Fusarium oxysporum and pests

[Croquin]

Dear Croconuts,

crocuses can be attacked by fungals like Fusarium oxysporum, Penicillium, Rhizoctonia, Sclerotium, etc.

when you start growing crocuses for good, or exchanging/buying corms, you increase the chances to see one of these problems occur and spread in your collection.

what is the experience of seniors with this matter, how do you deal with an infection and get rid of it ?


concerning pests, we had a situation with Arvicola last year - we call them campagnols in french, I'm not sure if it is what you call voles in English ?
they attack unnoticed, in the underground, harvesting corms according to an industrious scheme.
they peel them and use the peelings for their nests, it seems comfortable.
then, they build chambers where they store the corms (for winter I guess) - very few were eaten.

the problem is that they also reproduce fast and can damage a crop significantly before you know it.

what are your technical approaches to avoid facing these types of issues ?

[Lesley Cox]

Sclerotium species are totally destroyed by the fungus Trichoderma in horticultural/agricultural crops such as lettuces, tomatoes etc. Maybe the other fungi you mention are also. Trichoderma is available worldwide in a variety of brand names and different forms. Worth trying on your crocuses if there is a fungal problem.

[Janis Ruksans]

If corm/plant has infection the single real remedy is to destroy infected plant. Carefully check corms before planting. All suspicious destroy. Plant in sterile soil mix. Although modern fungicides are offered now not only for protection but for cure, too - really it didn't works. Keep all newcomers separately up to checking health (especially viruses - many commercial stocks now are infected) and only then add to main collection. Select good source for new plants.
Janis

[Croquin]

Leslie, this is very interesting. Thanks !
I am willing to privilege biodynamic balances and biological control such as the one you have mentioned.
I planted corms with mycorrhizal inoculates, which proved to be extremely good last year, and is said to have protective properties against fungal infections.

I currently run a little experiment in which I'm comparing phenotypes of Crocus sativus strains from different geographical origins.
On the one hand we have scientific works on the genetics of Crocus sativus stating that all strains are genetically identical (but published analyses were not run on the full genome).
On the other hand, saffron growers report significant differences in growth, plant aspect, crop, etc.
Since these differences can be of environmental origin, it needs to be tested in plant lots cultivated in standardized conditions.

Therefore, I had to get corms from various places.
Most of the lots were clean and plants have developed without trouble, but those coming from Spain really have a sanitary issue, and I can only warn croconuts about this.
I had to refuse a full lot infected with Fusarium oxysporum (some of the corms arrived half rotten and the producer refused to take them back and to reimburse).
My second lot from Spain seemed to be clean (all corms - from all lots - were checked for traces of infection under their tunics, and great care was taken in manipulating them for avoiding cross-contamination between lots).
This second Spanish lot is now showing symptoms in its vegetation, due to corm rot, probably by fusarium.
Fusarium is a major issue in Spain and Italy saffron fields.

I'm currently trying to stop the disease progression by taking the infected plants out of the ground, but I fear this will not be very efficient if the fungi has contaminated the soil.
Not being a farmer, I do not have access to phytosanitary molecules but those perfectly useless that are sold to the general public.

I'm really pissed at these Spanish producers and the sanitary services, which participate in propagating diseases in Europe (which is obviously good for some industries), but I do not know what to do for solving this issue before it reaches another level.

A saffron grower told me that fusarium was spreading mainly in acid soils, is this true?

[mark smyth]

Croquin, Arvicola in English are water voles

[Croquin]

thanks.
I used Arvicola as the latin name for a genus.
do you see which one I'm referring to (the ground one, not the water one)?
what is its english name ?

[mark smyth]

OK - bank vole or maybe field vole.

[Janis Ruksans]

Their are voles, but translating Latvian name - water-rats. Very carefull animal to poisons and traps. Extremely difficult to eliminate. In France are special trap with explosive blowing up when rat touch (information got from Antoine Hoog - it works with him). I replaced all my crocuses in containers, otherwise not worth to grow. Real nightmare here.
Janis

[Croquin]

they learn not to touch it after one or two members of the clan had the experience.
same with mechanical traps: only for cooperative or suicidal rats, the others will laugh at you.

use this (not for containers or greenhouses though):
http://www.rodenator.com/
much better

what about fusarium and fungi ?
any thoughts ?

[Lesley Cox]

Prevention is always better than cure of course and I now use a very small amount of Trichoderma granules in all my potting mixes, with great success. It has also stopped any appearance of the brown spots that appear during and after flowering on bearded irises. Used in its dowl form and pushed into same-sized holes in trees, it will cure totally, silverleaf disease in maples, apples, pears and other ornamentals. It takes about two years to be totally effective but that's better than pulling out what could be precious, productive or rare trees.

[Croquin]

Thanks Lesley, I have studied this track after you mentioned it, I did not know about it before and it looks very promising.
I will try it ASAP.

[Maggi Young]

For anyone new to the Forum who hasn't seen the thread on Trichoderma, as mentioned by Lesley
... it is here: http://www.srgc.org.uk/forum/index.php?topic=6697.0

[Croquin]

Thanks 

[Croquin]

Leslie,

I have a question for you as you are THE Trichoderma expert here.

I have studied further this topic and it seems that the fungi is biologically active (growing and biocontrolling) in warmth (25-30°C).

I find that it would be worth trying a cure on my C. sativus bed infected with Fusarium oxysporum, but now, the ground temperature at the corm level must be below 15°C, and my best guess is that it is probably closer to 10 than to 15°C.

Did you observe any cure or improvement with your treated plants when the weather was fresh, if this happens where you live ?
What do you know about this temperature thing ?

Thanks in advance.

[Lesley Cox]

I hope I haven't given you any false ideas about my "expertise" on this or any other subject. Of all the Forumists I am probably the least scientifically minded. Roger, my partner, says of just about every subject, "It's electrical. You wouldn't understand it" and many times he's be right so I haven't taken any7 notes regarding temperatures of active Trichoderma products. I use it when potting or sowing seed and this happens through the year except in, perhaps June and July wheich are the coldest months here and even then, I still sow seed if I have any to sow. I would use the trichoderma in warmer months for planting (2 large hybrid clematis were planted yesterday, each with granules dug into the soil around the planting holes).

I think it's right to say that the fungus is active in warmer temps but I'm not sure what the range would be. I work on the assumption - which may be quite incorrect - that if it's too cold when I use it, it will stay inactivate until the compost warms then activate when a high enough temperature has been reached. Having uded it in a number of different applications, I've never had the thought that it was wasted because I used it at the wrong time.

Living in the southern half of the South Island of New Zealand, I suspect our temperatures may be similar to those of Tasmania in Australia, or to the south of England but this may be wrong too. In Dunedin which is not exactly where I live but approximately similar, we have frequent summer temperatures in the daytime of around mid twenties and sometimes up to low thirties while winter temps are rarely lower than say -3 or -4C in the city, sometimes a little lower where I live.