What's eating my sunflower stems?

My sunflowers were doing very nicely until a few days ago when I noticed that one had completely flopped, On examination I found that something had eaten all the way around the base of the stem to a height of about an inch. Another plant is starting to show the same signs.
Any ideas? Slugs? Mice or what?
Very annoying because apart from bring a nice splash of colour to one end of the veg plot, I save the seeds for the birds in winter



The base of the stem>

 

That's a weird one Dave. I don't know the culprit - but doesn't look like either slug or mouse damage to me. It looks more like some kind of grub or worm pest - or maybe some kind of viral/fungal/bacterial kind of blighter (that just about covers it :D) - I think that sunflowers are usually stronger than to wilt so badly with the little nibblish marks - its the brown oozing bruising that looks iffy. I've had sunflower stems cut in two, and sellotaped back together successfully, so reckon it must be something more.

Hope someone can help you out with a 'decent' answer soon - I feel for you - that is quite a loss!

 

Thanks JarBax - It's really strange that the damage has occurred when the plants are more or less fully established with pretty tough stems. I'm going to earth up the damaged stem on another plant tomorrow to see if that will help it survive.

 

Yeah - lots and lots of water too!

Fingers crossed!

 

Im sat here with nothing else better to do at this time and decided to search the www for this problem.
Came up with the following.

5. Stem and root-rot

Sudden wilting is seen when the plant gets infected near soil surface, it starts rotting up and down. The rotted portion turns black and a charcoal appearance is exhibited. The plant later droops down from the point of infection and dies prematurely. Seed treatment before sowing with 0.3% Thiram is recommended .

This is the link to the site
http://www.ap.nic.in/oilseeds/sepests.html.
Thanks for posting, I shall now be keeping a watchful eye on my sunflowers.
Capney

 

Hmmmm. My best guess would be that snails caused those nibble marks when the plant was younger and they let in some slow-acting rot or infection.

But I'm surprised that more of the stem hadn't gone manky before the plant collapsed. It might be worth carrying out a post mortem and looking inside the stem for more signs of damage or rot.

 

Thanks Capney & Flinty!
I've my doubts about stem and root rot Capney as there is no sign of 'blackening or charcoal appearance'
Flinty I'll cut a slice from the one that's collapsed most recently and post a photo in due course. My best guess at present is that it's due to something nibbling away the outer layer of stem.

 

Dave

Come to think of it, if "something" nibbled all the way round the stem, it might have the same effect as girdling, which is used to kill trees without/before felling them.

 

Cutworm


Cutworms are the caterpillars of various noctuid moths. They feed at night on the stems of young plants at ground level. Lettuce and brassica plants are particularly susceptible, along with carrots, celery, beetroot, strawberries and potatoes. Many ornamental plants suffer too, and damage can occur at almost any time of year. Plants grown both in the greenhouse and outdoors may be attacked. The worst attacks are often during dry summers, on light soil.