Farmers need to first and foremost examine their yield-limiting factors when it comes to selecting cotton varieties.
So advises Guy Collins, North Carolina State University Extension cotton specialist, who emphasizes that water is still the No. 1 limiting factor for most cotton farmers. Other yield limiting factors vary from field by field and may include weed control, nematodes, plant growth and realistic yield potential.
“We need to be very careful with field-by-field observations and make our decisions based on that,” said Collins at a N.C. State cotton production meeting in Clinton Feb. 20. “Rainfall, soil moisture, soil type, etc. can drastically influence which one of those fields is going to yield higher or lower, much more than just variety.”
Because of this, Collins encourages farmers to look at replicated variety tests, both on-farm trials and OVTs (Official Variety Trials) when making cotton variety decisions. Data from replicated trials is valuable because varieties are compared side by side under the exact same growing conditions.
“It’s important to look at multi-location data and multi-year data. Every year is a little different. Location is important. Your natural instinct is to look at the results from a trial that is right at your back door. I encourage you to take a regional approach,” Collins stressed.
“Stability is still the best predictor of performance,” Collins said. “Every variety can win or lose a trial. No variety wins them all. What I like to identify is how often or frequently a variety can perform at or near the top and that gives you an idea about how well it’s going to perform across soil types, planting dates, rainfall patterns etc.”
And as he has at previous cotton meetings and field days since he returned to North Carolina in 2015 from the University of Georgia where he was cotton agronomist, Collins emphasized the importance of planting multiple varieties.
“No matter how stable a variety is, they all have a weakness,” he said. “The best way to find that weakness is to go and plant your whole farm to one variety. You’ll find it real quick. Therefore I always encourage you to plant multiple varieties.”
Pointing to last year when cotton planting conditions were poor across most of North Carolina throughout the season, Keith Edmisten, Collins’ fellow Extension cotton specialist encouraged farmers to turn to N.C. State’s internet cotton portal where planting conditions are rated as poor, marginal, good or excellent, depending on weather conditions. He said this is valuable for determining when to plant.
“Usually in the planting season from the middle of April to the end of May over half the time conditions are rated good to excellent. This past year there were not dates that were rated good to excellent,” Edmisten explained. “What is more typical is to go into decent conditions then bad conditions then back to decent conditions again.”
Edmisten said it is important to understand the physiology of a cotton plant and remember when it most sensitive to chilling and plant accordingly. Chilling injury can range from dead plants to seed that sprouts under the ground and never makes it up to slow growing cotton.
“As long as it’s dry, cotton can stand cool temperatures. It’s when cotton takes its first drink of water when chilling injury can occur. That’s the most sensitive time for cotton seed and it is pretty sensitive to chilling injury,” Edmisten explained.
For example, if a cold snap forecast for the first of May, farmers may want to slow down or stop planting for a couple of days before the cold front arrives. Edmisten advised farmers to turn to the cotton portal and not plant when conditions are rated as poor or marginal.
Edmisten encouraged farmers to find out the cool germination of their cotton seed. “A lot of the time you can get that information from your dealer or distributor. If they don’t have it, find your lot number and call the company,” he advised. “One cool germ is 68 and one is 80 and the one that is 80 is the one you want to plant when you have challenging conditions.”
In the meantime, Dominic Reisig, N.C. State Extension entomologist, cautioned against over spraying for plant bugs and to treat for plant bugs only when needed.
“One of the things we’ve been seeing is an increase in plant bugs across the state. In the Northeast, some fields are being sprayed five or six times. And they need to be sprayed five or six times. But the problem with spraying for plant bugs is we are knocking out beneficial insects. Knocking out beneficial insects creates the perfect environment for bollworms.”
Still, in northeastern North Carolina where plant bug pressure is the worst, spraying multiple times has paid off. Reisig encourages farmers to spray for plant bugs using the extension-recommended threshold. Last year, when plant bug pressure was particularly high, it paid to spray for plant bugs early.
“There is good rationale for spraying early. Plant bugs like to feed on squares,” Reisig said.
He advised against making automatic applications for controlling plant bugs. “If we don’t time it right, we're not really making ourselves a whole lot of money and we may be creating problems for bollworms later on in the season,” he explained.
N.C. State has made some changes to its insecticide recommendations this year. The university recommends farmers rotate their insecticides.
“One of the changes were making is you can probably use a pyrethroid unless there is resistance. If there is resistance in the system, you probably need to add Orthene,” Reisig said.
“The other thing we need to do is tank mix Diamond when we have heavy pressure. Diamond is an insect growth regulator and is only active on the immatures. Diamond has been shown to extend the spray intervals. When Diamond is used, instead of spraying instead of spraying five times you may get away with a two- to three week period where you don’t have to spray.”