Cotton Defoliation Temperature Advisory

The aftermath of Tropical Storm Lee has brought cooler than average temperatures to many areas of the state.  Maximum air temperatures are predicted to be in the high 70’s and low 80’s through Friday while minimum air temperatures are predicted to be in the mid-50’s for that same time.  While moderate temperatures are a welcome sight following a long, hot summer, it would be wise to keep the forecast for the next few days in mind if you are planning on making a harvest aid application.

Thidiazuron only products (Freefall®, Thidiazuron 4SC®, etc.) in particular are especially sensitive to cooler temperatures.  While predicted temperatures are not cool enough to render these products totally useless, defoliation activity will likely be slower than when they are applied under warmer conditions.  Predicted conditions through Friday favor the use of products that are a combination of thidiazuron and diuron such as Ginstar®, Adios®, etc.  While caution must be exercised when utilizing these types of products when “normal” early September conditions exist, the diuron component of these products allows for maintained activity at lower temperatures compared to thidiazuron only products.  However, care must still be exercised when selecting rates of thidiazuron + diuron harvest aids.  Application rates greater than 1:32 should be avoided as leaf desiccation may result.  Addition of phosphate materials (i.e. Folex®, etc.) should also be carefully considered as they increase the potential for leaf desiccation when used in conjunction with elevated rates of thidiazuron + diuron.  If you choose to tank mix these products, adjust your thidiazuron + diuron rate downward accordingly to avoid potential problems.

For those who plan to apply Folex® + ethephon, you may consider adjusting the application rate of Folex® in accordance with current and future weather conditions.  If you have been using rates of 1:26 – 1:32 during periods of warmer conditions, application rates such as 1:16 – 1:21 will likely produce similar results while cooler temperatures remain.

Temperatures are predicted to begin increasing on Saturday after which time adjusting application rates back downward as appropriate will likely be necessary.  Mississippi State University in cooperation with the University of Arkansas and the University of Tennessee has developed the 2011 Mid-South Cotton Defoliation Guide.  The guide can be accessed by clicking the link below.  All information in regard to products and rates above and in the 2011 Mid-South Defoliation Guide is provided as a basic guide, use all available sources of information as well as personal experience when selecting harvest aid products and application rates.

2011 Mid-South Cotton Defoliation Guide