Posts Tagged ‘Cercospora’

Field Notes, June 28, 2010, Cercospora, chinch bugs

July 8, 2010

We used to call this disease Narrow Brown Leaf Spot, but because of its confusion with Brown Spot and the devastating impact it had several years ago we now refer to it as Cercospora.  Cercospora is the genus name of the fungus that causes the disease.  These symptoms tell us infection has already occurred, but is not the yield limiting phase of the disease.

This is  a close-up of some of the same leaves shown in the first photograph.  One major characteristic of this disease is the linear brown spots on the leaves.  They follow the veins of the leaves.  The phase that causes the most yield damage is the net blotch phase that shows up on the sheath of the flag leaf and on the stem.

Most of the time chinch bugs are a pest when they feed on young seedlings in rice fields that are not flooded.  Once the fields are flooded we usually forget about chinch bug injury to rice.  In this case seedling rice was being flooded late in the year and chinch bugs were reducing stand.  We expect the flood to take care of the problem.

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Rice Stink Bugs, Narrow Brown Leaf Spot, Cercospora, Panicle Blight

June 23, 2010

Yesterday we found lots of rice stink bugs in one of our verification fields.  Other folks out checking headed rice said they are finding them too.  If rice is headed they should be checked for stink bugs by sweeping with an insect sweep net.  We had more than one insect per sweep which is more than 3 times the threshold value.

We also found Narrow Brown Leaf Spot which is caused by Cercospora janseana.  At least two varieties were involed, CL161 and CL151.  Because of the confusion with Brown Spot the disease has been commonly called Cercospora to differentiate the two.  It requires propiconazole containing fungicides to control it.

In this heat we are also setting up for an outbreak of Bacterial Panicle Blight which will not be evident until grain development begins.