white residue around plant roots

Katfish

Hi all
There is a raised bed in my garden that was put in by the previous owners.  I've noticed that plants tend to last only 1-2 years and then die off.  I thought perhaps it was because it was too shady for some of them, and then I thought perhaps the soil was depleted of nutrients.  So I've tried to address both of those issues and still I am losing plants after 1-2 years.
One thing I have noticed is that when I dig up a plant that is dying off it seems to have white residue around the roots.  I tried to take a photo but it doesn't really show it well.  It is as if someone has splashed some thin paint onto the soil around the roots.  There is nothing on the top of the soil to see, it is only around the roots of the plant.  It has happened with several different plants.
Can anyone shed any light as to what this could be?
Thanks

Loxley

Pretty sure it's the mycelium of fungi. It could be causing the problem, or it could be appearing after the plants start dying due to stress such as drought. 

//Symptoms

Saprophytic fungi are usually spotted in the garden in a couple of ways:

• White fungal growth (mycelium) in the soil, bark mulches or in compost
• Mushrooms or toadstools (fungal fruiting bodies) in lawns, on the soil surface, on woody mulches or on woody plants

Thankfully, the often extensive growth of mycelium in the soil or in compost is usually harmless. However, it sometimes has water-repellent properties, preventing water from reaching the roots of plants. In turf this type of growth is one of the causes of a problem known as ‘dry patch’.//

https://www.rhs.org.uk/advice/profile?pid=736

Katfish

Thank you. That does indeed look like a possibility.  

Now you've said it I would describe it as the fungus that you see on bark mulches.  Now I just need to work out whether it is the fungal growth that has some water-repellent properties and is causing the roots to dry out or if it was trying to help the roots of those plants because they were not getting enough water.

There are two raised beds and only one has this issue.  On that basis I'd like to think that the success of the other bed suggests that I wasn't blatantly neglecting them with lack of water.  So I wonder if it is an issue with improving the soil further so that it is more water retentive.

I had hesitated putting compost/fresh soil on the bed this year until I worked out what this was.  I didn't want to waste a load of lovely fresh compost and then find I had to dispose of it all because of a potential problem in the soil.  I think I'll get a load of compost onto that bed and hopefully give this year's plants a fighting chance.