Sun flower problems
I am having a problem with my sun flower garden. I planted them four weeks ago, they emerge very well but for they are falling down and when up root i found the rot system ok. I found that the stem is drying immediately on the surface of the soil and fall down.(where the the stem touch on soil). No insect were found it is probably a desease but i do noy know, can help me? Thank you.
Outside United States
This does not look like insect damage, but more likely some kind of bacterial or fungal rot. If you do an online search for bacterial stalk rot in sunflowers you'll find lots of information. I've included one authoritative link that might help you identify the specific problem. There may be cultivation conditions in your area this season that favour the infection, but it is important to rotate your crops, as these infections can sometimes be soil borne and persist for several years.