Each year, the Nebraska Department of Agriculture (NDA) surveys for Japanese beetle (Popillia japonica) across the state. Following the 2016 survey season, NDA declared several additional counties as infested (Figure 1).

The Japanese beetle (JB) is a highly destructive insect. The grubs feed on plant roots while the adults feed on plant foliage and flowers. While landscape plants such as roses and linden are preferred hosts, the host list for this insect is extensive, including corn and soybeans.

The NDA is tasked with enforcing the Nebraska Plant Protection & Plant Pest Act which includes monitoring for invasive, exotic, and regulatory plant pests that may negatively impact plant industries. Regulatory pests, including the Japanese beetle, typically are identified under state and/or federal regulations or quarantines. The movement of specific regulated articles (i.e., nursery stock, firewood, Christmas trees, soil, etc.) is impacted by those regulations. The intent is to prevent the introduction and establishment of the regulatory pest in non-infested areas.

Nebraska regulates the Japanese beetle based on the U.S. Domestic Japanese Beetle Harmonization Plan (JBHP), and is considered a category 2 state under the plan. This identifies Nebraska as a partially infested state.

Nursery stock is one way pests like the Japanese beetle move from infested to non-infested places. Nursery stock shipped into Nebraska must adhere to state law, requiring it to be inspected and found apparently free of injurious plant pests. It must also be certified to meet the shipping requirements for category 2 states identified in the JBHP.

In order to maintain our Category 2 status, NDA must conduct an annual survey for Japanese beetles. If NDA stopped conducting these surveys, the state designation would default to Category 3, or generally infested. That would negatively impact those producers in non-infested areas of Nebraska that ship out of state. It also would mean nursery stock shipped into the state from infested areas wouldn’t require the additional certification step for Japanese beetle.

NDA Entomology staff conduct inspections of nursery stock entering the state to ensure it meets these requirements. Nebraska-grown stock is also inspected and certified, which includes inspecting for Japanese beetle.

Nebraska-grown nursery stock shipped to other states must meet the entry requirements of the receiving state. Nursery stock typically must (at a minimum) receive a visual inspection and be certified as apparently free from injurious plant pests. If the nursery stock originates in a Japanese beetle-infested county in Nebraska, it may also need to be certified as free from Japanese beetle. While most states follow the JBHP, some states have enacted individual quarantines with different requirements.  Therefore, the specific certification measures used vary depending on the nursery stock being shipped and the destination state. 

The certification process may include trapping, participation in a Containerized Accreditation program, application of approved chemical treatments, production in an approved greenhouse designated free of Japanese beetles, or production outside the adult flight period. NDA determines which certification method is appropriate for the specific situation and conducts the necessary inspections, surveys, or monitoring of activities necessary to meet the entry requirements of the receiving state. 

NDA has set and monitored Japanese beetle traps across the state for decades. The traps are yellow and green plastic, hung on a pole, and baited with a dual lure (food scent and pheromone). The traps are in place prior to June 1 and remain up until October 1. 

Nebraska was considered generally free of Japanese beetles until relatively recently. However, around 2000 a number of Japanese beetles were trapped across the Lincoln and Omaha areas. Since then, there has been a progression of what appear to be low-level infestations in the major population areas in the state. The beetle-infested counties follow along I-80 to the west and include the larger towns in the eastern third of Nebraska. Beetles have been caught in other counties not yet considered infested, but subsequent trapping/regulatory activities did not indicate the presence of an overwintering, established population.   

Typically if a single beetle is found in a trap, NDA will trap that county heavier the next year to determine if a population is established. Once an established population is confirmed, the county is considered infested. This is important for the certification of nursery stock that may be shipped interstate. It does not trigger eradication action or require any treatments on the part of property owners.

NDA also conducts trapping surveys for a number of other regulatory pests including Gypsy moth, emerald ash borer, Karnal bunt, Khapra beetle, and walnut twig beetle; soil surveys for potato cyst and Columbia root knot nematode; and this year will be doing surveys for a collection of exotic oak pests and several pests of small crops. 

Questions about regulatory plant pest programs in Nebraska can be directed to Julie Van Meter, NDA entomology program manager/state entomologist, at (402) 471-2351 or Julie.vanmeter@nebraska.gov