A Tasmanian garlic grower could face jail time after she illegally imported more than 2,000 garlic bulbils from Canada and the United States that could have contained a devastating plant disease.

Key points: Letitia Ware illegally imported more than 2,000 bulbs from the US and Canada

Letitia Ware illegally imported more than 2,000 bulbs from the US and Canada Ware instructed suppliers to mark the bulbs "office supplies" to avoid detection

Ware instructed suppliers to mark the bulbs "office supplies" to avoid detection The varieties imported by Ware are known to host a plant pathogen which could devastate the agriculture sector

Letitia Anne Ware, 53, pleaded guilty to three counts of aggravated illegal importation of plant material and seven counts of importing conditional non-prohibited goods.

The court has been told the varieties of garlic Ware imported were known hosts of xylella fastidiosa.

The bacterium is listed on the Australian Government's Department of Agriculture website as the country's number one plant pest threat.

It has devastated more than 60 per cent of Brazil's citrus industry, cost the Californian economy more than $1 million a year and has been blamed for an olive oil price rise across the European Union.

The court heard Ware used several eBay accounts to import Romanian, French and Korean varieties of garlic from Canada and the United States over an 18-month period.

Commonwealth prosecutor Thomas Jones said Ware had instructed suppliers to mis-declare the contents of packages as "office supplies" and break up items to under 150 grams each to avoid quarantine detection.

When police and taxation officers executed a search warrant on Ware's 40-acre property they seized 18 international packages, one containing 400 garlic bulbils.

A cross-contaminated area of her farm where illegal garlic had been planted was destroyed, the court heard.

Imports put agriculture sector 'at great risk'

Garlic products are required to have an importation permit, a certificate declaring them free of any pests and diseases and must be subject to rigorous fumigation treatments on arrival.

Mr Jones told Justice Gregory Geason Ware's offending was "arrogant and repeated", deliberately dishonest and was motivated by gaining a commercial advantage.

The pathogen is listed as the biggest threat to the country's agriculture sector. ( Supplied: Department of Agriculture )

He said her offending posed a serious risk of devastating Tasmania's Agricultural sector and he asked for a "stern penalty".

"Xylella fastidiosa is the last thing anyone wants coming in to the country," he said.

"The potential damage from infestation would be devastating."

Defence barrister Ian Arendt told the court Ware, who is also the chairwoman of the Australian Garlic Industry Association, was at risk of losing her business and home as her farm had not been profitable for several years.

He described Ware as a single woman with no children and a passion for garlic and urged Justice Geason to impose a wholly suspended sentence.

"She's the lead person in the garlic society and yet she's quite prepared to import not once, not twice, garlic that could be diseased at great risk to Tasmania's agricultural industry and the nation's," Justice Geason said.

"The fact that they weren't diseased is just good luck.

"This conduct is difficult to detect so a harsh penalty is needed to cause others to pause before engaging in similar activity."

Justice Geason has reserved his decision and Ware will be sentenced at a later date.