May 17, 2010
Current cold air and soil temperatures can cause problems for new stands of cotton, according to Terry Pitts, Oklahoma State University Extension integrated pest management specialist.
Pitts recently addressed cool weather issues and early cotton insect problems in a report that can be found online at the NTOK Cotton website, ntokcotton.org.
"We are seeing some fields with fully emerged cotton and some that are just breaking the soil surface," Pitts said. "Some growers are asking about stands and what to do. If you see roots with big shanks or swollen areas or dead growth tips, then cold chilling has occurred." That cotton was probably planted between May 2 and 4."
Pitts suggests that growers to check comments in a May 6 newsletter at the above website.
"In addition," he said, "cold chilling makes the plant more vulnerable to disease, so a higher incidence of disease may occur on cotton planted before and after the dates listed here. The plant can go ahead and grow but will have a root system with less than desirable growth."
Pitts said decisions on replanting cotton should be based on seedlings with no cold chilling. "If a field has escaped that type of damage but had poor emergence due to crusting or other physical issues, it is generally acceptable to have a stand of only two plants per foot of row on 40-inch spacing.
“With current forecast, plantings after May 15 should be fine as no nighttime temperatures below 60 degrees are predicted. Also, historical temperature data show average lows do not occur beyond this date."
With some fields varying in emergence date, Pitts said thrips activity needs to be monitored on a regular basis. Heavy thrips migrations are currently occurring on border crops and where weeds dry down and mature. Prolonged migration can occur for fields next to wheat and pastures.
“Keep a careful watch on these areas,” Pitts said. “Fields like this that were treated with an at-plant systemic or seed treated insecticide may show signs that residual effect is wearing off.
These fields need to be monitored closely as heavy infestations may destroy plant terminal buds.”
Treatment is advised when the number of thrips averages one or more per true leaf. “Be careful to watch fields where plants are struggling,” Pitts said. He said Orthene or Bidrin could be used and will tank mix well with glyphosate. “When scouting fields, remember thrips and wind damage can be confused,” Pitts said. “An insecticide is rarely justified if plants are at the five to seven true-leaf stage or when plants begin to square.” Pitts works at the OSU Southwest Research and Extension Center, in Altus, Okla. He can be reached at 1-580-482-8880 or 580-318-3121. His email is [email protected].
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