Invasive Shot Hole Borers (ISHB) (Part III)

Invasive Shot Hole Borers (ISHB) (Part III)

Where do we monitor for SHB?

When looking for a host tree, the shot hole borers prefer live, healthy trees, unlike most ambrosia beetles that prefer stressed or dying trees. And they also prefer well-irrigated trees, which includes riparian trees. The polyphagous shot hole borer has been detected in 342 tree and woody plant species in CA, including agricultural, riparian and urban trees. Currently, there are 64 confirmed species of trees in which the beetles can successfully grow their fungus and complete their life cycle. 

Susceptible trees include many of the species commonly used for landscaping; like 

• sycamores
• oaks
• cottonwoods
• box elder
• willows  
• maples
• castor bean (preferred host, not a tree)
• many others 

Shot hole borers can also infect Avocado, but growers can manage infestations by using best management practices.To find the full list of ISHB reproductive hosts (including the canker-associated hosts) please visit pshb.org.

White powdery exudate (sugar volcanoes) are a common symptom of ISHB infestation in avocado trees. (Credit: Monica Dimson, UCCE Orange Co.)

Trunk of a heavily infested California sycamore (Platanus racemosa). Note the staining around each ISHB entry hole. (Credit: Beatriz Nobua-Behrmann)

Lindgren Traps or Bottle Traps with a Quercivorol lure are used to monitor and trap shot hole borers. Lures can be purchased from UCSB. 

Standard shot hole borer Lindgren trap.

Invasive Shot Hole Borers (ISHB) (Part II)

Invasive Shot Hole Borers (ISHB) (Part II)

When the beetles bore into a tree, they create a series of tunnels where they farm the fungus and produce young. This series of tunnels is referred to as a gallery. Their winding galleries can reach to a depth of around 3 inches (8 cm) into the tree's wood. The dark stains in the wood is caused by the fungus (Fusarium euwallaceae), which not only causes the beetle's galleries to be stained black, but also moves into the tree's xylem, clogging it. The clogged xylem will prevent the tree from distributing water and nutrients and leads to branch dieback and the eventual death of the tree.

The Fusarium can also cause a sugary exudate (also called a sugar volcano) and gumming.  While inspecting trees you may also see the beetle entry & exit holes (about 0.85 mm or the size of pen head in diameter) and sometimes you can see the abdomen of a female beetle sticking out of the hole.

Fusarium in the gallery and branch dieback in oak.

Beetles and Galleries in the wood.

An infected Sycamore tree that was removed due to potential fire hazard and property destruction in Montecito.

Invasive Shot Hole Borers (ISHB) (Part I)

Invasive Shot Hole Borers (ISHB) (Part I)

There are two types of Invasive Shot Hole Borers that we are concerned about in Santa Barbara County; the Polyphagous Shot Hole Borer and the Kuroshio Shot Hole Borer. The two beetles look the same, but are genetically different and can be identified using DNA analysis. Both shot hole borers are a group of ambrosia beetles that make tiny entry holes in trees.They are ambrosia beetles because they carry a symbiotic fungus with them. The fungus (Fusarium spp.) is carried along by female in special organs in her mouth parts and is used to infest the host plant.  The beetles farm the fungus and both adult beetles and larvae feed on fungus. A mated female will find a suitable host and bore into it to create galleries (a series of tunnels) to farm the fungus and lay her eggs.  These shot hole borers infest healthy trees, but the fungus causes the tree to die slowly by clogging its vascular system and preventing the movement of water and nutrients.  Once the tree can no longer sustain fungal growth, the beetles will fly to a new host.  They spend a majority of their lives within the galleries inside the tree (this makes it very difficult to control the beetles). 

The female (a) is darker and slightly larger than the male (b).

A Rise in HLB Detections

Detections of Huanglongbing (HLB), the causal agent of the incurable citrus greening disease, have risen significantly in 2018 compared to the previous years. A reason for the rise in finds can be attributed to improved sampling and monitoring methods.  In 2018, the California Department of Food and Agriculture’s (CDFA) Citrus Pest and Disease Prevention Program (CPDPP) redoubled efforts to limit the spread of HLB and its vector. HLB is spread by a small pest called the Asian citrus psyllid (ACP) as it feeds on citrus tree leaves. The disease is fatal for citrus trees and has no cure. Once a tree is confirmed with the disease, the California Department of Food and Agriculture (CDFA) removes the infected tree from the property in order to protect neighboring citrus trees.

HLB was detected in 269 trees in 2017 and 699 trees in 2018, with a majority of these occurring in Los Angeles and Orange counties. The disease was first discovered in in Hacienda Heights, California, in 2012. The disease has not yet been detected in a California commercial grove, though most industry experts believe it’s just a matter of time.

One of the means of limiting the spread of HLB is implementing quarantines when ACP is discovered. ACP quarantines are already in place in 27 counties (including Santa Barbara County) in the state.  Information regarding quarantine zones and protocols is available through the CPDPP website. The quarantines throughout the state limit the transport of citrus across state and international lines, and between areas where the psyllid and disease have been found. Additionally, CDFA has agriculture crews canvassing the state to inspect backyard citrus trees for the Asian citrus psyllid and HLB.

Adult Asian Citrus Psyllid (ACP) feeding on citrus.  Photo-UCCE.

Gold Spotted Oak Borer

The goldspotted oak borer (GSOB), Agrilus auroguttatus is a flat headed borer that poses a significant threat to oak trees. The pest is native to southeastern Arizona and was first identified in California in 2004 in San Diego County. It has since been killing trees throughout San Diego, Los Angeles, and Orange Counties in forests, parks, and residential landscapes.

GSOB larvae feed beneath the bark near the vascular tissue in the older, mature trees.  Trees die after several years of injury inflicted by multiple generations of the beetle, causing significant economic, ecological, cultural, and aesthetic losses to the region. GSOB poses a major threat to susceptible oak species (Coast Live Oak, Canyon Live Oak, and California Black Oak) throughout California and southern Oregon. Currently there are no effective tools for protecting trees once infestation occurs.

We have placed GSOB traps, in accordance with USDA and CDFA, throughout Santa Barbara county focusing on placing them in campgrounds where infected firewood may introduce GSOB. Our hope is that if any GSOB are in our county, that the traps will catch them during the flight season May-September. More info can be found here: http://ucanr.edu/sites/gsobinfo/

Mature GSOB to scale.  Photo UC Cooperative Extension.

Lateral view of GSOB.  Photo CISR- Center for Invasive Species Research, UC Riverside.

D-shaped  exit holes (3-4 mm).  Photo UC Cooperative Extension.

Live Oak being removed after succumbing to GSOB in Southern CA.  Photo CISR- Center for Invasive Species Research, UC Riverside.

 GSOB trap placed in Santa Barbara County for the 2019 trapping season.  Photo-Mel Graham, Santa Barbara County Ag Commissioner's Office.

Lookout for Spotted Lanternfly

An exotic pest known as the spotted lanternfly, Lycorma delicatula (White), is native to China and was first detected in Pennsylvania in September 2014. It has not yet arrived in California, but has been spreading rapidly across the eastern US. 

Spotted lanternfly is actually not a fly, but a planthopper and is also referred to as “spot clothing wax cicada” or “Chinese blistering cicada”. This species is significant because the spotted lanternfly feeds on more than 70 host species including a wide range of fruit, ornamental and woody trees, with tree-of-heaven being one of the preferred hosts. Spotted lanternflies are invasive and can be spread long distances by people who move infested material or items containing egg masses.

If allowed to spread in the United States, this pest could seriously impact the country’s grape, walnuts, avocados, and pistachios, and logging industries. The California Department of Food and Agriculture has awarded funding for one project to develop biological control agents to help manage the spread of the spotted lanternfly.

To prevent the spread of the spotted lanternfly, carefully inspect potential sources such as woody plant debris, yard waste, plants, or other objects.  Destroy or disinfest the sources as appropriate to prevent the spread of the pest.

Detailed information on this pest can be found here: https://www.aphis.usda.gov/aphis/resources/pests-diseases/hungry-pests/the-threat/spotted-lanternfly/spotted-lanternfly

Lateral view of a resting adult spotted lanternfly. Photo Credit: Lawrence Barringer.

Dorsal view of an adult female spotted lanternfly. The colorful hindwings and the black and yellow abdomen are not visible at rest. Photo Credit: Lawrence Barringer.

Fourth instar nymph of the spotted lanternfly. Photo by Lawrence Barringer, Pennsylvania Department of Agriculture.

Adult spotted lanternfly infestations.  Photo by Lawrence Barringer, Pennsylvania Department of Agriculture.

Welcome to the Santa Barbara County IPM Blog!

This is our first ever post!  What a great way to help share information with Santa Barbara County growers.  Our hope it that we can share up-to-date information about pest pressures, current issues, management options, research, and more with you.  Please comment if there are specific topics that you would like more information about.😃