TECHNICAL | PPC102 MARCH 2021

In this article, Nikos T Papadopoulos from the Laboratory of Entomology and Agricultural Zoology at University of Thessaly, Greece, writes about the threat to fresh fruit and vegetable production from invasive species and how a new project aims to plug a research gap on fruit flies in Europe.

SPEED VIEW:

• Invasive species are given greater mobility by the expansion of global trading and travel
• The problem of invasive pests is complex and requires high levels of integration and various approaches to be tackled
• True fruit flies, species of the Dipteran family Tephritidae, is perhaps the most important group of pests for fresh fruits and vegetables worldwide
• The Horizon 2020 FF-IPM project will help determine the success of biological invasions in the context of climate change and help European countries tackle important new invaders.

Biological invasions, defined as the expansion of the geographic distribution of species into new areas that do not host established populations of this species, are a major threat to
biodiversity, ecosystem function, sustainable agricultural production, agricultural cropping patterns, pesticide use, both national and regional economies, and public health.

Increased goods trading at a global scale, as well as intensified human mobility that is reported over the last few decades, tremendously increased the arrival of harmful organisms into novel areas (see figure 1).

Climate change relaxes the barriers of surviving and reproducing into invaded areas, substantially contributing to the successful completion of the invasion process. Hence, new pests are emerging as major issues for crop production and trading of agricultural commodities all over the globe.

Direct effects of invasive pests include the loss of plants, yield reduction, increased pesticide use and major income losses.

Additionally, indirect effects on the trading of agricultural commodities may be even more dramatic, ranging from demands for disinfestation treatments by the importing partners that adds to production cost, to rejections of cargo shipments at arrival spots and the complete loss of markets.

The problem of invasive pests is multidimensional and complex, and requires high levels of integration and various approaches to be tackled.For example, new and thorough updates of existing legislation might be required to regulate trading.

Novel interception tools for both commercial shipments and goods carried through human travelling should be considered to prohibit arrival of invasive pests.

In addition, new, more effective, tools and strategies should be considered for early detection of established populations, and aggressive eradication and containment campaigns should be enforced to address the newly established populations.

True fruit flies, species of the Dipteran family Tephritidae, is perhaps the most important group of pests for fresh fruits and vegetables worldwide.

Out of more than 5,500 described species of the family, more than 250 non-resident ones are considered as possible quarantine pests for Europe according to a recent investigation of the European Food Safety Authority (EFSA 2020).

Females of these small creatures drill an invisible hole on the peel of the host fruit and oviposit usually a clutch of eggs in the flesh. Hatched maggots feed on the juicy part of the fruit by digging tunnels in the mesocarp (see figure 2).

Often bacteria and fungi invade the infested fruits further contributing to destroying the fruit. Because it is hard to notice at harvest or at the packing house, infested fruits can travel long distances with human assistance.

This cryptic life cycle, and the increased demand for exotic fresh fruits and vegetables worldwide, renders fruit flies on the top of the list of invasive agricultural pests. Indeed, fruit flies are the most commonly intercepted group of pests in European ports of entry.

Approximately 33% of all interceptions in fresh fruit and vegetables in Europe regard fruit flies (see table  below).

This high propagule pressure (frequency and number of individuals of a species that arrive in a new site) results in increasing detection of fruit flies in Europe. Indeed, over the last decade, two tropical fruit flies, the peach fruit fly (Bactrocera zonata) and the oriental fruit fly (Bactrocera zonata) have been detected in Austria, Italy and France.

Officially all these detections are considered transient resulting from non-established populations.

In addition, the Mediterranean fruit fly (Ceratitis capitata), an old resident of the warmer coastal Mediterranean orchards, is currently expanding its geographic distribution to northern, more continental fruit growing areas, posing an additional burden on the deciduous fruit industry of the central European countries.

Establishment of the above, and possibly other invasive fruit flies in Europe is expected to result in major economic losses for fruit growers and traders.

Financial impact of fruit flies

Estimates of economic losses in other than Europe geographic areas because of the activity of invasive fruit flies are quite dramatic.

For example, estimated annual losses because of the failure to eradicate the oriental fruit and the Mediterranean fruit fly in California range from US$176 million to US$1.8 billion (Papadopoulos et al 2014).

Likewise, the invasions of Bactrocera papaya into north Queensland caused losses of AUS$100 million (Clarke et al 2005), and its recent eradication cost AUS$34 million (De Meyer et al 2008).

...estimated annual losses because of the failure to eradicate the oriental fruit and the Mediterranean fruit fly in California range from US$176 million to US$1.8 billion.

The Horizon 2020 funded project FF-IPM - “In-silico boosted, pest prevention and off-season focused IPM against new and emerging fruit flies” aims to fill the current gap of coordinated research on aspects related with the invasive fruit flies in Europe.

The FF-IPM project refers to three fruit fly species that cause significant losses in the production and marketing of fresh fruit worldwide, the Mediterranean fly, which in recent years is threatening even temperate regions of Europe, as well as the Oriental and the peach fruit flies. In the last few decades, these have expanded their geographic distribution to areas neighbouring Europe and frequently arrive via infested fruits into Europe (see figure 3).

The broader aim of the project is to (a) prevent through the effective implementation of measures in the early stages of the insect invasion process and (b) tackle established species in out-of-season periods considered crucial for the development of their populations, introducing the off-season management as a new concept in IPM.

In this context, innovative tools will be developed to:

• Prevent the introduction of infested fruits
• Locate populations in the early stages of the invasion
• Establish biological control and response strategies based on the use of thorough ecological modelling, and appropriate hardware and software.

Pilot tests are to be carried out in eight different countries. The results of the project will help to understand the factors that determine the success of the installation of biological invasions in the context of climate change, and to prepare European countries to tackle important new species of invaders, by promoting the production and marketing of fresh fruits and vegetables.

By preventing invasions of new fruit flies species, shifting IPM approaches to new concepts such as that of the off-season management, and in-silico boosting of current IPM tools, the FF-IPM project is expected to contribute towards maintaining the productivity and sustainability of the fruit-producing industry in Europe.

During the course of the project novel new data will be generated regarding the drivers of plant pest invasions and possible effects of climate change.

The FF-IPM project is funded by the European Union under Horizon 2020 and coordinated by the Entomology and Agricultural Zoology Laboratory of the University of Thessaly. The project consortium consists of 21 partners from 15 countries (10 European, Israel, South Africa, China, Australia and the USA).

Find out more about the Horizon 2020 FF-IPM project at fruitflies-ipm.eu

References cited

Clarke, AR, Armstrong, KF, Carmichael, AE, Milne, JR, Raghu, S, Roderick, GK and Yeates, DK 2005. Invasive phytophagous pests arising through a recent tropical evolutionary radiation: The Bactrocera dorsalis complex of fruit flies. Annual Review of Entomology.
DeMeyer, M, Robertson, MP, Peterson, AT and Mansell, MW 2008. Ecological niches and potential geographical distributions of Mediterranean fruit fly (Ceratitis capitata) and Natal fruit fly (Ceratitis rosa). Journal of Biogeography, 35, 270-281.
Papadopoulos NT, Plant RE and Carey JR, 2013. From trickle to flood: the large-scale, cryptic invasion of California by tropical fruit flies. Proceedings of the Royal Society B no. 208: 30131466.

Source: PPC102