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Strong Cotton Requires Solid PGR Management

With thousands of Deltapine® brand Bollgard® 3 ThryvOn™ cotton with XtendFlex® Technology acres planted this season, growers across the cotton belt are experiencing the outstanding performance against thrips. But with that control comes a healthier-growing plant, that reaches pinhead square rapidly there may be a need for early plant growth management.

“Most university cotton specialists do not recommend spraying ThryvOn Technology cotton for thrips, as we have seen this technology provide outstanding protection against this pest for three seasons across moderate to heavy pressure,” said Jay Mahaffey, Bayer science fellow and Scott Learning Center (SLC) manager. “What we see is the cotton plants not suffering significant damage from feeding thrips, which allows ThryvOn Technology cotton to grow faster and healthier upon emergence, oftentimes reaching pinhead square sooner than what we are used to in cotton.”

The results of the increased plant health and reduced thrips feeding on cotton plants with ThryvOn Technology are the developmental differences that manifest during early growth stages. Increased plant growth and accelerated, non-delayed development are the most common observations from the reductions in thrips feeding and damage. This often leads to the increased need for awareness in timing the first plant growth regulator (PGR) applications.

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“Our work at the Bayer Scott Learning Center has shown the early timings to be the most beneficial in starting PGR management off in the most ideal way,” Mahaffey said. “Optimal timing seems to be between 7 and 9 nodes (matchhead square stage) for PGR applications to begin. A couple of factors to consider include the facts that PGRs are active at dry weight concentrations and at least the PGR effect is long lasting in the plant.”

Starting early with less plant mass and accumulating PGR in the plants can often lead to better growth control during the later season. This is equally true in both ThryvOn and Bollgard 3 XtendFlex (B3XF) cotton varieties, depending on field conditions and varietal response. Fields with less-growthy varieties often require less intensive PGR management than do more growthy fields and varieties.

PGR application decisions require complex considerations of a variety of factors:

  • Field history.
  • Field health.
  • Varietal background/Response to PGR.
  • Predicted growth conditions.

“Each factor should be weighed against the need for increases or decreases in the intensity of PGR application,” said Mahaffey. “The two primary modifications of intensity can be in either increasing rates and/or changing the timing of the application(s) made.”

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For more information, check out Response of Deltapine® Brand Bollgard® 3 ThryvOn™ Cotton With XtendFlex® Technology Varieties to Plant Growth Regulator (PGR) Regimens (2022).

Plant Bug Management

As stated, local extension recommendations are central to Lygus plant bug management in both Deltapine ThryvOn Technology cotton varieties and B3XF cotton varieties. SLC evaluations have confirmed the following recommendations:

  • Timely and thorough scouting is essential to the success of any insect management plan.
  • As appropriate, sweep nets, visual scouting and shake sheet samples should be used in scouting.
  • As dictated by local thresholds, applications should be made when insect numbers exceed the locally recommended threshold. This includes both adult and nymphal plant bug numbers.
  • Large (over the threshold) numbers of migrating adult plant bugs WILL require treatment when thresholds are exceeded. ThryvOn Technology has little to no direct activity on adults.
  • The primary ThryvOn effect on plant bugs is directed toward developing nymphs. Significant activity has been observed on these stages. Control is not complete; scouting is still required, and applications will likely be necessary in some cases.
  • Mid to late season, some impact on adult numbers has been observed as reproduction from migrant adults is reduced in the field being managed.
  • Our experience at the SLC has been recording one to two fewer Lygus applications and some delay in timing those applications across most ThryvOn Technology cotton experiments.
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For more information on Deltapine brand cotton varieties, visit Deltapine.com.