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There are enough things going on in our field that we wanted a plant
pathologist to inspect our field. This is Dr. Doug Jardine, extension
plant pathologist, and he's going to see if we've missed anything.
Right now, he's checking out some Rhizopus head rot. So, I guess he's
about to give us a lecture about Rhizopus.
Well, Doug found something that I had missed. These leaf spots are caused by the organism, Alternaria. If severe enough, Alternaria can cause premature defoliation and plant death and if it's on stems it can cause them to lodge or break over.
Well, this is interesting. There's an insect, called the sunflower head clipping weevil, which punctures the stem just below the head causing it to break off. But that's not what caused this damage. No, this damage was caused by the human head clipper! It appears that someone cut about a dozen heads near the edge of the field.
This is a critter that we don't like to see in a sunflower field. This
larva is a sunflower stem weevil. The larvae
This is typical bird damage. Birds land on the backside of the head and
then lean over the edge to pick out the