David Kerns LSU AgCenter Entomologist and Interim Cotton Specialist
Cool damp weather has greatly hindered Louisiana cotton emergence and stand establishment. Some cotton has been languishing in the soil for 10 days with only 20% or so emerged. Many growers are beginning to wonder if they should replant. However, I would stress patience and give the crop 14 days and then make that replant decision. There are no hard and fast rules for making the right replant decision and circumstances are going to vary from field to field. When assessing whether to replant we need to consider plant stand density, stand uniformity, potential death of surviving plants, and the cost associated with replanting.
On 38-40 inch rows we optimally would like to have 25,000 to 50,000 plants per acre or 2-4 plants per foot; but if fairly uniformly spaced, we should be able to tolerate as few as 1.5 plants per foot and still not see a huge hit on yield, although maturity will be delayed. As mentioned stand uniformity is an important replant decision as well. Some skips can be tolerated as long as adjacent rows have healthy stands, but in areas were stand is inadequate across several or more rows, yield will be impacted.
Another complicating factor is the health of the surviving plants. Under the conditions where we see poor plant emergence (cool and damp), seedling disease and wireworm damage are much more prevalent and lethal. It’s a good idea to pull up a few surviving plants and examine the roots for disease. Unhealthy roots will have black water soaked or collapsed areas. Consider these plants as having a high probability of dying. Additionally, I suggest cutting into the stem’s vascular tissue lengthwise and looking for discoloration for further evidence of probably infection and death. Also take note of how the cotyledons look. Do they look healthy? Do they have holes from wireworm feeding? And do you see wireworms in the root area when digging up plants? Answering yes to any of these is indicative that further stand loss may occur.
Replanting costs money in seed, labor, diesel, etc. Fortunately the major cotton seed suppliers all have replants or “shared risk” programs. These programs generally cover the technology fees for the Bt and herbicide traits, but do not fully cover the cost of the non-traited genetics. Although there is a move towards an industry-wide standard, there are differences in the programs. If you decide you need to replant, you should contact the seed dealer from whom you purchased the seed. In turn they will contact the seed company representative and they will verify the need for the replant.
For more information or if you have questions or concerns contact David Kerns or Sebe Brown.
Dr. David Kerns Cell: 318-439-4844 Office: 318-435-2157
Sebe Brown Cell: 318-498-1283 Office: 318-435-2903