Pathways for accidental biocontrol: the human-mediated dispersal of insect predators and parasitoids

Authors: FENN-MOLTU, GYDA - Lausanne University Hospital; LIEBHOLD, ANDREW - Us Forest Service (FS); Weber, Donald; BERTELSMEIER, CLEO - Lausanne University Hospital

Submitted to: Ecological Applications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Unintentional introductions of insect natural enemies (predators and parasitoids) exceed species introduced intentionally. Accidental or unintentional biological control brings with it several disadvantages: candidates are not chose logically; generalists may be favored, increasing negative nontarget effects; genetics as well as pathogens and hyperparasitoids are not controlled. On the positive side, unintentional biological control is often rapid and is cost-free; it is occasionally superior to prior intentional introductions; there are even good examples of accidental introductions that would be judged successful if intentional. On balance though, compared to highly controlled intentional introductions for biological control, the unintentional transport of diverse natural enemy insects has potential for considerable ecological impacts, both in terms of controlling pest species through accidental biocontrol and by disrupting native communities. An important aspect of biosecurity is learning from interception data what imported materials are most likely to harbor propagules of non-native species. This study analyzes interception data for the US provided by USDA APHIS, specifically, predatory and parasitic insect interceptions. The data is highly infomative as to taxonomic distribution, classes of goods that harbor potential natural enemy introductions, and regional origins of these interceptions. There were 35,312 interceptions of insect predators and parasitoids during this period, representing 93 families from 11 orders, and 196 species from these families. While commodity associations were variable, imported plants and plant products were the main introduction pathway. Characterizing the insects being transported and their introduction pathways can inform biosecurity practices and management. This study is of interest to those involved with prevention and mitigation of invasive species impacts.

Technical Abstract: The introduction of insect predators and parasitoids for biological control is a key method for pest management. Yet in recent decades biological control introductions have become more strictly regulated and less frequent. Conversely, the rate of unintentional insect introductions through human activities is rising. While accidental introductions of insect natural enemies can potentially have serious ecological consequences, they are challenging to quantify as their movements go largely unobserved. We used border interception records collected by the US Department of Agriculture from 1913 to 2018 to describe the diversity of insect predators and parasitoids transported unintentionally, their main introduction pathways, and trends in host specificity. There were 35,312 interceptions of insect predators and parasitoids during this period, representing 93 families from 11 orders, and 196 species from these families. While commodity associations were variable, imported plants and plant products were the main introduction pathway. Most interceptions originated with commodities imported from the Neotropical, Panamaian and Western Palearctic regions. Among the intercepted species, 27 % were found in material originating from more than one country. Two thirds of species were polyphagous host generalists. Furthermore, 25 % of species had already been introduced intentionally as biological control agents internationally, and 4.6 % have documented negative impacts on native biodiversity or human society. Most of the intercepted species that have not yet established in the USA are host generalists or have at least one known host species available. The unintentional transport of diverse natural enemy insects has potential for considerable ecological impacts, both in terms of controlling pest species through ‘accidental biocontrol’ and disrupting native communities. Characterizing the insects being transported and their introduction pathways can inform biosecurity practices and management.