Collaboration key to managing plant threats

Government, inspectors, public and nursery trade need to work together.

Xylella: outbreak would cause big problem for growers
Xylella: outbreak would cause big problem for growers

The future of managing pests and diseases lies in a collaborative effort between the Government and its inspectors, the public and the nursery trade. New assurance schemes that could isolate online rogue traders may be the way forward, industry figures suggest, after five years of relentless scares starting with ash dieback through red palm weevil late in 2016 and the ultimate perhaps likely to be Xylella, which is yet to hit the UK. Growers fear a 10km exclusion zone that an outbreak will bring.

Two of the most important figures in the sector spoke at the recent HTA/British Protected Ornamentals Association conference on the latest efforts to tackle the burgeoning number of pests and diseases coming into the UK on plants. Chief plant health officer Nicola Spence said the Government is spending £37m on tree health research from 2012 to 2019. Some 20 new plant health inspectors may be set to work, tackling unregistered importers, linked to the incoming EU plant and tree notification scheme.

Spence says the UK Plant Health Risk Register, developed in response to ash dieback three years ago, has added 100 new risks in the past year. Insects are the biggest issue, with 527 on the register. The future is still the implementation of the EU plant health regime, which Spence says will be reviewed after the UK leaves the EU.

Animal & Plant Health Agency principal inspector Ed Birchall says raising awareness, using plant passports and inspectors' surveillance and inspections are ways to prevent spread. But ultimately it is up to the nursery trade when Xylella comes. Spence notes all the other ways pests and diseases come in, particularly on wooden packaging for landscape stone, for instance. But ash dieback entered on imported trees and palm weevil came to Essex on imported palms.

On Xylella, he describes pre-border, border and internal strategies for stopping the disease reaching the UK from Europe. But he says Italy is now just containing the disease, which is "like a really bad cold" for plants, causing leaf loss and wilt on 360 host plants worldwide.

France, Corsica, Germany and Spain have also had outbreaks. The bacterium is spread by meadow spittlebugs, which are common in the UK. With the disease out in the wild on the continent, no one can give reassuring words on the UK avoiding it. But threats such as Xylella can mean the industry is more skilled at dealing with problems when they arise.

Birchall says growers should deal with other pests and disease threats by using the general concepts to prevent spread of Xylella, which has three subspecies. Interceptions can be dealt with easier than outbreaks, which mean 100m of plants destroyed around hosts and 10km movement bans, so it is worth reporting issues quickly before they spread.

Good practice includes using plant passports correctly, sourcing from known suppliers and disease-free areas, isolating, quarantining and monitoring new plants, keeping records, destroying unusable plants and being aware of the EU plant and tree notification scheme.

Speaking at a European Nurserystock Association (ENA) meeting at IPM Essen, nursery consultant David Brown said: "Forty ENA representatives decided what we really need is a subcommittee to work through things like 'is it possible to do a zonal approach to Xylella?'" Delegates remain worried about outbreaks, he added, but stringent EC rulings on five-year movement can be fine-tuned if ideas such as whether Xylella is temperature-dependent are scientifically proved. The ENA next meets in June when the subcommittee, including Brown, will present progress.

Threats - Pests and diseases

Sweet chestnuts are under threat from blight and gall wasp, with ash and oak also "under pressure". Sirococcus tsugae is another new issue for cedar and hemlock. On the horizon are Myzus mumeola on prunus in Italy, another "high-risk genus"; Illinoia liriodendra on tulip trees in the Czech republic; emerald ash borer in three new US states; and Asian longhorn beetle in the USA.

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