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Wednesday, July 31, 2013

Lygus Reach ET in a Few Fields

Lygus have been a common occurrence in our cotton fields so far this season, but we had not seen any fields at economic threshold (ET) until today.  This morning we double checked a couple of fields in Swisher County behind our field scouts and confirmed that Lygus were at ET at those sites.  We would now like to get the word out to consultants and producers alike.  It is very likely a few other area cotton fields are now at or nearing ET as well.  These two fields (two fields so far) are far from the majority.  Only through careful scouting were the problematic populations found.

A useable threshold for Lygus is 1 insect every 2.5 feet with a quick 10% increase in Lygus caused fruit drop, but we tend to start considering a spray when we find 1 insect every 3.5 feet with the associated fruit loss.  Normal plant fruit loss is currently picking up also as fields set more and more blooms to bolls so there is a need to make certain you are dealing with Lygus induced fruit shed.  A cotton plant will commonly shed some of its bolls is doesn’t think it will be able to support them later in the season for multiple reasons. This is quite common as it is impossible for a cotton plant to mature into harvestable bolls every square put on, especially this season with our fruit set riding so high.  Plant induced fruit loss tends to be limited to dime sized bolls, while Lygus can impact anything from squares to larger bolls.  Often a Lygus feeding “dot” or site can be found on the damaged squares and bolls just before they are shed.  If your fruit loss looks like it covers several different sized squares and bolls and a few are noted with the feeding “dots”, it is more likely insect induced than normal plant drop.  If that drop is more than 10-15% of the plants’ fruit and there is a Lygus every 3.5 feet or less, it is probably time to consider applying some insecticide.  Keep a sharp lookout for these insects to prevent them from causing your field yield loss!
Good Luck!                                                    Please call or come by the office if you have any questions.  Thanks!

        Kate                                                                                                                     Blayne

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