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Dr. Doug JardineThere 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. 

Rhizopus MyceliaInside this Rhizopus-damaged head you can see these thin mycelia strands and black, pinhead size fruiting
bodies called sporangia.

Early RhizopusThis 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.  

AlternariaWell, 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. 

Human stem clipperWell, 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. 

Stem weevil in stemThis 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!)

Stem weevil close upThis is a closeup of the sunflower stem weevil larva. They are C-shaped, creamy white and have a brown head

Seed from bird damageSeeds 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.

Bird damageThis 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.