Detection Tools for a New Exotic Pest of trees:
Citrus Longhorned Beetle (Anoplophora chinensis)

Research Issue

[photo:] Male citrus longhorned beetle.  Notice the bumpy upper part of the wing coverings that distinguishes it from Asian longhorned beetle.The citrus longhorned beetle (CLB, Anoplophora chinensis) is a polyphagous (feeds on a variety of tree species ) wood-boring beetle native to East Asia. The insect has been intercepted in the United States before, including in a nursery in Washington where adults emerged from bonsai trees shipped to the nursery. Fortunately, the emerging beetles were observed, and a rapid eradication program was developed for the surrounding landscape. So far, an established infestation has not been found at that location. This event demonstrates both the potential for the species to be introduced again, and the advantages that comes with rapid detection focused on populations before they can expand. Citrus longhorned beetle has established in at least three countries in Europe, and the United States continues to be at high-risk for establishment. It is reported to develop on 108 tree species from 73 genera, but has a preference for Citrus, Malus, Acer, and Populus spp. Within its native range, CLB is the most important wood-infesting pest of citrus and a serious pest on other fruit trees. In Japan, 66 percent of their citrus trees have exit holes of this beetle, despite control programs being in place. Damage caused by CLB reduces yield and eventually kills the trees.

Currently, the only way to detect CLB is through visual surveys, and eradication depends on destroying infested trees by chipping. About 90 percent of the larvae develop below ground level, so tree stumps and roots must also be destroyed. Signs of CLB are difficult to spot; they can disperse up to 2 miles in a year so infestations of CLB can go unnoticed for several years.

There is currently no phenology model to predict when to monitor for CLB, or to identify what regions of the United States can support CLB populations. Station scientists have a phenology model for the Asian longhorned beetle (ALB), which is a close relative of CLB, that can be adapted for CLB once adequate information on its development has been collected.

In addition to knowing when and where to monitor, survey tools are needed for the citrus industry to detect infestations. Recently it was reported that CLB uses one of the same male-produced aggregation-sex pheromone components used by ALB. In ALB trapping experiments in China, collaborators of scientists with the Northern Research Station also caught CLB in traps baited with an ALB lure they had developed. However, more work is needed on CLB to optimize and adapt these lures and understand how to increase their detection ability by making raps more specific for CLB.

Our Research

[photo:] Citrus longhorned beetle (CLB) eggs laid at the base of a bolt of red maple supplies to a female CLB1) Determine CLB stage-specific temperature responses and produce a CLB phenology model.

We are rearing CLB mating pairs at temperatures between 10 and 35 degrees Celsius to assess the effect of temperature on adult survival, oviposition, fecundity and egg hatch. Larvae are being reared on an artificial diet at temperatures between 5 and 40 degrees Celsius to determine effects on larval development. These data will be used to estimate the lower and upper thresholds and degree days for each instar/stage over the temperature range to recalibrate the ALB model for CLB. These studies will be done using methods similar to those Forest Service scientists have used in studying ALB.

[photo:] Newly molted citrus longhorned beetle larvae with shed skin and head capsule near by.  Reared in artificial diet that mimics wood.2) Use CLB phenology model to predict geographic distribution of CLB and timing of adult flight for trap deployment.

The variable-instar, climate-driven, individual beetle-based phenology model for CLB will predict emergence of adults to guide timing of trap deployment, presence of different life stages throughout the year, and voltinism (years to complete a generation). This model will be used to identify geographic locations that are suitable for the beetle and regions where generation times may be short, indicating high risk for rapid population growth. This can be combined with other data sets like available hosts or transportation corridors to predict where CLB can establish. This objective can be accomplished quickly after the model is complete and tailored to the needs of the end users.

Expected Outcomes

  • Compiled, stand-alone phenology model for CLB to predict when adults will be present for timing trap deployment
  • Map showing areas in North America at risk for CLB establishment and development

Research Participants

Principal Investigators

  • Melody A. Keena , Research Entomologist, USDA Forest Service Northern Research Station
  • R. Talbot Trotter, Research Ecologist, USDA Forest Service Northern Research Station
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