A pest that leaves unsightly ‘sugar volcanoes’ is trashing Calif. home values

The California Department of Food and Agriculture has released a lengthy analysis to address the “rising tide” of invasive pests entering the state — and according to the report, one seed-sized beetle is ravaging California’s landscape and likely costing billions of dollars in damages as a result. 

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The tiny but destructive invasive shot-hole borer poses an “imminent threat” to urban forests and home values throughout Southern California, particularly in Los Angeles County, interactive maps show. The two predominant species, the Kuroshio shot-hole borer and polyphagous shot-hole borer, are known to take over 60 different tree species in the state, and in 2024, a third species of ISHB was discovered as far north as Santa Cruz County. 

The flying beetle, which carries a fungal pathogen that leads to a disease called Fusarium dieback, destroyed 120,000 willows in within just three years, a 2019 study found. After females spread the symbiotic fungus by boring into trunks and branches, the fungus blocks water from moving through the tree’s vascular system, ultimately killing it. Though pocks and stains are common symptoms among infected hosts, the fungus can also cause unsightly “sugar volcanoes” to appear on avocado trees. 

According to an informational video posted by University of California Agriculture and Natural Resources, ISHBs are well established in Southern California and spreading to other parts of the state. A UCANR map also shows that the presence of these beetles has been confirmed in some of Southern California’s wealthiest ZIP codes: 90210 and 90402. 

Already “it has affected home values in areas where it has become established and caused tree death,” Karen Jetter, an author in the CDFA analysis and UC ANR Policy Institute associate director, told SFGATE in an email Tuesday, adding that the invasive pests pose a threat to property values virtually everywhere in California except for areas at very high elevations. According to Jetter, “significant research” shows that “nicely landscaped environments result in higher property values on average.” The Arbor Day Foundation estimates that planting large trees on properties can increase their value between 3% and 15%.  

In urban areas, tree cover provides vast benefits for homeowners: It e,” a 2021 report from the University of Nebraska said. In 2017, tree cover alone increased the value of private homes in the U.S. by $604.2 billion, the report said. 

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Acording to the new CDFA analysis, ISHBs  are capable of killing up to 40% of their hosts. To make matters more complicated, researchers in San Diego say that “because so little is known about the ecology of the borers, it has been impossible to explain their current patterns of distribution and impact, or to predict where they will impact next.”

“Over the past three decades, the scale and complexity of pest threats have increased dramatically,” Lindsey Carter, executive director of the California Agricultural Commissioners and Sealers Association, said in an April 30 CDFA release. “The return on investment for pest prevention is already high, but when you factor in the potential losses – not just to agriculture, but to natural ecosystems and urban environments – the case for increased funding becomes overwhelming.”  

While several programs are being used to combat the entry of pests in the state, the April report said, agencies recommend bolstering pay and increasing budgets. According to the release, California officials had to combat seven fruit fly infestations in 2023 and 2024, which cost $208 million and stretched the state’s pest prevention system to its “fullest capacity.”

“These pests are generally thought of as threats to agriculture, but it’s important to note that most of the infestations that happen in California happen in urban and suburban areas,” CDFA press representative Jay Van Rein told SFGATE Wednesday. “That’s because a major pathway for these pests to arrive here is when a traveler returns from overseas and unknowingly brings back pests inside of fruit, vegetables or other plant materials.” Van Rein added that these pests are the biggest threat to agriculture. However, early detections have usually helped the agency eradicate infestations before they move beyond urban areas.