How to Manage Pests

UC Pest Management Guidelines


Selecting a Planting Date

(Reviewed 5/13, updated 5/13)

In this Guideline:

To determine the best planting date to establish a healthy stand, use a 5-day forecast of accumulated degree-days (heat units) and on-site soil temperature readings. Good stand establishment requires sufficiently warm air (measured in heat units) and suitable field soil temperatures. Use the following guidelines for 5-day degree-day forecast plus field soil temperatures until an optimal planting date is determined.

Cotton planting 5-day degree-day forecast

March 10th is the first date available for planting in the San Joaquin Valley. It marks the end of the 90-day host-free period for the pink bollworm control program, but does not necessarily mark the ideal planting time. Optimal planting time depends on soil temperatures at planting and during the 5 days following planting. Cotton seed requires approximately 50 degree-days to accumulate in order to emerge when planted at an optimum planting depth. It is also important that temperatures be consistently warm and don't drop during the first 5 days after planting. To determine the ideal window for planting, start taking soil temperature readings in your fields on March 5 (see below) and follow forecasts from the Cotton Planting Forecast. Forecasts for the San Joaquin and Sacramento valleys are updated every day from early March through the end of April each year.

Use the following guidelines to interpret the 5-day forecast, also taking into account your field soil temperature readings:

  • 10 degree-days or less are unfavorable for planting.
  • 11 to 15 degree-days are marginally acceptable for planting.
  • 16 to 20 degree-days are adequate for planting.
  • Greater than 20 degree-days are ideal for planting.
  • Be cautious about planting if cooling temperatures are forecast over the course of the 5-day period.

Field soil temperature readings

Couple the 5-day forecast with soil temperature readings from a number of locations in your field. A soil temperature reading of 58° to 60° F, taken at 8 AM, is considered the minimum temperature required for good stand establishment, as long as the 5-day forecast predicts favorable conditions for the next 4 days.

To measure soil temperature:

  • Use a soil thermometer. A fast-response thermometer (standard or digital) allows you to take readings quickly.
  • Take soil temperatures at 8 AM.
  • Make measurements by probing the seed planting depth.
  • Take measurements in 6 different locations to get an average field temperature.

Many factors influence soil temperature. These include wet versus dry soil, bed orientation, bed type (flat versus furrow), and residue cover in reduced-till areas. Therefore, measure within a representative area in which you will plant.

Check the crop after planting. If cotton emerges in:

  • Less than 10 days, it is an indication of good germination and emergence with seedlings experiencing ideal daily temperatures of 5 or more degree-days per day.
  • More than 10 days, the plant has experienced less than ideal conditions and there is a likelihood that some chilling injury has occurred.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cotton
UC ANR Publication 3444

General Information

  • L. D. Godfrey, Entomology, UC Davis
  • P. B. Goodell, UC IPM Program and Kearney Agricultural Research and Extension Center, Parlier
  • E. T. Natwick, UC Cooperative Extension - Desert Research and Extension Center, Imperial County
  • D.R. Haviland, UC Cooperative Extension, Kern County and UC IPM Program
  • V. M. Barlow, UC Cooperative Extension, Riverside County and UC IPM Program

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