What is wrong with my sunflowers??

[mercury]

I am trying to grow sunflowers either side of a north-south fence, and against a south facing wall. I put the seeds in on May 1, which was "International Sunflower Planting Day". The seeds worked (hurray!) and the seedlings are about 3 or 4 inches high.

The problem is they all have some leaves that are thin and eaten, some leaves that are crinkly and curled up, and some that are going yellow and drooping.

Example 1:



Example 2:



I don't understand what is the matter because I've no experience. I thought I'd put lots of water on them with a watering can, I don't have a hose pipe. What am I doing wrong?

[Treewheeler]

Have a look at the roots... (ie) Are there any...? could be insect damage underground.
Does a dog piss there? Could be piss burns...
 Although... it does look like phytophthora which is a kind of potato blight.
Better to bung some new seeds into pots using fresh clean sterile compost this time and get them going indoors to catch up.
 Better luck next time!

[Kathy]

Example 1:



Example 2:

From what I can see of those photos, there are necrotic (i.e. dead) spots on those leaves. The first photo looks like there are chlorotic spot too. Do the leaves display a mottled appearence with paler blotches on them before the patches of tissue die? If so, I'd reckon that you've got a virus problem, possibly with mildew developing on the dead bits.* It would have been transmitted by aphids and other piercing insects.

If it is a viral infection, there's not much you can do other than grub-and-burn. You might be able to heat-treat the plants (put them in a greenhouse and repeatedly blast them with periods of extreme heat, interspersed with "normal" temperatures. However, heat-treating doesn't always work, and often kills the plant too.

More info here:

List of sunflower diseases - Wikipedia, the free encyclopedia

*Caveat - I used to do plant viral research, specifically into mottle viruses, which is why I think that. However, as the old (niche) joke goes, if you put a fungal expert, a plant nutritionist, an entomologist and a virologist in a field and show them a plant, the fungalist with say it has a fungal infection, the nutritionist will claim it has a mineral deficiency, the entomologist will blame a parasitic insect, and the virologist will declare that it has a viral infection. And more often than not, the plant in question will be perfectly healthy anyway!