Saitama Prefecture Launches 'Great Survey of Red-necked Longhorn Beetle 2026'

The International Center for Environmental Science is launching the 'Great Survey of Red-necked Longhorn Beetle 2026' to assess damage caused by the invasive pest 'Red-necked Longhorn Beetle,' which kills cherry, plum, peach, and apricot trees, and to effectively promote control measures.

Since fiscal year 2018, this survey has been conducted to implement pest control in affected areas. However, the number of damaged sites continues to increase annually, and the affected regions are expanding.

To prevent new damage, we urge public participation in the survey and request cooperation in reporting sightings of adult beetles (Figure 1), which are active in summer, and frass (Figure 2—a mixture of feces and wood debris) expelled by larvae.

Figure 1: Red-necked Longhorn Beetle (male) Figure 2: Frass (brown, hard, candy-like pellets)

1. Survey Method (For details, refer to the 'Great Survey of Red-necked Longhorn Beetle Manual 2026')

(1) Survey Locations and Tree Species

The primary survey targets are cherry trees planted in parks, riverbanks, schools, and other locations within Saitama Prefecture. Please check for adult beetles and expelled frass. Cherry tree rows along rivers and roads are particularly prone to spreading damage and should be prioritized. Additionally, please also check for damage on other Rosaceae trees such as plum, peach, and apricot.

Information on locations with no damage is also important, so please confirm and report these as well.

(2) Reporting Methods

Please report your observations via a dedicated smartphone form, email, or postal mail. You may also report to your local municipality or the land/facility manager, who will then share the information with the International Center for Environmental Science.

Dedicated Form

Email: g7383316@pref.saitama.lg.jp

Mail: Biodiversity Center, International Center for Environmental Science, 914 Kamitaneashi, Kazo City, Saitama 347-0115

(3) Reporting Period

The intensive survey period runs from today until Monday, August 31, Reiwa 8 (2026). However, reports are accepted outside this period as well.

(4) Detailed Characteristics of the Red-necked Longhorn Beetle

Its natural distribution includes China, Mongolia, the Korean Peninsula, and Vietnam.

Adults are 25–40 mm in length, with a bright red 'neck' and a glossy black body (Figure 1).

Adults are active during the day and emit a citrus-like odor.

Females lay eggs in cracks in tree bark and can lay up to nearly 1,000 eggs, indicating extremely high reproductive capacity.

Larvae prefer to feed on living wood of Rosaceae trees such as cherry, plum, peach, and apricot.

Larvae are active from spring to autumn, during which they expel frass (Figure 2).

Larvae grow inside the tree for 2–3 years before pupating, emerging as adults from June to August.

The adult lifespan in the wild is approximately one month.

2. Other Information

The Red-necked Longhorn Beetle is designated as a 'Specified Invasive Alien Species' under Japan's Invasive Alien Species Act due to its significant impact on ecosystems. Rearing or transporting the beetle is strictly prohibited.

If you find an adult beetle, please capture and kill it immediately on site to prevent further spread. Note that the beetle does not sting and poses no danger to humans.

For more details on the survey, please visit the 'Red-necked Longhorn Beetle Information' website.

References

Results of the 'Great Survey of Red-necked Longhorn Beetle' in FY Reiwa 7

https://www.pref.saitama.lg.jp/b0508/news/page/news2026060801.html

Great Survey of Red-necked Longhorn Beetle Manual 2026

d104306-989-44dabd17047f471db75d40f83104f4bf.pdf