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