''Xyleborus monographus'', the Mediterranean oak borer, is a species of

ambrosia beetle Ambrosia beetles are beetles of the weevil subfamilies Scolytinae and Platypodinae (Coleoptera, Curculionidae), which live in nutritional symbiosis with ambrosia fungi. The beetles excavate tunnels in dead or stressed trees into which they introduc ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Curculionidae The Curculionidae are a family of weevils, commonly called snout beetles or true weevils. They are one of the largest animal families with 6,800 genera and 83,000 species described worldwide. They are the sister group to the family Brentidae. Th ...

. It is native to oaks in the regions around the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

, but since 2019 has been found in California, where the oak trees it infests may be more vulnerable.

Native habitat

The Mediterranean oak borer is around long. It is native to the regions surrounding the Mediterranean. In these parts of Europe, the Middle East and North Africa the beetle mostly infests dead and dying oak trees. It is found in at least twelve species of oak. As with other ambrosia beetles, it carries symbiotic

ambrosia fungi Ambrosia fungi are Fungus, fungal symbionts of ambrosia beetles including the polyphagous shot hole borer, polyphagous and Kuroshio shot hole borers. There are a few dozen species described ambrosia fungi, currently placed in polyphyletic genera '' ...

, which it cultivates for food along the boring tunnels. One of these fungi, ''Raffaelea montetyi'', seems linked to

wilt disease A wilt disease is any number of diseases that affect the vascular system of plants. Attacks by fungi, bacteria, and nematodes can cause rapid killing of plants, large tree branches or even entire trees. Wilt diseases in woody plants tend to fal ...

in cork trees (''

Quercus suber ''Quercus suber'', commonly called the cork oak, is a medium-sized, evergreen oak tree in the section ''Quercus'' sect. ''Cerris''. It is the primary source of cork for wine bottle stoppers and other uses, such as cork flooring and as the core ...

'') in Portugal. When the females fly to another tree they carry the fungal spores in their mycangia. The beetle penetrates through thin or cracked bark in the canopy branches. It first invades and kill branches in the canopy of a tree, then spreads to the trunk, culminating in the death of the tree. The females produce two or more generations annually. Large populations can develop in the lower trunk over a number of growing seasons. The fungi take nutrients from the

xylem Xylem is one of the two types of transport tissue (biology), tissue in vascular plants, the other being phloem; both of these are part of the vascular bundle. The basic function of the xylem is to transport water upward from the roots to parts o ...

, which transports nutrients from the roots of the tree to its stems and leaves. Mechanical damage seems to cause the greatest amount of damage, since the extensive tunnels weaken the tree limbs, which may break.

California invasion

The Mediterranean oak borer probably reached California around 2015. It was found in 2019 in

Napa County Napa County () is a County (United States), county north of San Pablo Bay located in the Northern California, northern portion of the U.S. state of California. As of the 2020 United States census, the population was 138,019. The county seat i ...

, infesting oak trees near Calistoga. Since then it has been found in Lake County,

Sonoma County Sonoma County ( ) is a county located in the U.S. state of California. As of the 2020 United States census, its population was 488,863. Its seat of government and largest city is Santa Rosa. Sonoma County comprises the Santa Rosa-Petaluma ...

and suburbs of

Sacramento Sacramento ( or ; ; ) is the capital city of the U.S. state of California and the seat of Sacramento County. Located at the confluence of the Sacramento and American Rivers in Northern California's Sacramento Valley, Sacramento's 2020 p ...

. It is not clear whether healthy trees are vulnerable, since the valley oak ('' Quercus lobata'') and blue oak (''

Quercus douglasii ''Quercus douglasii'', known as blue oak, is a species of oak endemic to California, common in the Coast Ranges and the foothills of the Sierra Nevada. It is California's most drought-tolerant deciduous oak, and is a dominant species in the b ...

'') trees that were infested by Mediterranean Oak Borers were already under stress from other factors. As of August 2020 the

California Department of Food and Agriculture The California Department of Food and Agriculture (CDFA) is a Cabinet (government), cabinet-level agency in the government of California. Established in 1919 by the California State Legislature and signed into law by Governor William Stephens (Am ...

was cooperating with county, state and federal organizations to survey the patterns of infestation and investigate approaches to managing the beetle.

References

Sources

* * * * {{Taxonbar, from=Q19796593 Scolytinae Beetles described in 1792