Scientists discover new species of a root rotting disease that is killing popular holiday trees 

A newly discovered water mold could ruin Christmases yet to come.

Scientists have found that Fraser firs are highly susceptible to devastating root rot diseases that are killing the trees within just three years of being planted.

Testing has confirmed that the mold is a new species of Phytophthora, or water mold, which could threaten the tree for future holiday seasons.

Fraser firs are highly prized for the holidays because of their rich color and pleasant scent, as well as their ability to hold their needles.

However, scientists in Connecticut were conducting experiments testing various methods to grow healthier Fraser trees when they accidentally discovered a new species of Phytophthora.

The team noted in the study that 900 hundred Christmas trees were planted in Brooklyn, Connecticut in 2010, 60 of them were Fraser fir.

With just three years, all the Fraser in this field had died – leading experts to investigate the cause behind these deaths.

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Scientists have found that Fraser firs are highly susceptible to devastating root rot diseases that are killing the trees within just three years of being planted. Testing has confirmed that the mold is a new species of Phytophthora, or water mold, which could threaten the tree for future holiday seasons. Pictured on the left is an infected tree, while the right is a healthy one

‘In a new experiment, five-year-old bare-root Fraser fir seedlings were replanted in 2015 in this field, reads the study published in the journal Plant Disease.

Ten of them were investigated by the researchers and ones that showed signs of poor color or chlorotic foliage were transported to the lab for further testing, which is when the team found the new form of water mold.

Also of note, this research was conducted using apples to do the initial isolation of Phytophthora, a method that dates back to 1931, demonstrating that old methods in plant pathology are still valid and useful.

They collected the diseased plants, isolated and grew the pathogen on artificial media, then inoculated it into healthy plants before re-isolating it to prove its pathogenicity.

They collected the diseased plants, isolated and grew the pathogen on artificial media, then inoculated it into healthy plants before re-isolating it to prove its pathogenicity. Pictured in A is the new species, the rest are existing molds found in trees

Also of note, this research was conducted using apples to do the initial isolation of Phytophthora, a method that dates back to 1931, demonstrating that old methods in plant pathology are still valid and useful

Rich Cowles, a scientist at the Connecticut Agricultural Experiment Station involved with this study, said: ‘Once the organism was isolated, the presence of unusually thick spore walls alerted us that this may not be a commonly encountered species.’

‘So comparison of several genes’ sequences with known Phytophthora species was used to discover how our unknown was related to other, previously described species.’ In fact, they had discovered a new species altogether.’

The fact that these scientists so readily discovered a new species of Phytophthora infecting Christmas trees suggests that there could be many more species waiting to be discovered.

Recognizing the greater biodiversity among this genus infecting Christmas trees is important.

Fraser firs are highly prized for the holidays because of their rich color and pleasant scent, as well as their ability to hold their needles

Transportation of infected nursery stock and chance encounters of different Phytophthora species in the field can lead to new hybrids arising, which can have different pathogenic characteristics than their parent species.

‘Knowing how many and which species are present is important, not only for Christmas tree growers, but also for protecting our natural environment,’ Cowles adds. 

‘Combining this robust old technique worked well with modern molecular biology methods to isolate, and then identify our unknown plant disease.’