Dendroctonus adjunctus

Last updated

Contents

Dendroctonus adjunctus
Roundheaded Pine Beetle (Dendroctonus adjunctus) adult.jpg
Adult Roundheaded Pine Beetle
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Infraorder: Cucujiformia
Family: Curculionidae
Genus: Dendroctonus
Species:
D. adjunctus
Binomial name
Dendroctonus adjunctus
Blandford, 1897

Dendroctonus adjunctus, the roundheaded pine beetle, is a species of bark beetle in the family Curculionidae found in North America. [1] [2] [3] A parasite, the roundheaded pine beetle feeds on and eventually kills pine trees of several species in Guatemala, Mexico, and the Southern United States (New Mexico, Arizona, Nevada, Colorado, Utah). [4] [5]

Roundheaded pine beetles are a serious threat to wild and commercial pine stocks, wiping out up to half of pine trees in a region in outbreak years. To prevent and mitigate the beetle's epidemic outbreaks, loggers have developed a variety of biological, cultural, and chemical controls. [4]

Description

Like many insect species, the roundheaded pine beetle goes through several stages in its life cycle, changing dramatically in appearance between each one. Adults are 5-6 mm long and 3 mm wide, with females slightly larger than males. Adult exoskeletons are shiny, reflective, dark brown or black, and covered with hairs. Their eyes are flat, don't protrude from the exoskeleton, and are generally elongated. The adult beetles have antennae and wings and can fly. [4] [6]

The roundheaded pine beetle's eggs, less than 1.5 mm in length and width, are much smaller than adults. They are oblong and pearly white. [4]

Larvae are C-shaped, legless, and mostly translucent, though their abdomens are sometimes visible as tinges of reddish-brown. Depending on the instar stage, the larvae's size can vary from slightly larger than an egg to slightly smaller than an adult. [4]

When the larvae become pupae, they become opaque white. The pupae also have antennae, legs, and wing covers, reflecting characteristics of the species' adult form. [4]

Life cycle

The lifespan of most roundheaded pine beetle is one year. In October and November, female adults gain flying abilities and colonize weakened pine trees by attacking the tree bole's basal portion. The beetles often capitalize on trees already attacked by species in the Ips and Dendroctonus genera. [4] Once they locate a desirable pine tree, they release aggregation pheromones, which attract other beetles to the tree. The beetles then bore through the pine's bark, constructing chambers where mating occurs. After mating, each male-female beetle pair works together to build egg galleries, carving grid-like structures of tunnels where females lay and store their eggs. Though egg galleries of different mating pairs often cross, it appears roundheaded pine beetles do not actively cooperate in infesting trees beyond male-female mating partnerships. [4] [7]

The roundheaded pine beetle's egg galleries can grow to be pretty extensive, as each horizontal tunnel is on average separated by 2.5-5 cm and each longitudinal tunnel by 30 cm. Each gallery overall is usually 30.5 cm long, but large galleries can extend to 1.2 meters. Female roundheaded pine beetles fill their galleries with egg, depositing one egg per grid niche on alternating sides of the gallery. [4] [7] The beetles initially keep the egg gallery free of dust, but as the gallery deepens into the tree, male beetles packs the first few inches of tunnels closest to the pine bark with boring dust, probably to protect the eggs. [4]

Beneath the bark, these egg galleries mostly exist in the tree's cambium, the layer separating the pine's xylem, transport tissue carrying water from tree roots to leaves, from its phloem, tissue ferrying sugar and other nutrients around the plant. However, the egg galleries extend into the tree's phloem and often its xylem as well extend beyond; the roundheaded pine beetles coopt phloem into their habitat, severing the tree's internal circulation and drastically reducing its ability to get sugars and nutrients to where they're needed. Roundheaded pine beetle pairs also feed on phloem throughout, further sapping the host tree of nutrients. [4] [5]

Roundheaded pine beetle pairs that begin boring into trees in October complete their galleries by December; those that start in November can only partially complete their dwellings by December. For these beetles, cold bark temperatures between December and February limits their gallery tunneling to the few days when the bark is warm enough for activity. Adult roundheaded beetles continue a minor amount of construction in March and April. [4]

Roundheaded eggs generally hatch between mid-March and late April; the eggs of beetle pairs that colonized pines in October may hatch in the winter, but almost all quickly perish from cold. Though early-hatching eggs die, unhatched beetles are surprisingly resilient against the winter cold, surviving in temperatures as low as -25°F. [4] Young larvae form small feeding galleries in the phloem. After their first molt, the larvae bore outwards, mining the tree's cambium; after their second molt, in the third instar phase, the young roundheaded pine beetles tunnel into the outer bark to complete their development. [7] As they excavate, the beetles broaden a series of feeding channels leading to what will become pupal chambers, laying the groundwork for the pine beetles to more easily pupate into adult form. [4]

The roundheaded larvae rapidly develop through the third instar phase, molting to reach the fourth instar. Fourth-instar larvae mature much more slowly, generally only pupating into adults in late July and early August. In fringe cases, however, beetles may pupate as early as June and as late as mid-September. Once adults, the roundheaded pine beetles remain in their sickening host pine of birth for 2 to 3 months, departing between late September and early November. [4] By late November, adults will have located fresh pines to colonize, mate in, and build an egg gallery, thus restarting the cycle.

Effects on trees and outbreaks

By using pine tree's phloem for food, habitat, and egg-laying, roundheaded pine beetles are extremely destructive towards pines, as they sever the tree's circulation, sap it of nutrients, and eliminate its ability to get sugar to where it's needed. [5] The beetles can kill individual trees, clumps of dozens of pines, and even wipe out pines from entire forests. In the US, roundheaded beetles target and kill young, mature, and overmature Pinus ponderosa pines. They particularly thrive when pole-sized ponderosa pines are tightly packed together; each tree is large enough to support the beetles, while the pines' close proximity allows the beetles to easily fly from one tree to the next, infecting all. [4]

Periodic outbreaks, while brief and infrequent, are devastating to ponderosa pine populations. In 1950, roundheaded pine beetles infested 16,000 pole-sized ponderosa pines near Cloudcroft, New Mexico. In 1971, an even more devastating epidemic occurred, as the species killed 400,000 pole-sized ponderosas in southern New Mexico. In the 1990s, the roundheaded beetles caused similar epidemics of pine tree death in the mountains of southern New Mexico and southeastern Arizona. [7]

In dense clumps, the beetles colonize and kill pines in groups of 3 to 15; in exceptional cases, they wipe out up to 100 trees at a time. Roundheaded pine beetles can kill up to 50% of the trees in pure ponderosa pine stands; even when pines are interspersed with other conifers, roundheaded beetles still eliminate up to 50% of pines, in doing so reshaping forest ecosystems by leaving Douglas firs as the dominant species.

While attacking ponderosa pines the most, roundheaded pine beetles also colonize and kill the limber pine in the United States. In Mexico and Guatemala, the roundheaded beetle also attacks the Mexican white pine, Chihuahua pine, Montezuma pine, and Pinus pseudostrobus . [4]

Roundheaded pine beetles also spreads the fungi Ophiostoma adjuncti and Leptographium pyrinum as it infects trees. The role these fungi play in benefitting the beetle or killing the pines remains unclear. [5]

Predators and parasites

The red-bellied cleric and a predacious beetle Temnochila virescens prey on roundheaded beetles, while braconid wasps of the Coleoides genus and the nematodes Parasitylenchus stipatus and Parasitylenchus dendroctoni parasitize roundheaded beetles. The latter two nematode species are used to target egg-laying adult females, as the parasites sap the beetles of resources, halving egg production of invested females. Woodpeckers are also closely associated with roundheaded pine beetles; given that they consume over 90% of other species in the Dendroctonus genus on individual trees, they likely also heavily predate on roundheaded beetles. [4]

Pest control

Given the deleterious effects roundheaded pine beetles have on commercial and wild pine populations, the United States Forest Service recommends combining biological, cultural, and chemical control to mitigate roundheaded populations before the beetles' infestations become epidemic. [4] The Forest Service recommends using natural predators and parasites to control the beetles. Commercial landowners can also culturally adapt to roundheaded pine beetle infestations by thinning their forest stocks and felling and burning infested pines as soon as possible. Chemically controlling roundheaded beetles requires lots of time and resources, so it is generally limited to protect pine trees of the highest value. [4]

Related Research Articles

<span class="mw-page-title-main">Telephone-pole beetle</span> Species of beetle

The telephone-pole beetle is a beetle native to the eastern United States and the only living representative of the otherwise extinct family Micromalthidae. Larvae of the beetle live in decaying wood and can be pests to wooden structures, lending them their common name, the 'telephone-pole beetle.'

<span class="mw-page-title-main">Emerald ash borer</span> Species of beetle

The emerald ash borer, also known by the acronym EAB, is a green buprestid or jewel beetle native to north-eastern Asia that feeds on ash species. Females lay eggs in bark crevices on ash trees, and larvae feed underneath the bark of ash trees to emerge as adults in one to two years. In its native range, it is typically found at low densities and does not cause significant damage to trees native to the area. Outside its native range, it is an invasive species and is highly destructive to ash trees native to Europe and North America. Before it was found in North America, very little was known about emerald ash borer in its native range; this has resulted in much of the research on its biology being focused in North America. Local governments in North America are attempting to control it by monitoring its spread, diversifying tree species, and through the use of insecticides and biological control.

<span class="mw-page-title-main">Bark beetle</span> Subfamily of beetles

A bark beetle is the common name for the subfamily of beetles Scolytinae. Previously, this was considered a distinct family (Scolytidae), but is now understood to be a specialized clade of the "true weevil" family (Curculionidae). Although the term "bark beetle" refers to the fact that many species feed in the inner bark (phloem) layer of trees, the subfamily also has many species with other lifestyles, including some that bore into wood, feed in fruit and seeds, or tunnel into herbaceous plants. Well-known species are members of the type genus Scolytus, namely the European elm bark beetle S. multistriatus and the large elm bark beetle S. scolytus, which like the American elm bark beetle Hylurgopinus rufipes, transmit Dutch elm disease fungi (Ophiostoma). The mountain pine beetle Dendroctonus ponderosae, southern pine beetle Dendroctonus frontalis, and their near relatives are major pests of conifer forests in North America. A similarly aggressive species in Europe is the spruce ips Ips typographus. A tiny bark beetle, the coffee berry borer, Hypothenemus hampei is a major pest on coffee plantations around the world.

<span class="mw-page-title-main">Mountain pine beetle</span> Species of beetle

The mountain pine beetle is a species of bark beetle native to the forests of western North America from Mexico to central British Columbia. It has a hard black exoskeleton, and measures approximately 5 millimetres, about the size of a grain of rice.

<i>Thanasimus formicarius</i> Species of beetle

The ant beetle, also known as the European red-bellied clerid, is a medium size insect, rather soft-bodied, with strong mandibles that can tear between the hard sclerotized integument of bark beetles. Larvae and adults are common predators of bark beetles in Europe.

<i>Tomicus piniperda</i> Species of beetle

Tomicus piniperda, the common pine shoot beetle, is a bark beetle native throughout Europe, northwestern Africa, and northern Asia. It is one of the most destructive shoot-feeding species in northern Europe.

<i>Dendroctonus</i> Genus of beetles

Dendroctonus is a genus of bark beetles. It includes several species notorious for destroying trees in the forests of North America. The genus has a symbiotic relationship with many different yeasts, particularly those in the genera Candida and Pichia that aid in digestion and pheromone production.

<i>Dendroctonus rufipennis</i> Species of beetle

Dendroctonus rufipennis, the spruce beetle, is a species of bark beetle native to British Columbia, Newfoundland and Labrador, Nova Scotia, Ontario, Quebec, Northern Manitoba, the Yukon, Alaska, Colorado, Wyoming, Montana, and Maine. They are known to destroy forests of spruce trees including Engelmann, White, Sitka, and Colorado blue spruce. Adults average 4 to 7 mm in length.

<i>Dendroctonus frontalis</i> Species of beetle

Dendroctonus frontalis, the southern pine beetle, often shortened to simply SPB, is a species of bark beetle native to the forests of the southern United States, Mexico and Central America. It has recently expanded its range to the northeastern United States, where it is considered an invasive species and has destroyed massive amounts of pine forest.

<i>Hylastes ater</i> Species of beetle

Hylastes ater is a species of beetle in the family Curculionidae, the true weevils. It is a bark beetle, a member of the subfamily Scolytinae. Its common name is the black pine bark beetle. It is native to Europe and parts of Asia, including China and Korea. It is known as an introduced species in many other regions, including Australia, New Zealand, the Americas, and South Africa. It is a pest of pines and other trees, and it is widespread in areas where pine trees are cultivated. The species "is an important threat to the biosecurity of all forested countries."

<i>Ips</i> (beetle) Genus of beetles

Ips is a genus of beetles in the family Curculionidae, the true weevils. They are bark beetles, members of the subfamily Scolytinae. Species are distributed throughout the Northern Hemisphere. Some are known as introduced species in Australia and Africa. Many species are pests of forest trees, especially pines and spruces. They are known commonly as engraver beetles, ips engraver beetles, and pine engravers.

<i>Platypus cylindrus</i> Species of beetle

Platypus cylindrus, commonly known as the oak pinhole borer, is a species of ambrosia beetle in the weevil family Scolytinae. The adults and larvae burrow under the bark of mature oak trees. It is native to Europe.

<i>Dendroctonus valens</i> Species of beetle

Dendroctonus valens, also known as the red turpentine beetle, is a species of bark beetle characterized by a dark-reddish brown hue. It is native to forests across North and Central America. In its adult form, these beetles range from six to ten millimeters in length. A notable characteristic about them is their use of acoustic signals and chemical cues when engaging in what is a very complex mating process.

<i>Dendroctonus micans</i> Species of beetle

Dendroctonus micans, the great spruce bark beetle, is a species of bark beetle native to the coniferous forests of Europe and Asia. The beetles burrow into the bark of spruce trees and lay eggs which develop into larvae that feed on the woody layers under the bark.

<i>Dendroctonus terebrans</i> Species of beetle

Dendroctonus terebrans, the black turpentine beetle, is a species of bark beetle native to the eastern United States. Its larvae tunnel under the bark of pine trees, weakening and sometimes killing the trees.

<i>Ips confusus</i> Species of beetle

Ips confusus, known generally as the pinyon pine beetle or pinyon ips, is a species of typical bark beetle in the family Curculionidae. It is found in Central America and North America.

<i>Dendroctonus brevicomis</i> Species of beetle

Dendroctonus brevicomis, the western pine beetle, is a species of crenulate bark beetle in the family Curculionidae. It is found in North America and parts of Mexico. It is known as a destructive pest of ponderosa and Coulter pine trees. When drought makes these pines more susceptible to infestations by D. brevicomis, there is an increased risk of forest fires due to dead trees.

<i>Pissodes nemorensis</i> Species of beetle

Pissodes nemorensis, known generally as the eastern pine weevil or deodar weevil, is a species of true weevil in the beetle family Curculionidae. It is found in North America and Africa. Deodar weevils are considered a forest pest in the United States, with adults and larvae feeding on a variety of coniferous tree species, including trees such as deodar cedar, loblolly pine, longleaf pine, sand pine, shortleaf pine, slash pine, and spruce pine Trees of all ages are susceptible to weevil infestations, while trees that are severely stressed by fire, drought, extreme cold, fusiform rust, wind damage, and other problems are prone to weevil infestation. In well-managed pine stands, deodar weevil infestations are sporadic, attacking only the suppressed and unhealthy trees throughout the area. Because they do not typically effect healthy trees, they do not usually alter traditional management strategies. Unlike many other forest pests in the eastern United States, deodar weevils are most active in the winter months, and this is often when sign of infestations can be seen. The best way to avoid a deodar weevil infestation is to maintain good tree and stand health: healthy trees do not typically face mortality or extensive damage from these pests. If an infestation has occurred, pesticides can be used in the fall as the weevils become active, but are typically not recommended.

<i>Ips pini</i> Species of beetle

Ips pini, also known as the pine engraver or North American pine engraver, is a species of typical bark beetle in the family Curculionidae found primarily in North America. These beetles are subcategorized by the distinctive geographic ranges in which they are found. A key distinguishing feature of different populations is how they produce the enantiomeric composition of ipsdienol, the major pheromone produced by males of this species.

Platypus quercivorus, the oak ambrosia beetle, is a species of weevil and pest of broad-leaved trees. This species is most commonly known for vectoring the fungus responsible for excessive oak dieback in Japan since the 1980s. It is found in Japan, India, Indonesia, New Guinea, and Taiwan.

References

  1. "Dendroctonus adjunctus Report". Integrated Taxonomic Information System. Retrieved 2019-09-24.
  2. "Dendroctonus adjunctus". GBIF. Retrieved 2019-09-24.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Darren Blackford (May 2004). "Management Guide for Roundheaded Pine Beetle" (PDF). US Forest Service.
  4. 1 2 3 4 Negron, Jose F. (2008). "Roundheaded Pine Beetle, Dendroctonus adjunctus". Encyclopedia of Entomology. Springer. doi:10.1007/978-1-4020-6359-6_3452 . Retrieved September 4, 2021.
  5. "Round-headed pine beetle: Diagnostic notes". Pest and Disease Image Library, Australian Government. August 6, 2003. Retrieved September 4, 2021.
  6. 1 2 3 4 "Field Guide to Insects and Diseases of Arizona and New Mexico Forests: Bark Beetles, Roundheaded Pine Beetle". US Forest Service. Retrieved September 4, 2021.

Further reading