A fungal invader is making a serious dent in the quality of their blooms, but camellia fanciers are fighting back.

Around 40 per cent of entries at the national camellia show in New Plymouth on Saturday were showing signs of the brown spots caused by petal blight, a fungal disease.

This, along with the ravages of recent very wet weather and the ever advancing age of regular competitors, made it a fairly small show, New Zealand Camellia Society president and show organiser Tony Barnes said.

ANDY JACKSON/STUFF Competitors traveled from around New Zealand to attend the show.

"There are still some lovely blooms here."

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Rows of camellias ranging from tiny buttons of colour to blousy, saucer-sized numbers lined the tables in the Quality Hotel ballroom.

ANDY JACKSON/STUFF Cups of colourful camellias lined up on tables at the show.

Many of the flowers with brown spots had been clear of them when they were put out for judging, Barnes said.

"That's how fast it develops unfortunately. The spores would have been on the flowers and in the warmth overnight, boomph... it develops really fast."

However, behind the scenes, the camellia fanciers have gone into battle.

ANDY JACKSON/STUFF Lynette Hodge, Iona Ingram and Neil Ingram peruse the entries.

"The Camellia Society has spent a couple of hundred thousand dollars on research with Massey PhD students to try and find a cure," Barnes said.

Their allies in the quest have names like Sweet Jane, and Sugar and Spice.

"Some of these smaller species camellias are resistant to it, what we have to do is breed another round of new resistant varieties," he said.

ANDY JACKSON/STUFF Willow Henley, 11, admires some of the flowers on show.

"Then we will have to develop some new hybrids to increase the range of colour and flower size. It's a long term project."

Camellias, used extensively throughout New Zealand for hedging, are also getting help from a Russian PhD student, Nikolai Kondratev, who spoke about his research to members after the show.

"He's doing ground-breaking work on the interaction between the fungi and their host. He's working at molecular level on RNA and DNA to isolate what gene is responsible for resisting the blight," Barnes said.

ANDY JACKSON/STUFF The National Camellia Show is held in a different centre each year.

In most varieties, the blight produced an enzyme that 'tricked' the plant into killing cells in its healthy flowers in self defence, which caused the brown patches and provided nourishment for the disease, which feeds on dead plant tissue.

"It's certainly showing promise in our understanding of how the fungus attacks the plant and why some species resist it," he said.

But the winner of the FH Bethwaite Memorial Trophy for the show's champion bloom, Derek Beard from Tauranga, said he liked the flowers, which bloom in the coldest time of year, despite their blemishes.

ANDY JACKSON/STUFF Jenny and Derek Beard from Tauranga with their example of a camellia called Jamie that won them the champion bloom trophy.

He also enjoyed sharing them with native birds.

"Very few things flower in winter, and it's a bit of a highlight to see a couple of tui in the trees having a good feed on the pollen. That's part of the reason we grow the flowers. And for the waxeyes."