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Thursday, May 30, 2013

Early Season Thrips


          Thrips pressure in the area is higher than I have seen in several years and they are rapidly moving into cotton as it establishes.  At this early stage, predators are a little slow in following the cotton migration. 

Adult thrips are straw colored insects 1/12 to 1/16 inch long.  The wings are fringed and held flat directly over the body when at rest.  Immature thrips look somewhat similar to the adult but have no wings and are somewhat lighter in color.  All thrips have rasping mouthparts which include a single mandible which the thrips uses to scrape and jab host plant tissue.  The thrips then consume the resulting ‘bleeding’ of plant juices.  Thrips often feed in the more sheltered and tender terminal or growing point of the cotton plant requiring very close inspections to acquire an accurate population count.  The ensuing damage causes scaring and malformation of the young leaves at a time when plants need healthy leaves for energy and a good start.  In the worst cases heavy and un-checked thrips damage can become severe enough to damage the terminal and delay squaring for several weeks. 

            Economic threshold (ET) for thrips remains at one thrips per true leaf stage, but there are multiple factors to consider in conjunction with that threshold.  The presence or absence of thrips larva should represent the primary additional consideration.  The presence of thrips larva indicates that the thrips are reproducing in that field and will be there causing damage for some time.  Some other factors include the recognition of light thrips damage, plant stage, and predator populations.  Thrips are one pest producers may want to consider treatments for before thrips reach ET if reproducing populations are confirmed.  Because thrips can move and reproduce so rapidly, thrips can cause serious damage faster than timely applications can be made.

Thrips pressure is progressively higher as we move north across Hale and Swisher Counties.  Our lowest thrips pressure area so far is in southwestern Hale.  Here we are still finding thrips at or above ET.  Cotton planted in dry wheat stubble that have been able to establish a stand, regardless of location, has so far shown the lowest thrips numbers.  Seed treatments and in-furrow insecticide treatments are showing good control for the dollars spent this season.  We have found little or no reproduction in these preventatively treated fields yet but, overwhelming numbers of adults are moving in causing light to moderate damage before being controlled.  I would recommend vigilance in the scouting of these fields for early thrips damage.  If producers will already be treating these fields with herbicides for weed control this week, they may want to consider adding a treatment for thrips to aid the preventative control measures.

Cotton fields with no preventative thrips control applied need to be scouted very quickly.  These fields might be at risk of developing serious and economic thrips damage much earlier than normal this year.  In many of these cases, thrips will need to be controlled as soon as possible. 

Please call or come by if I can help in any way,

Blayne

 

 

 

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