Virginia Cotton: Variety Choices – Worm and Weed Control Technologies

Cotton seedlings. ©Debra L Ferguson Stock Photography

This week, I continue thinking about cotton varieties, but in a different way than the yield and quality aspects. The other major component to consider for variety selection is related to the technology package that is offered. 

There are two schools of thought:  basically to pick all varieties with the same technology to simplify management or to pick varieties based on their performance. The top three varieties in the report card this year all have different technology for weed and worm control.

Here is a quick summary of available technology:

Worm Control – No big management or trip savings, you just have to know what to put in the tank.  Everything has either 2 Bt genes or 3 Bt genes.

  • All the 3 gene stuff is in the high 90’s (TL plus+, BG3 or WS3).
  • The BG2 and probably TL2 are still fair and last year offered 80% worm control with no insecticides. Prevathon/Besiege may or may not be needed in a Pyrethroid tank mix in 2019, depending on Bollworm intensity.
  • WS2 (333 is the last one remaining) is the lowest at maybe 60% worm control. Requires Prevathon/Besiege at the beginning of egg laying.

Weed Control – I think this is the place to camp out a little bit. Everything has RU and at least some Liberty tolerance.

  • PHY 333 is the only one with partial Liberty tolerance. Multiple Liberty sprays will reduce yield and make it a below average variety.Management requires the most use of Preemergence and residual chemicals. Brake + Cotoran for Ragweed fields or Brake + Reflex for Palmer fields is the Cadillac and makes sense for 333 in fields with resistant weeds. Use Valor in Burndown.
  • Stoneville varieties & DG 1702 have full Liberty tolerance, but NO AUXIN Tolerance through 2018 releases.
  • Deltapine, NexGen, and DynaGrow (except DG1702) have full Liberty and the auxin – Dicamba Tolerance called Xtend (X). This adds flexibility on burndown timing with Dicamba. There is zero cross resistance with 2,4-D and therefore these varieties are just as like any non-Enlist variety with 2,4-D contamination or Drift. Dicamba drift and contamination to non-Xtend cotton is less than 2,4-D drift to Non-Enlist Cotton, Dicamba drift is more concern for soybeans which show extreme sensitivity (like 2,4-D to cotton) and peanuts
  • All Phytogen varieties that end in a zero called Enlist varieties have full tolerance to Liberty and the auxin 2,4-D.This adds flexibility to burndown timing with 2,4-D.There is zero cross resistance to any other variety which will be very sensitive to drift or contamination. Soybeans and peanuts are not as sensitive to 2,4-D contamination or drift as non-Enlist Cotton.

So the dilemma with these herbicides is primarily based on drift to your own or a neighbor’s crops and primarily with the Auxin herbicides. While there are some advantages of picking all the same technology for reducing injury risk, there remains a little. The advantage of diversity is you can select varieties based on performance.

Cleanout of Enlist and Xtend Products is much better than the older 2,4-D products were. You have to pay attention to calm days, fogginess and inversions with auxin herbicides. The upcoming herbicide management newsletter will get into some more detail.

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