Monthly Archives: August 2018

Silverleaf Whitefly in Cotton Update

WhiteflyBlogPic

Photo courtesy of: Joseph LaForest, University of Georgia, Bugwood.org

Here’s some information from Dr. Phillip Roberts, UGA Extension Cotton Entomologist:

Silverleaf whitefly (SLWF) adults have been observed in low numbers in cotton.  To date very few immature whiteflies have been observed in cotton.  We are not aware of any field which has exceeded threshold for SLWF.  Most reports include observations of individuals or a few adults when searching plants for corn earworm.  However, the presence of SLWF in a field is worth noting and management of all insect pests must consider the presence of SLWF.  All efforts should be made to minimize the need to treat SLWF with insecticide.

Management Considerations:

  • Scout for the presence of SLWF adults.  It is important to know if SLWF is present!
  • Conserve beneficial insects, do not apply insecticides for any pests unless thresholds are exceeded (beneficial insects will also suppress corn earworm).
  • If SLWF is present in a field, avoid use of insecticides for other pests which are prone to flare SLWF.
  • Scout fields frequently for adults and immatures once fields are infested with SLWF.
  • Be timely with SLWF insecticides when thresholds are exceeded (many learned in 2017 that it is difficult to play catchup with SLWF).
  • Be very aware of SLWF infestations in hairy leaf varieties and late planted cotton, these are high risk fields.

There is no question that agents, scouts, consultants, and growers are looking more closely for SLWF this year based on the problems we had in 2017.  Historically if we see SLWF in cotton during the month of July we should anticipate problems with SLWF, especially on late planted fields, and manage appropriately.  Infestations do not come close to where we were a year ago.  In 2017 treatable populations first occurred during the last week of June and many acres were treated in July; so we are in a much better situation this year compared to last.  It will be important that all fields are monitored closely for SLWF and hopefully proper proactive management can minimize damage and the need for SLWF insecticides.

 

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Target Spot

TargetSpot

Photo credit:  Jason Brock, University of Georgia, Bugwood.org

Target spot has been observed throughout South Georgia and is known to cause the most issues in fields with rank growth.  Growers with a crop between the first week of bloom and the sixth week of bloom may consider protecting their crop with a fungicide.  However, not every grower will benefit from this application and should scout fields prior to making this management decision.  This disease is characterized by leaf spots with concentric rings (shown above).  Defoliation begins at the lower leaves and progresses up the stalk.  Conditions are favorable for the disease and early detection is critical.  Once defoliation has reached more that 25% a fungicide application may no longer be feasible.

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