Terminating Insecticide Applications in Cotton

The decision to terminate insect controls in cotton can be challenging in some fields but a few basic considerations will assist in that decision.  When evaluating a field a grower must first identify the last boll population which will significantly contribute to yield (bolls which you plan to harvest).  In some situations the last population of bolls which you will harvest is easy to see (i.e. cotton which is loaded and cutout).  In others, such as late planted cotton, the last population of bolls you will harvest will be determined by weather factors (the last bloom you expect to open and harvest based on heat unit accumulation).  Once the last boll population is determined the boll development or approximate boll age should be estimated.  Depending on the insect pest, bolls are relatively safe from attack at varying stages of boll development.

The table below list approximate boll age in days which bolls should be protected for selected insect pests.  Cooler temperatures will slow plant development and subsequent boll age values may increase in such environments.  It is assumed that the field is relatively insect pest free when the decision to terminate insecticide applications for a pest is made.

Insect Pest(s)

 Approx. Boll Age (days)

Corn Earworm and Tobacco Budworm

18-20 days, bolls fully sized

Stink Bugs

25 days

Fall Armyworm

bolls near maturity

Foliage Feeders: (soybean looper, beet armyworm, southern armyworm)

bolls mature

Sucking Insects: (whiteflies and aphids)


(honeydew accumulation on lint)

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