Can Polyphagous Invasive Tephritid Pest Populations Escape Detection for Years Under Favorable Climatic and Host Conditions?

Amid rising global travel and trade, early detection of tephritid fruit fl y pests is critical to preventing their establishment in many food-growing regions of the world (Suckling et al. 2016). Many countries operate extensive and continuous trapping programs to detect fruit fl y invaders and then be able to eliminate them, thereby protecting valuable fruit and vegetable industries. For example, trapping programs in the U.S. in California maintain more than 94,000 traps for non-native fruit fl y species (IPRFFSP 2006). Th ese traps are relocated every four to six weeks to diff erent properties during the year to follow the fruiting season, resulting in more than 300,000 properties being sampled annually (see Gilbert et al. 2013 for protocols). Th ese protocols are internationally accepted and comply with international phytosanitary standards (ISPM 26 2015). All areas in the state with suitable habitat for a population to exist year-round are trapped, with site densities ranging from 10 sites/mile (1 site/26 ha) to 1 site/6 mile (1 site/1554 ha) depending on environmental suitability, and trapping duration in a given square mile ranging from one month per year to year-round. Trap densities and durations are biased towards those areas where human-mediated introductions are more likely to be encountered, with the primary factors being international entry points, human population density, and environmental suitability. As a result, the highest trap densities and durations are in areas which have international access points (i.e., airports and seaports), high human population density, abundance of varied host plants providing year-round host availability for the fl ies, and an optimal climate for year-round reproduction. Other intensive surveillance programs currently operate around the world, such as in Australia (Jessup et al. 2007), Chile (Gonzalez and Troncoso 2007), Mexico, and Guatemala (Enkerlin et al. 2015). GERDA, the Global Eradication and Response Database (b3.net.nz/gerda), includes close to a thousand arthropod and plant pathogen eradication eff orts. An analysis of the subset that covered 211 eradication or emergency response programs against 17 species of fruit fl ies in 31 countries indicated that the failure rate for these fruit fl y eradication programs was about 7% (Suckling et al. 2016). Eradication success was generally based on the combination of several IPM tools and tactics applied on an area-wide basis. The likelihood of eradication Issues in Entomology: Tephritid Pest Populations