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SEPTEMBER 1, 2017
During the period August 22-28 the cotton bollworm (CBW) trap catch numbers were steady to higher in comparison to the previous week at 3 of the 6 trapping sites with the highest number captured in Baldwin county.(See Table on page 2) The tobacco budworm (TBW) moth trap catch was significantly lower at 3 of the 4 trapping sites with Henry county having the highest number of TBW moths. Soybean looper (SBL) moth trap catch numbers were down by 24% to 49% at 3 sites but increased significantly in Elmore and Limestone counties.
There are still scattered fields of late-planted cotton that are at risk to losses caused by CBW, but most of the cotton is now at cut-out and is no longer being checked for insects. We have had one report this week of pod worms (=CBW) exceeding the economic threshold in double-cropped soybeans in Colbert county. Last year we had a few scattered soybean fields in Lawrence county with pod worms that required treatment during the first week of August. Populations of pod worms that exceed the economic threshold in soybeans tend to be very spotty. Soybean loopers are the main insect of concern this week for double-cropped soybeans in parts of North Alabama. The need to get the corn crop harvested and rains since August 30 have hindered looper applications. The velvetbean caterpillar (VBC) is now the predominant caterpillar pest of soybeans in central and south Alabama. The density of extremely small VBC larvae ranged from 50 to 70 per 3 row feet on untreated soybeans in test plots at the Fairhope research station in Baldwin county on 8/29. Up until this week a mixed population of SBL's and VBC 's have consumed 40% of the foliage in non-sprayed plots but now the looper numbers have declined significantly and VBC's are increasing. If these small VBC larvae survive the result could be complete defoliation. Based on our test plot results last year, if soybeans were sprayed with bifenthrin, Dimilin, Intrepid/Intrepid edge or Prevathon/Besiege on August 15th the VBC population probably will not cause much defoliation through mid-September.
The stink bug complex on soybeans is a major concern for late-planted soybeans in central and south Alabama. This week at the Prattville station when 8 unsprayed R7 stage soybean plots were sampled taking 10 sweepnet sweeps per plot (swept low and hard across 2 rows) the mean number of stink bugs collected per sweep was 1.65. The population consisted of brown marmorated stink bugs (70%, mostly immatures), red banded stink bugs (16.7% mostly adults) and southern green stink bugs (13.6% mostly immatures). Near this soybean test cotton bolls in unsprayed plots on the edge of the station and bordering a road had 93% punctured bolls. The brown marmorated stink bug was commonly observed in these cotton plots. The red banded stink bug is spreading across central and south Alabama. This pest has been reported this year in Pickens, Greene, Monroe, Escambia, Baldwin and Henry counties. It may be present in most counties from Tuscaloosa to the coast. Another mild winter could set the stage for serious problems with red banded stink bugs in 2018. The silverleaf whitefly is the major concern for cotton growers in the southeast portion of the state. One practice that has been shown to improve whitefly control is to add an oil or soap product to the insecticide and use higher volumes of water per acre to improve coverage.
Tim Reed, Extension Specialist, Entomology & Plant Pathology
Ron Smith, Visiting Professor (retired), ACES
Alana Jacobson, Assistant Professor,Entomology and Plant Pathology
Barry Freeman, ACES
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