MNLA Pest Newsletter, April 2006, no: 2 |
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http://www.entomology.umn.edu/cues
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Red maple flowers in April Photo:
Tree Canada Foundation |
Photo: Spruce budworm larva |
Vera Krischik and Mary
Rogers, Department of Entomology, |
Landscape and Nursery |
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Asian
ambrosia beetle References: |
Time: Females emerge from trees from April to July to bore into trees and lay eggs Hosts: Honeylocust, redbud, peach, plum cherry, persimmon
The Asian ambrosia beetle was first discovered in the U.
S. in South Carolina in 1974. It is found from Florida to Texas; east to
Virginia, Maryland, and Delaware; and north to Michigan
and Indiana. It is a pest of nursery stock. In Smaller branches or caliper trees are most commonly attacked. All life stages can be found inside the galleries. Eggs are laid in this tunnel, and the young larvae hatch and chew out small egg cradles that radiate from the adult tunnel like teeth on a comb. The larvae apparently do not eat wood; they feed on ambrosia fungi that grow on the surface of the wood in the tunnels and egg cradles. Female ambrosia beetles possess specialized structures called mycetangia in which the ambrosia fungus is carried in from one host plant to the next. Infestations normally can be identified by toothpick-like spines of boring dust protruding from holes made in the host plant by females excavating their galleries. Unlike other scolytids, which normally attack only stressed or damaged plants, Asian ambrosia beetles attack apparently healthy plants. Individual plants may host up to 50 beetles. It is almost impossible to save heavily infested plants. When mature, females leave infested plants and fly to new host plants. Males do not fly. There are several generations per year. Trapping: In a Japanese beetle trap place 70% ethanol in a pop bottle with a rope wick. AAB are attracted to traps baited with ethyl alcohol in the spring and early summer and the trap numbers correlate very well with attacks on trees most of the time. In the mid summer to fall and winter, trap catch with ethanol does not adequately represent the AAB present.
Research
at the The black twig borer, Xylosandrus compactus, is one of the few ambrosia beetles that attack many kinds of trees and shrubs that appear to be in good health. Over 224 plant species in 62 families are susceptible to the black twig borer. |
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Mossy rose gall Spiny rose gall (Hymenoptera: Cynipidae) References: |
Time: May, June
Hosts: Roses Mossy rose galls are caused by a cynipid gall wasp. These galls are common on wild roses of North America, from Ontario to Alberta in Canada and throughout most of the northern United States. They are becoming common on Rugosa cultivars. The presence of these insects is indicated by the formation of spherical, golf ball-size, spiny galls on the canes of host plants. Hybrid rugosas are particularly susceptible to this disfiguring gall. The development of these galls is stimulated in the spring by newly hatched larvae. The galls encase the larvae until adult wasps emerge the following spring. The galls are unsightly and alter the plant's shape. They also stress the host plant, behaving like nutrient sinks, drawing nutrients away from the rest of the plant. Large numbers of galls can result in death of the plant. The most effective control is physical removal and disposal of galls in autumn after leaves have dropped and galls are visible. It is important to dispose of all galls since even a single missed gall can produce and reintroduce 30 to 40 mature wasps to the garden the following spring. Imidacloprid soil applications might be effective. |
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Roseslug sawfly Bristly roseslug
sawfly
Curled rose sawfly (Hymenoptera: Tenthredinidae) References: |
Time: May, June
Hosts: Roses Three species of sawflies feed on rose foliage. All three species are light green with orange heads and late larvae can reach 3/4 inch (19 mm) in length. Rose sawflies "skeletonize" leaves by chewing away a layer of the leaf except for the veins. The thin layer remaining turns clear or brown between the uneaten veins. The older larvae of the bristly roseslug and curled rose sawfly chew holes rather than skeletonizing the leaves. Begin to scout for sawfly larvae in early May. Roseslugs feed through June and are not seen again until the next spring. The curled rose sawfly also has one generation per year. The bristly roseslug has several generations throughout the summer. Sawflies often feed on the undersides of leaves, so inspect all leaf surfaces. Sawflies are small, dark, non-stinging wasps. Sawfly larvae skeletonize rose leaves. These larvae resemble butterfly or moth caterpillars, but can be identified by the number of fleshy legs (prolegs) that follow the front three pairs of legs. Sawflies have five or more pair of prolegs, while caterpillars have less than five. Avoid spraying the rose flowers, as many conventional insecticides are highly toxic to bees. Use acephate (Orthene), carbaryl (Sevin), bifenthrin (Talstar) or a soil drench of imidacloprid. |
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Eastern tent
caterpillar References: IPM of Midwest Landscapes (UMN)
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Time: April
Hosts:
Apple, crabapple, pear,
plum, and wild cherry are preferred, but a wide variety of other forest, fruit
and shade trees are hosts. Overwintered eggs hatch as host tree buds begin to unfold in the spring. Larvae are gregarious and construct a communal web or tent, which grows as they develop and from which they emerge to feed. There is one generation a year. Black egg masses overwinter on twigs. Silken webs in tree forks may be unsightly. When infestations are sufficiently severe, trees can be completely defoliated. Eggs hatch when red maple blooms in the first week of April (Herms). Look for larval silken tents on preferred hosts in early April. Also look on preferred hosts in the dormant season for approximately 18 mm long, black egg masses. Adult moths are light brown, 25 mm long, with two diagonal white stripes across the forewings. Wingspan is 37 to 50 mm. Larvae can grow to 50 mm or more in length. They have black heads, a white stripe down the length of the back and yellow lateral stripes with blue spots. In the dormant season, prune and destroy egg masses. Destroy webs and their contents as soon as they appear. Chemical control: Use Bacillus thuringiensis var. kurstaki when trees are flowering to protect pollinating bees. Spray foliage when tents first appear. Biological control: A diverse assemblage of parasitoids and predators attack this highly conspicuous species. These include parasitic wasps Hyposoter spp. (Ichneumonidae) and Bracon spp. (Braconidae), tachinid flies, hornets, yellow jackets, ants, predatory stink bugs, and birds. Epizootics of an NPV virus decimate populations in peak years. Biorational pesticides: Bacillus thuringiensis var. kurstaki, diflubenzuron, insecticidal soap, pyrethrin, spinosad, tenbufenozide. Conventional pesticides: acephate, bifenthrin, carbaryl, chlorpyrifos (nursery only), cyfluthrin, malathion, permethrin. |
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Forest tent
caterpillar References: |
Time: Mid to late May
Hosts: Alder, aspen, ash, basswood, birch,
cherry, elm, hawthorn, maple, oak, peach, poplar, willow and flowering fruit
trees Young larvae hatch when leaves are beginning to unfold in mid- to late May. Colonies of larvae stay together and move about in single file. They do not make silken tents. Cocoons are constructed within folded leaves or bark cracks. In mid summer, eggs are deposited in black masses, which encircle twigs. There is one generation a year. Black egg masses overwinter on twigs. Look for shot holes in foliage from mid to late May when larvae begin to be active. Feeding is complete by the end of June. It is important to detect serious infestations early to prevent defoliation. Where possible, egg masses can be cut from trees and destroyed. Small populations of larvae can also be physically removed. Adult moths are buff-colored with two darker oblique bands on the forewings. Wingspan is 25 to 38 mm; adults are approximately 18 mm long with wings folded. Mature larvae are approximately 50 mm long, blue and gray with oval white spots along the back. Chemical control: Bacillus thuringiensis var. kurstaki can be sprayed to control young larvae. Larger populations of older larvae can be controlled with a residual insecticide. Biological control: The large gray parasitic fly, Sarcophaga aldrichi, often becomes very abundant during forest tent caterpillar outbreaks. Known as the friendly fly, this native parasite lands on any object, including people. This insect is very important for naturally reducing forest tent caterpillar outbreaks. Hyposoter spp. (Ichneumonidae) and Bracon spp. (Braconidae) are also parasitoids of forest tent larvae. An NPV virus and a fungal pathogen, Entomophthora, also can occur in outbreak populations. Biorational pesticides: Bacillus thuringiensis var. kurstaki, diflubenzuron, insecticidal soap, pyrethrin, spinosad, tenbufenozide, pyrethrin. Conventional pesticides: acephate, bifenthrin, carbaryl, chlorpyrifos (nursery only), cyfluthrin, malathion, permethrin. |
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Forestry, Christmas Tree, Landscape |
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Balsam twig aphid References: |
Time: May to Aug
Hosts:
All species of fir, balsam and Fraser,
some spruce and pine species.
There are three stages of aphids which appear during the year:
brown-gray, wingless females, followed by blue-gray forms with a white waxy
covering, and then by winged forms capable of migrating. There are several
generations per year. Eggs overwinter on bark.
Needles may become deformed or glued together by sticky
honeydew, so that they subsequently yellow and fall prematurely. New spring
growth may be stunted or deformed and the bark roughened.
As buds swell, look for wingless females on buds. Also look
for white forms on new needles in June. Look for curled needles as a result
of aphid feeding, and for copious amounts of honeydew.
Cultural control: Avoid planting trees too
close.
Chemical control: Horticultural oil can be
applied as a dormant spray if eggs are detected in large numbers.
Applications of well-timed sprays may be used in spring if numerous
overwintering aphids are present on new growth.
Biological control: Ants, yellow jackets,
bigeyed bugs, damsel bugs, assassin bugs, minute pirate bugs, lace-wings,
earwigs, predatory thrips, lady beetles, ground beetles, soldier beetles,
hover fly larvae, and predaceous midges are all important predators. Aphidius
wasps (Braconidae) are important parasitoids.
Biorational pesticides: insecticidal soap,
horticultural oil Conventional pesticides: acephate, azadirachtin, bifenthrin, carbaryl, chlorpyrifos (nursery only), deltamethrin, imidacloprid. |
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Spruce
budworm References: IPM of Midwest Landscapes (UMN)
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Time: May, June
Hosts: Spruce The spruce budworm is one of the most destructive native insects in the northern spruce and fir forests of the Eastern United States and Canada. The first recorded outbreak of the spruce budworm in the United States occurred in Maine about 1807 and 1878. Since 1909 there have been waves of budworm out breaks throughout the Eastern United States and Canada. The States most often affected are Maine, New Hampshire, New York, Michigan, Minnesota, and Wisconsin. These outbreaks have resulted in the loss of millions of cords of spruce and fir. Balsam fir, white, red, and black spruce are suitable host trees and some feeding may occur on tamarack, pine, and hemlock. Spruce mixed with balsam fir is more likely to suffer budworm damage than spruce in pure stands. Use insecticides in May when larvae are feeding on needles before entering buds. Use BT, spinosad, acephate, bifenthrin, chlorpyrifos, carbaryl In the spring, after several days of warm weather, larva emerges from hibernation and begin feeding. Early feeding is first confined to the new buds of staminate flowers if present, or the larva mines the previous year's needles if staminate flowers are scarce. The new flower buds provide a ready source of food before the vegetative buds expand. The larva migrates to the end of a twig and bores into a needle or an expanding vegetative bud. When the larva is in the fifth instar, it begins tying the tips of twigs together with silk, forming a small nest. The new foliage is eaten first. In epidemic situations, old needles and bark (near branch tips) may also be consumed to such a degree that branch tips and terminal shoots are destroyed. During late June through mid-July, depending on the weather, the larva completes development and stops feeding. Adults emerge in July to lay eggs. Biorational pesticides: insecticidal soap, horticultural oil. Conventional pesticides: acephate, azadirachtin, bifenthrin, carbaryl, chlorpyrifos (nursery only), deltamethrin, imidacloprid. |
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Pine tortoise scale References:
IPM of Midwest Landscapes
(UMN) |
Time: May to June; late July to Sept Hosts: Jack, Scotch, and Virginia pine are preferred, but Austrian, mugo, red, slash, Swiss mountain, and white pine are also susceptible. Adult female scales are reddish brown. They are convex and 4 to 7 mm in diameter. Males are small, flat, and translucent. Flying adult males resemble gnats. Crawlers are mostly transparent and common on needles. Overwintering adults are found on twigs; young nymphs on foliage. Crawlers hatch in late June to early July. There is one generation a year. Mated females 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 from feeding damage, and dieback may occur. Injury most frequently occurs on seedlings and saplings, which can be killed in heavy infestations. Mature trees may also be damaged. In spring, look for female scales at the base of needles. In late June to early July, look for transparent crawlers that settle on needles. Look for ants, wasps, and flies which are attracted to honeydew produced by the scales. Also look for sooty mold growing on honeydew and for needle yellowing. To conserve beneficial insects, use short duration, low residual insecticides such as horticultural oil, insecticidal soap, and insect growth regulators (IGR).
Foliar applied broad spectrum insecticides, such as acephate, carbaryl, imidacloprid, and pyrethroids should only be used when scale populations are high--beneficial insects will be also killed.
Dormant season oil treatments may be used for soft scales that overwinter as immatures, and for armored scales that overwinter as eggs under female covers (delayed dormant).
Summer oil treatments will smother exposed eggs, crawlers, and immature females.
Insect growth regulators (IGR), such as pyriproxifen, disrupt molting and is used for crawlers.
Soil applied systemic insecticides or trunk injections, such as imidacloprid: Apply imidacloprid in fall for crawlers in spring; not effective against armored scales which feed at different sites than soft scales. Less harmful to beneficial insects than foliar-applied, broad spectrum insecticides. |
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Nursery and Greenhouse |
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Western flower thrips References: Western Flower Thrips in Commercial Greenhouses (UMN Extension) Western Flower Thrips Feeding Scars and Tospovirus Lesions on Petunia Indicator Plants Agdia DAS ELISA and ImmunoStrip test
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Time: All year in
GH
Hosts: Many
flowering plants The western flower thrips feeds on the flowers and foliage by inserting its modified left mandible into the tissue, and sucking the fluids from cells. Oviposition and feeding scars reduce the aesthetic quality and marketability of ornamental plants. When thrips feed on developing tissues, affected cells are unable to expand, and mature leaves and petals are distorted. When thrips feed on expanded tissue, effected cells become filled with air, which imparts a silvery appearance. These thrips spread tomato spotted wilt (TSWV) and impatiens necrotic spot viruses (INSV). Females lay eggs in tender plant tissue. The eggs hatch in 2 to 14 days, depending on temperature. First instar larvae begin feeding on egg eclosion. Second-instar larvae also feed on plant tissue, usually in flowers. These larvae are found in the protection of perianth of the flower or within developing terminal foliage. Late in the second instar they stop feeding and move down the plant to pupate. Thrips develop through two quiescent, non-feeding pupal stages in the soil, plant litter or in a protected area on the plant. Adults emerge and resume feeding on flowers, buds, and terminal foliage. The entire life cycle from oviposition to adult emergence can take 12 days in hot weather to 44 days in cool weather. Larvae: The larvae develop through two instars and are distinctly yellow. Second instars become whitish prior to molting. Prepupae and Pupae: Both prepupa and pupa are yellowish, quiescent non-feeding stages. The antennae and wing pads are typical for most thrips species. Pupae are found on soil and debris. Adults: Western flower thrips is about 1
mm long, with the female larger than the male. The female varies from yellow
to dark brown, and has a more rounded abdomen. The male is always pale yellow
and has a narrower abdomen. Management: Rotate classes of insecticides to prevent resistance.
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Greenhouse thrips References: |
Time: All year in
GH
Hosts: Many
flowering plants Greenhouse thrips move relatively slowly and rarely fly. They prefer a cool, shady, and fairly moist atmosphere. These thrips feed in colonies on the foliage and fruit. They select neither the youngest nor the oldest leaves on which to feed. Often the flowers/fruit is preferred to the leaves. Since males are not common, reproduction is usually by parthenogenesis (laying unfertilized eggs). Males were first found in 1940. Each female deposits 25 to 50 eggs in slits in the leaves. Under optimum conditions the time for development is 17 to 20 days for the eggs, about 13 days for the two larval instars, and about 5 days for the prepupal and pupal stages. The adults can live 7 weeks on plants growing in the greenhouse. All stages can be found throughout the year in greenhouses. Dark spots of excrement are often noticeable on the leaves and fruit. Larvae: The first larval instar is white; the second instar is yellow. Both instars have red eyes. Pupae and Prepupae: The pupa and prepupa do not move about freely. These stages are yellowish with red eyes. Pupae are slightly larger, with longer wing pads, and antennae bent back over body. They become darker with age. Pupae are found on leaves. Adults: The head and central area of the body have a distinct network of lines. The body is dark brown with the posterior end much lighter; the legs are uniformly yellow. Management: See western flower thrips. |
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Turf |
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European crane fly
Marsh crane fly (Diptera: Tipulidae) References:
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Time: Oct to Sept (larvae); Sept to Oct. (adults)
Hosts: Lawns,
nursery stock Crane flies are two-winged flies that are often mistaken for giant mosquitoes. The adults are harmless. The larvae of many crane flies are aquatic and their presence is an indicator of good water quality. Other crane flies are terrestrial decomposers and help break down decaying organic matter.
The crane fly known as the European crane fly in
the Pacific Northwest, Tipula paludosa Meigan, is an introduced exotic
pest first found in the region in 1965 in British Columbia, Canada. Since
then, it has gradually spread into
In
1998, a second, closely related crane fly species from Europe was found in the
In Washington and Oregon, crane fly larvae over-winter in lawns. Larger larvae can be found in the top three inches (3") of turf in spring. Infested grass may appear yellow or have dead spots. Adults emerge in late summer and early fall. As adults emerge, the leathery, shiny pupal cases (leatherjackets) are an indicator of where crane fly larvae were living and where the next eggs are most likely to hatch. The adults mate almost immediately after they emerge. The females lay most of their eggs before they make their first flights. At nurseries where leatherjackets are a chronic problem, susceptible stock should be drenched with an insecticide in October when young larvae are at their most susceptible stage. Sprays should be irrigated in to the top 5 cm of the soil or growing medium in the evening when leatherjackets come to the surface to browse. |
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Japanese beetle References: IPM of Midwest Landscapes (UMN)
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Time: May, June, July Hosts: Grubs on grass roots; adults on foliage Introduced in 1916 near Riverton, New Jersey. The Japanese beetle is a serious. Grubs feed on the roots of turf grass and adults feed on the foliage of more than 300 plant species. Grubs chew off grass roots and reduce the ability of grass to take up enough water to withstand stresses of hot, dry weather. As a result, large dead patches of grass develop in grub infested areas. The sod on these dead patches can be rolled back like a carpet to expose the grubs and the lack of turf roots. Early recognition of the problem can prevent this destruction. There are five small, white patches of short hairs along each side of the dorsal abdomen on the beetle. These patches are a key characteristic for identification Grub populations between 7 and 15 per square foot can cause significant damage to non-irrigated turf. Irrigated turf can withstand a higher grub count because the increase in water compensates for the roots chewed off by the grub. Timing of pesticide treatment is important. Treating grubs in the spring is also more difficult as they are bigger and do not feed for long before they pupate Larger grubs are more difficult to control with insecticides, and the grubs are difficult to kill in the fall because they are larger. In early July females emerge to lay eggs Life cycle of Japanese beetle: egg, grub, and adult stages. Imidacloprid (Merit) is not fast acting, so use as a preventative control, not as a rescue treatment. Apply imidacloprid between May 15 and August 30. Halofenzide an IGR (insect growth regulator) (Mach2, GrubEX) is not fast acting, but only use in June to August to control grubs. For adults, use pyrethroid insecticides such as bifenthrin. |
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