Raspberry Root Rot
I have planted several different varieties of raspberries in my plot over the last 4-5 years. All seem to thrive in the beginning only to wither and die in the second year. Curious as to why this was I started to look into the possible causes. Raspberries should grow in abundance in our wet weather. They are expensive to buy in the shops and shop bought berries don't keep that well. All the more reason to "Grow your Own"
The disease they suffer from is Phytopthora root rot and it does what the title says. You plant new stock, it thrives and then the second year it starts to grow. Gradually the leaves turn a brown crispy colour around the edges. If the plant goes on to produce fruit they are extremely small.Gradually the plant dies. This is root rot. The only thing that can be done is to dig up the infected plants and dispose of them in your normal bin or burn them.If you have root rot when you dig up the plant there will be very little left at the root. Normally just a stump with no healthy hairy white roots at all, the root stump that is left will be a reddish brown colour
This disease is dormant in soil. Once the conditions exist for the disease to attack the raspberries there is nothing that we can do. It is triggered by wet conditions. The fact that our plots are so wet over the winter creates the ideal conditions for the disease to spread. It seems particularly bad this year with plots that have had previously healthy raspberries badly affected. The disease may not kill all of the plants and there may be some that survive. These will normally be on the edges of the plot as they are less likely to have been sat in water for so long.
There is no chemical control for the amatuer grower. Various websites that I have visited advocate feeding the plants a high nitrogen feed to try and reinvigorate the plant. I couldn't find any feedback that this had worked.
All is not completely lost as there are several things that can be done if you want to try to grow raspberries. None are guaranteed but probably worth a try.
1.Buy stock that states that it is root rot resistant. There is one called Sanibelle and Marshalls say that Cascade Autumn Delight and Autumn treasure have resistance.
2.Plant the raspberries in a raised bed ideally in a hump with their feet way out of our wet clay. Incorporate plenty or organic matter to make the compost they are planted in free draining. I am going to plant with a depth of 10 inches. Another plot holder has a bed 18 inches high and so far so good.
3.Don't drown the plants when watering them.Little and often is best..
Non of these varieties or methods are guaranteed but by applying all three you are giving them the best chance. And lastly buy stock from a certified grower
The Scottish Crop Research Institute along with many other universities around the world are looking to breed new strains that will resist this disease. If you would like more detailed information there is a summary on the Scottish Crop research Institute's website. Just type Raspberry Root Rot into a search engine and it will come up. Also have a look at the Scottish Crop Research institute website. There are pictures which show the raspberries growing in humps. Recently when we had a lot of rain the area that was lower in between my raspberry rows was puddled with water so I think the humps work.
Let us know how you get on. I'll post updates as soon as I have them.
Update 24 May 2013. Planted Sanibelle,Autumn Treasure and Cascade Delight. So far they are all lovely and green with plenty of buds showing.More to follow later in the season.........................
So far the Sanibelle have done well. The Autumn Treasure was good as well. Cascade Delight I had replaced twice and I will see how these do this year.
Glen Ericht was another new variety that was on the Beechgrove Garden this year. It has good root rot resistance. Not so good for fresh use but good for freezing and processing so I assume good for Jam. It is available from R W Walpole LTD. Discounts for bulk buying so may be worth getting together. Not available in the garden centres yet
Sanibelle is available from Lubera
Autumn Treasure and Cascade Delight just tap into a search engine and the suppliers will come up
UPDATE AUTUMN 2015
Sanibelle - still doing well
Autumn Treasure - Gradually dying back from the top of the row to the
bottom. Will wait to see what happens next season
Cascade Delight - This one has really good flavour. Also dying back
Glen Ericht - I have been told that this variety has not got much flavour
I am not sure if the die back which started earlier this season is a result of some of the plants being sprayed with the red diesel that was used during the vandalism last year. It could be the patchy weather we have experienced this year. It has not been very consistent.
I intend to cut them back by half, give them a high potash feed and mulch with compost from Polmaise. Give them a high potash feed again at the beginning of next season and see what happens.
I will post the results.
The Autumn Treasure and Cascade Delight mostly died back. Some of the Cascade Delight survived with no real obvious reason. Some of these plants were in the middle of rows. Sanibelle still growing strong,
Sanibelle still going well so would seem to be the most resistant to root rot. Cascade Delight and Autumn Treasure do well in some plots. Autumn Bliss is also well established in some plots. To be sure of a crop plant at the highest point in your plot and use Sanibelle.
Sanibelle is a strong grower and is resistant to root rot. It out performs the other three varieties mentioned and is consistently reliable. The other three on our site can have variable results. Although established plants do well. Planting In a raised position keeps roots out of water. Also planting in the highest position in your plot will yield better results. Feeding with potash should make the fruit sweeter.