 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.
 Inside this Rhizopus-damaged head you can see these thin mycelia strands
and black, pinhead size fruiting
bodies called sporangia.
 This is a different head that's just starting to show symptoms of
Rhizopus head rot. You can see the tissue
darkening in the center of
the receptacle.
 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
tunnel in the stem or stalk and
weaken it, which eventually causes the stalk to lodge or break over.
When a plant lodges then it can't be harvested and that results in yield
losses. (Nice New Balance shoes, Doug!)
 This is a closeup of the sunflower stem weevil larva. They are C-shaped,
creamy white and have a brown head
capsule.
 Seeds on the ground! That isn't a good sign. What's your first
guess? If you said bird damage, you guessed right. You might see seeds
on the ground after a hail storm, too.
 This is typical bird damage. Birds land on the backside of the head and
then lean over the edge to pick out the
seeds. Sometimes they drop them on
the ground as we saw from the last picture. House sparrows are
especially bad about causing damage, as are blackbirds. I've noticed
several mourning doves eating seeds on the ground. Notice how wilted
the leaves are. It is really dry.
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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.
