to weevils.

Chemical: Spray trees late April through June and again in August and September.

bendiocarb
chlorpyrifos
fenitrothion

Peachtree borer

family Sessiidae

Prunus species are the primary hosts, with wild and cultivated cherries, plum and peach being preferred.

Description: Adult males of these clearwing moths are shiny black with a black wedge-shaped anal tuft, a wingspan of about 28mm and a black band at the apex of each front wing. Mature larvae are about 31mm long, white with brown heads, and five pairs of ventral prolegs.

Life history: Adults are active from late June to early August. Young larvae begin to excavate tunnels in late summer near the tree crown. They overwinter in the tunnels and continue feeding again the following spring. There is one generation a year.

Overwintering: Larvae overwinter in tunnels.

Larvae: Larvae tunnel into the roots and lower trunk of plants, such that small caliper trees are frequently killed by their girdling activity in one or two years. Larger trees exhibit dieback of branches and gummosis with frass at the root crown.

Traps: A pheromone trap may be hung in May to detect the first emergence of males, although most adults do not emerge until early June in Minnesota ( when mock orange is blooming and most blooms on bridal veil spirea are brown).

Larvae: Look for dieback on Prunus species and look in spring for cracked bark, frass and gummosis at the root crown. There may be shed skins present in June through August.

Cultural: Avoid piling mulch high against the stems of Prunus species as this practice seems to attract borer egg laying.

Biological: The entomopathogenic nematode, Steinernema carpocapsae, can be sprayed at the root crown on damaged bark to control active borers. The spray will not be effective if borer holes are blocked by gummosis.

Chemical: A chlorpyrifos spray may be applied to the root crown in late May.

Steinernema carpocapsae
chlorpyrifos

Pear sawfly (57)

family Tenthredinidae

Cherry, cotoneaster, hawthorn, mountain ash, pear and plum

Description: Larvae are slimy and slug-like, and shiny olive-green in color. They are 12mm long when full grown. Adults are about 5 to 8mm long, black and yellow, and stout bodied.

Life history: Adults emerge early in June and lay single eggs on leaf undersides. Larvae appear in June, feed for about a month, then drop to the soil to pupate. A second generation can begin in early August.

Overwintering: Pear sawflies overwinter as prepupae in the soil.

Larvae: Larvae feed on the upper leaf surface, leaving only the leaf veins. Heavy defoliation gives the tree a scorched appearance and leaves may drop prematurely. Severe defoliation can adversely affect tree health.

Larvae: Look for black, slug-like larvae feeding in June and again in August on the upper surface of leaves.

Chemical: Horticultural oils and soaps are very effective against larvae.

Physical: Small populations of larvae can be removed by hand and destroyed.

horticultural oil
horticultural soa
wood ash
acephate
bendiocarb
bifenthrin
carbaryl
chlorpyrifos
cyfluthrin
fenitrothion
fluvalinate
malathion

Pear thrips

Taeniothrips inconsequens

order Thysanoptera

Apple, ash, beech, birch, cherry, and maple

Description: Adult pear thrips are about 1.5mm long, slender and brownish black in color. Larvae are pale white and translucent.

Life history: Adults emerge in early spring as buds and new vegetation are developing. Eggs are laid in leaf midveins or petioles. Larvae feed on leaves until July and then drop to the ground to pupate. There is one generation a year.

Overwintering: Pupae overwinter in the ground.

All stages of this insect, all of whom are female, feed on host plant foliage. Leaves become stunted, tattered and distorted. Defoliation sometimes occurs. Blisterlike scars may form at leaf midveins and on petioles where eggs have been laid.

Look for stunted, tattered and distorted foliage on host plants.

Chemical: If damage becomes unacceptable, spray with one of the suggested insecticides Treat foliage or flowers as soon as thrips are detected. Repeat applications on a weekly basis until populations are reduced to acceptable levels.

acephate
bendiocarb
cyfluthrin
diazinon
fluvalinate

Pine bark adelgid (31)

family adelgidae

White pine is the preferred host, but this adelgid also feeds on Austrian and Scots pines.

Description: Adults are about 3mm long, oval, black, usually wingless, and covered with fluffy white wax.

Life history: Overwintered immature females mature in late April in Minnesota and lay eggs that produce both winged and wingless forms. Wingless forms remain and reproduce on the pine host. There are several generations a year.

Overwintering: Immature females overwinter on bark..

The wooly white wax produced by this adelgid can turn large areas of trees white. It is doubtful, however, that even severe infestations can damage a healthy tree.

Look for the fluffy wax covering these insects on trunks and branches in early spring.

Check under the wax, both to monitor the pest stage present and also to determine the presence of natural enemies.

This adelgid does such little damage to healthy trees that control is not usually warranted. A dormant oil or summer oil may be used if absolutely necessary and no predators or parasites are present.

horticultural oil
horticultural soap
chlorpyrifos
cyfluthrin
diazinon

Pine needle scale (47)

family Diaspididae

Douglas fir, fir, hemlock, pine, and spruce

The mugo pine is most susceptible to severe injury.

Description: Adult females are white, oval-elongate scales from 2.5 to 3 mm long. There is a small orange or reddish cap at one end. Males are smaller, but similar. Eggs are purplish-red. Crawlers are reddish when active and yellowish when settled.

Life history: Eggs hatch in mid to late May and the mobile crawlers seek feeding sites on new needles where they settle and form their scale shell. Eggs are laid in the fall. There is one generation a year.

Overwintering: Overwintering is in the egg stage under scale covers.

Light to moderate feeding causes needles to turn brown and to drop prematurely. Heavy infestations can kill young trees and reduce vigor in mature trees.

Look for obvious white scale covers in mid-late May.

Pine needle scale crawlers begin to be active in Minnesota when both bridal veil spirea and horsechestnut are blooming. Look for both reddish active crawlers and yellowish settled crawlers. Check under covers for eggs. A hand lens will be useful for this purpose.

Physical: Prune out and destroy heavily infested branches.

Chemical: Scales are vulnerable in their overwintering stage to horticultural oils used as dormant applications. Oils should be applied in spring before plant bud break.

Crawlers are susceptible to contact insecticides, but these should only be used if parasite and predator activity is not observed. The best time to apply control measures is when the reddish crawlers hatch in May.

horticultural oil
horticultural soap
acephate
cyfluthrin
malathion

Pine root collar weevil

family Curculionidae

This weevil attacks Scots, Austrian, red, and occasionally eastern white pine. Scots pine is preferred.

Description: Adults are reddish brown to black in color with pale yellow flecks on the thorax and wing covers. They are 6 to 12mm long. Larvae are legless, C-shaped white grubs with a dark head.

Life history: Adults feed on branch bark near the ground in early spring and begin egg laying. Later they move to and feed in the upper crown branches. Eggs are laid throughout the summer. There is one generation a year.

Overwintering: Adults overwinter in the duff.

Larvae: Larvae feed just below the soil surface on the outer bark, inner bark and sapwood of stems and large roots. This feeding girdles the bark and restricts the transport of nutrients, thus weakening the tree and retarding growth. Eventually the tree’s needles will yellow and then turn a deep reddish brown. A swollen trunk at ground line and darkened . pitch-infiltrated soil around the root collar indicate an infestation.

Carefully monitor small trees (2.5-10cm in diameter) and trees growing in poor soil as these are usually most severely damaged.

Look for white pitch flow on bark and into the soil around the root collar during the growing season. You may have to dig a few inches into the duff to look for adults.

Cultural: Consider selecting pines which are seldom attacked, such as pitch or white pines.

Physical: Prune away lower branches and expose soil at the base of the tree.

Chemical: Apply insecticide to trunks and surrounding soil in mid-May before egg laying takes place and again in mid-August to control newly emerged adults. Apply enough spray to wet the tree’s root collar thoroughly and to soak the soil to about a 30cm radius

chlorpyrifos
diazinon

Pine sawflies (1 - 3)

(About 10 species of diprionid sawflies are pests of pine in the Mid-west. Also see red-headed pine sawfly.)

Family Diprionidae

Most native and imported species of pine are attacked by at least one species of sawfly.

Description: The fully grown larvae of sawflies are commonly from 18 to 25mm in length. They usually have more than five pairs of fleshy prolegs. They range in color from grayish to yellowish-green, often with brown or black stripes or spots. Adults are wasp or bee like, about 15mm long, and black to brown in color.

Life history: Young larvae feed in groups on needles beginning at the needle tip. Older larvae feed singly or in pairs. When disturbed, larvae rear up in a characteristic S shape. Larvae of most species drop to the ground and pupate in the soil. There may be one or sometimes two generations a year, depending on the species.

Overwintering: Most species overwinter as prepupae or pupae, but some do so as eggs.

Female sawflies lay eggs in needles causing yellow spotting.

Eggs: Look for yellow spots on needles.

Physical: Light, accessible, infestations may be hand removed and destroyed.

Chemical: Horticultural oil is effective against young instars. Other insecticides also provide good control but should only be considered after all other measures have been tried. Chemicals are less effective against full grown or nearly full grown larvae. All applications should be applied directly against areas where larvae are eating.

horticultural oil
acephate
carbaryl
chlorpyrifos
cyfluthrin

Pine spittlebug (36)

family Cercopidae

Primary host of the pine spittlebug is Scots pine, but it also feeds on eastern white, jack Japanese, loblolly, mugo, pitch, and Virginia pines. Other softwoods are also attacked.

Description: Adults are about 6-10mm long. They are tan colored with a thin white dorsal line through the head and irregular white bands on the wings. Nymphs are black with a white abdomen.

Life history: Eggs usually hatch in May. Nymphs feed under a frothy, spittle-like foam of whipped honeydew. Adults are present from mid through late summer but they do not make spittle. All stages of the insect feed on sap. There is one generation a year.

Overwintering: Eggs overwinter on bark.

Feeding by all stages, if populations are numerous enough, may cause twig and branch dieback. Heavy infestations in successive years may kill Scots pines.

Nymphs: In May and June, look under spittle for slow moving nymphs.

Physical: Light and accessible spittlebug infestations can be removed by hand or by a strong water spray.

Chemical: Light infestations have little effect on trees and control measures are usually not necessary.

If infestations are heavy, spray spittle covered areas with a residual insecticide in May.

bendiocarb
carbaryl
chlorpyrifos
cyfluthrin
fenitrothion

Pine tortoise scale (41)

family Coccidae

Though primarily a pest on jack and Scots pine, this scale also occasionally attacks Austrian, mugo, red, slash, Swiss mountain, and white pine.

Description: Adult female scales are reddish brown with black stripes, or cream colored markings. They are convex, and 3 to 6mm in diameter. Male covers are small, flat, and translucent, and the males themselves resemble gnats. Crawlers are reddish in color.

Life history: This scale is generally found on twigs. Crawlers hatch in late June to early July. There is one generation a year.

Overwintering: Immatures overwinter on twigs.

The conspicuous sooty mold that grows on their honeydew secretions is perhaps the first symptom of heavy infestation by these insects. Branch tip needles may yellow and then dieback may occur. Injury is most frequently suffered by seedlings and saplings, which can be killed in serious infestations , but mature trees may also be damaged.

In spring look for female scale covers on twigs at the base of needles.

In late June to early July, look for reddish crawlers.

Look for ants, which may become abundant, seeking honeydew and driving off natural enemies of the scales.

Look for honeydew and sooty mold.

Look for needle yellowing.

Physical: Prune out and destroy heavily infested branches.

Chemical: Scales are vulnerable in their overwintering stage to horticultural oils used as dormant applications. Oils should be applied in spring before plant bud break.

Crawlers are susceptible to contact insecticides, but these should only be used if parasite and predator activity is not observed. The best time to apply control measures is when the reddish crawlers hatch in late June to early July.

Spray the base of trees with chlorpyrifos if ants are active in large numbers.

horticultural oil
horticultural soap
carbaryl
chlorpyrifos
cyfluthrin
diazinon

Pine tube moth (16)

family Tortricidae

Eastern white pine

Description: Adults are tortricid moths, about 9mm long with wings closed. The forewings are brown with two whitish cross lines on each. Wingspan is about 14mm. Mature larvae are 12mm long, pale yellowish green with light brown heads.

Life history: Adults emerge in May and lay eggs on needles. Larvae live within a tube constructed by fastening from 5 to 20 needles together with silk. Larvae fed on the tips of these tube needles. There may be two generations a year, the second appearing in July.

Overwintering: Pupae overwinter in tubes.

Larvae consume the ends of their tube needles, and some tube needles turn yellow or die. Heavily infested trees have an untidy ragged appearance. Serious damage is not expected.

Look in May for pine needle tube formation on eastern white pine.

Physical: On small trees, or where accessible, hand pick pine tubes and destroy them.

Chemical: Chemical control measures are rarely necessary. If heavy infestations occur on large trees whose appearance is valued, spray with a residual insecticide.

acephate
cyfluthrin

Pine webworm (4)

family Pyralidae

Jack, red, and white pine are preferred in Minnesota, but loblolly, longleaf, mugo, pitch, shortleaf, slash and Virginia pines are also attacked.

Description: Adults are moths of the family Pyralidae and are about 13mm long with wings folded. On the forewings a central gray crossband separates a black base and tip. Wingspan is about 25mm. Full grown larvae are about 18mm long, yellowish brown with two dark brown to black longitudinal stripes on each side.

Life history: Adults are present from June to August. Eggs are laid on pine needles. Young larvae mine needles, but older larvae construct and live in silken tubes in masses of brown frass webbed together with silk. There is one generation a year.

Overwintering: Pupae overwinter in soil under trees.

The damage caused by the larvae of this pest is primarily aesthetic. The larval nests are ugly and give trees an untidy appearance.

In early June look for signs of mining in needles.

Physical: In light accessible infestations, remove frass nest by hand and destroy.

Chemical: If there is a lot of webbing present and signs of extensive needle mining, spray with any of the listed insecticides in June.

acephate
carbaryl
cyfluthrin
diazinon
fluvalinate

Pitch mass borer

Synanthedon pini

family Sessiidae

Pine and spruce

White pine is particularly preferred.

Description: Adults of this insect are clearwing moths. They have a wingspan of 25 to 30mm. Forewings are opaque and blue-black in color. There is a large orange patch under the abdomen, an orange band on segment 4, and a tuft of orange at the tip of the abdomen. Larvae are about 25mm long and white to pink in color with brown heads.

Life history: Adults emerge in June and July and lay eggs near scars or wounds, or under branches. Larvae bore into bark and sapwood. The life cycle requires two to three years.

Overwintering: Larvae overwinter up to two times in tunnels.

The principal symptom of damage by this insect is the mass of pitch, up to 8 to 10 cm in diameter, which accumulates at larval entrance holes. Larval tunneling does not usually kill trees.

Traps: Hang out a pheromone trap in June and July to determine the emergence time of adult males.

Carefully examine the trunk of trees directly below a branch for larval entrance holes and for the large amounts of pitch which usually seep from the borer wound. Look also for bark scars and wounds with frass, and for adult exit holes with pupal skins extruding.

Chemical: Apply a residual insecticide to the trunk after first adult males have been taken in a pheromone trap, or once per month in June and July.

chlorpyrifos

Poplar-and-willow borer (126)

Cryptorhynchus lapathi

family Curculionidae

This pest feeds on all poplar and willow species (in the genus Populus) except P. tremuloides. Alder and birch are also occasionally attacked.

Description: Adults of this insect are stout weevils with long curved snouts. They are about 8 to 10mm long, and are black in color with the exception of the apical third of the wing covers which is gray to white. Mature larvae are about 6mm long, cream colored, legless and C-shaped.

Life history: Adults emerge in spring and feed on the phloem of new shoots. In summer, females chew holes in the bark of stems into which they usually lay a single egg. Larvae bore into the bark, then into the wood, excavating long tunnels, the dust from which they push to the outside of the stem. New adults emerge in late July and August. Two years, possibly three, are required to complete the life cycle.

Overwintering: Young larvae overwinter in tunnels. Adults overwinter in the duff.

Larval feeding may kill young saplings. Frequently, the stems of willows and poplars are weakened and rendered liable to break in high winds. Trees may also become bushy.

Look for adults in the spring feeding on new shoots.

Look for holes in the lower part of stems with sawdust-like frass emerging.

Cultural: Use appropriate cultural practices to reduce tree stress.

Physical: Find, cut out, and destroy infected stems.

Chemical: Spray stem of host plants when adults are active on trees. Adults which have overwintered will be present in spring, feeding on new shoots. New adults appear in late July to August.

chlorpyrifos

Poplar borer (134)

family Cerambycidae

Poplars are the primary host but willows are also attacked

Description: Adults are robust gray to green long horned beetles with antennae as long or longer than their bodies. They are from 20 to 28mm long Larvae reach 30-35 mm when fully grown and are creamy white in color.

Life history: Adults emerge from late June through August. They feed on bark and lay single eggs in gnawed bark or exposed roots. Larvae tunnel inside the trunk and branches of hosts, feeding on phloem and sapwood. They pupate in the tunnel after plugging the hole with shredded wood. Adults chew through the plug and emerge from the hole. The life cycle takes 2 to 4 years to complete.

Overwintering: The first winter is spent as larvae in the sapwood. The second winter is spent as a mature larva in a cell at the end of the larval tunnel.

Sawdust-like frass on trunks exuding from borer holes is indicative. Other symptoms include black scars on the trunk, entrance holes in bark, and wet areas from sap leaking around holes. Larval feeding in wood weakens the tree structurally. Small trees are occasionally killed by larval girdling. Larger trees are made susceptible to wind breakage.

Look for adults in late summer.

Look for symptoms of borer presence throughout the growing season.

Cultural: Minimize tree stress to reduce borer problems.

chlorpyrifos

Poplar clearwing borer

Paranthrene dollii

family Sessiidae

Poplars, cottonwood and willow

Description: Adults are mimics of paper wasps. They are reddish with opaque, dark brown forewings and semi-transparent, reddish brown hindwings.

Wingspan is from 30 to 40mm. Legs are dark orange. Mature larvae are from 25 to 32mm long, white to pink, with a brown head.

Life history: Adults emerge in May or June. Eggs are laid in cracks or wounds, usually towards the base of the tree. Larvae feed on bark at first, then bore into wood. Two years are needed to complete the life cycle.

Overwintering: Larvae overwinter in tunnels.

Early symptoms of attack are sap and frass exuding from entrance holes, usually toward the base of trees. Infested trees are weakened and may suffer breakage.

Traps: Hang out a pheromone trap in May to June to determine the emergence time of adult males.

Carefully examine the the trunks, particularly at the base, of trees for larval entrance holes, or for bark scars and wounds with frass, and for adult exit holes with pupal skins.

Chemical: Apply a residual insecticide to the base of the trunk after first adult males have been taken in a pheromone trap, or once per month in May and June.

chlorpyrifos

Poplar leaf-petiole gall aphids (222)

Pemphigus spp.

Family Aphididae

Poplar, cottonwood

Description: Adults are 3mm long, white-green to green aphids with dark heads and thorax.

Life history: Eggs hatch in late April, and nymphs begin to feed at leaf bases. Globose galls are formed by mid-May There are three generations in about two months, and the final eggs are laid in old galls.

Overwintering: Eggs overwinter in old galls.

The aphids form a marble-shaped green gall on petioles at the base of poplar leaves. This genus is also a root aphid on the cabbage family and sugarbeets.

Control is usually not necessary.

Pesticide use is not usually necessary

Poplar tentmaker (70)

family Notodontidae

Various species of poplar and willow

Description: Adults of this insect are moths of the family Notodontidae. They are about 12mm long with wings folded, have a wingspan of about 25mm, and are brownish gray with three white lines crossing each forewing. Mature larvae can reach 42mm in length. They are grayish and have four light yellow lines on top, one bright line and several less distinct lines and yellow marks on the sides. There are black tubercles on the first and eighth segments of the abdomen.

Life history: Adults appear in April and eggs are laid under leaves. The gregarious larvae live in tents or webs that they construct by pulling the edges of leaves together and lining them with silk. They feed until October then crawl to the ground and pupate. There is usually one generation a year , but there may be two.

Overwintering: Pupae overwinter in cocoons on the ground.

Larvae consume all of a leaf except for the midrib and major veins. Host trees growing on an open site may be seriously defoliated

From May through Octobe look on poplars and willows for nests constructed from webbed leaves.

Physical: In light infestations and when accessible, hand remove larvae.

Biological: Bacillus thuringiensis is effective against early instars.

Chemical: For heavy infestations and later instars apply a residual insecticide.

Bacillus thuringiensis var. kurstaki
acephate
bendiocarb
carbaryl

Privet rust mite (231)

family Eriophyidae

Amur and California privet

Description: Adults of this eriophyid mite are white to yellow, less than 0.5mm long, and spindle shaped with four legs. Immatures are similar but smaller.

Life history: Mites become active as soon as new leaves develop. Several generations of mites overlap throughout the spring and summer.

Overwintering: Adults overwinter on twigs.

All stages of mites suck plant juices. Leaves become stippled and then cup or curl. Mites probably introduce toxins into the plants. Leaves turn olive green or brown.

As soon as leaves appear in spring, look for the minute yellow mites. A hand lens will be useful for this purpose.

Chemical: A dormant horticultural oil spray will control the overwintering population and contain spring outbreaks.

An oil or soap spray may be applied in spring if mite numbers warrant.

horticultural oil
horticultural soap
carbaryl
diazinon