Root Rot

[Gerry Webster]

Can anyone suggest a fungicide currently available in the UK which might deal with this? A Pythium infection I presume. The most severely affected plants  seem to be bicolour forms of C. niveus.

[Janis Ruksans]

Can anyone suggest a fungicide currently available in the UK which might deal with this? A Pythium infection I presume. The most severely affected plants  seem to be bicolour forms of C. niveus.

Dutch growers use soil fungicides shortly before planting. Chemical treatment of harvested corms can help, too, but most of specific fungicides against Pythium are now forbidden in the EU. So, I think, at present there is no real remedy against it, only replanting in clean soil.
I don't know about availability in UK, but some years ago in Holland on open fields were used RIDOMIL - 15 kg per ha and for Crocus potting mix ALIETTE - 150 g / 1 c.m.
Pythium is one of the greatest problems. If chemicals are not more available (or not available in UK) I can reccomend only cleaning at harvesting with washing of corms from all soil remnants and replanting in fresh, new artificial mix, only one corm per pot and keeping for further growing only healthy specimens.
Janis

[Gerry Webster]

Thanks Janis. Unfortunately, neither of the fungicides you mention seems to be available in the UK. One that is available is called ‘Proplant’ (propamocarb hydrochloride) which is said to have a protective action (but little curative effect) on pythium, phytophthora & other fungi. It can be used with bulbs as a dip & a soil drench. I haven’t been able to find out whether it is available to amateurs.

I have seen it suggested that extra potassium can help with root rots. What do you think?

[Ian Y]

I have seen it suggested that extra potassium can help with root rots. What do you think?

As well as many other beneficial properties potassium, boosts the plants immune system which could help it resist such rot and fungal infections.

I am also a believer in making sure there are plenty of the trace elements available to give the plants every chance to keep healthy and ward off attack.

Also I have always been wary of using such fungicides as they are none selective and kill all fungi many of which are beneficial if not essential to the general health of the bulbs.
 
Fungi can be territorial so good fungi will ward off those which can harm the bulbs and if you kill them all with fungicides I suspect that the harmful ones re invade quicker than the beneficial.

For this reason, once you have gone down the fungicide path, it is difficult to stop.
Too much use of fungicides can lead to resistant strains and then you have a problem.

I am always much happier using the organic ways.

I have heard of people dipping the bulbs in a bleach solution at re potting time which may help.

[Oron Peri]

I have seen it suggested that extra potassium can help with root rots. What do you think?

As well as many other beneficial properties potassium, boosts the plants immune system which could help it resist such rot and fungal infections.

Ian,

Can i ask how often do you add potassium to your Crocus?

[Maggi Young]

Oron, we would not add potassium to the crocus flowering now.... we wait till the weather improves in early spring and then feed as the growth of the leaves begins after the winter slowdown. For the Spring flowerers, they get fed after the flowers are passing and , if the growing season proves to be a good long one, they may be fed a couple of times over the season.

[Gerry Webster]

Ian - thanks for your comments. I'll try the effect of potassium sulphate. Since the potting mix - which is well-drained -  contains Vitax Q4 I don't think there can be  a shortage of trace elements.  These forms of C. niveus (seed raised) seem particularly susceptible to root rot; they get it every year to some extent but this year it is particularly bad. Although I am inclined to agree with you about the use of fungicides I don't want to lose the plants so I'm prepared, for once, to contemplate drastic measures.

[Oron Peri]

Oron, we would not add potassium to the crocus flowering now.... we wait till the weather improves in early spring and then feed as the growth of the leaves begins after the winter slowdown. For the Spring flowerers, they get fed after the flowers are passing and , if the growing season proves to be a good long one, they may be fed a couple of times over the season.

Maggi
Thanks for this information.

[derekb]

Ian - thanks for your comments. I'll try the effect of potassium sulphate. Since the potting mix - which is well-drained -  contains Vitax Q4 I don't think there can be  a shortage of trace elements.  These forms of C. niveus (seed raised) seem particularly susceptible to root rot; they get it every year to some extent but this year it is particularly bad. Although I am inclined to agree with you about the use of fungicides I don't want to lose the plants so I'm prepared, for once, to contemplate drastic measures.

Gerry I use a fungicide called Subdue for root problems on my Disa but the trouble is you would have to know a Grower to get it mine came from FARGRO it is very dear nearly £100 for 250mltrs.

Derek

[Gerry Webster]

Thanks Derek. I got details of the fungicide I mentioned above ('Proplant') from the FARGRO website. Although they mainly sell to the horticultural industry, I know from experience that they will  sell some things  to amateurs (e.g., me) but I don't know how much this fungicide costs nor the quantities in which it is sold. I would guess expensive & large.