Growers have been asking me about at-planting insecticides and which option is best because seed companies want them to select seed treatments when they order and because of availability of one new seed treatment formulation.
To understand which at-planting option is best for your situation, first ask, “What is the value of an at-planting insecticide?”
At-planting insecticides are used primarily to control thrips. Thrips injure cotton by feeding on the growing points of seedling cotton, which delays crop maturity.
Early crop maturity helped reduce the impact of boll weevils and insecticide-resistant tobacco budworms. Eradication of boll weevils and extensive use of Bollgard cotton, however, have reduced the value of early crop maturity — easily seen by the success of Deltapine 555BR, a late-maturating variety. Deltapine 555BR can take advantage of Louisiana's extended growing season and produce high lint yields. That probably would not have been possible before boll weevil eradication and Bt-cotton.
There is still value, however, in controlling thrips. Several fields without a thrips treatment have suffered significant plant injury and stand loss as a result of heavy infestation. A relatively inexpensive seed treatment could have prevented the additional replanting expense.
There are several options for at-planting insecticide use in cotton for seedling pest control. The products most commonly used in Louisiana are Cruiser 5FS seed treatment, Gaucho-Grande 5FS (formally Gaucho 4FS) seed treatment, and Temik 15G. Cruiser and Gaucho use has expanded greatly since their introductions, primarily because of their ease of use and safety. Each product has its own unique qualities.
Cruiser 5FS seed treatment and Gaucho 4FS seed treatment are very similar. I consider the two treatments as equals, thus I have the same expectations for one as for the other. Both are very good at controlling thrips, seedling aphids and tarnished plant bugs.
A reasonable expectation for residual activity of both materials is about 14 days after emergence or about 20 days after planting. The residual activity gets the seedling plants through the window of susceptibility to thrips injury (three to four true leaves).
Gaucho-Grande 5FS is a change in the formulation from the previous 4FS formulation available for cotton. The 5FS formulation is likely the same formulation as the Gaucho 600, the product labeled for corn use and for use by the commercial seed treatment units for cotton.
One significant change with Gaucho 5FS is in the allowable rate per acre. The labeled rate of Gaucho-Grande 5FS is 2X that of Gaucho. So, Gaucho-Grande used at its labeled rate would be equivalent to using Gaucho at 16 ounces per 100 pounds of seed. Sufficient data is available to determine how the rate change will impact efficacy.
There are several different options for application of a seed treatment. I have not found there to be a significant difference among seed treated by the seed company (Deltapine and Stoneville), seed treated by local dealers and seed treated with a turn-row type treater. The comparisons have been with both Cruiser 5FS and Gaucho 4FS on both small-seeded and large-seeded varieties.
Temik 15G has been used for many years. Its use has declined recently with the introduction of Cruiser and Gaucho and will likely continue to decline as more seed treatment options become available. Temik 15G's activity is similar to that of Cruiser and Gaucho with the added benefit of nematode control. Temik also provides about seven days of additional residual activity beyond Cruiser or Gaucho.
I would suggest that if you are using Temik15G, consider increasing the rate to 5 pounds per acre. This rate will also help with nematode activity.
One additional product that should be considered is acephate seed treatment. Acephate seed treatment usually provides acceptable thrips activity for about seven days after plant emergence.
The acephate seed treatment option may be a good cheap alternative for cotton planted after about May 10. Normally, we do not experience any extended cool periods after May 10 and growing conditions are usually very favorable. If thrips infest plants after seven days there is a good probability the plants will escape significant thrips injury.
Finally, do not be afraid to try multiple options. I think it best to tailor product use by planting date. Early-planted cotton (April 1) needs a lot of help to get through the cool spells, slow growth, and extended periods of susceptibility to insects. Alternatively, mid-May planted cotton can grow so fast that the full program insect control program is often overkill.
Ralph Bagwell is a professor and Extension entomologist with the LSU AgCenter.