July 11, 2021

A cotton crop must be managed as plants go through several distinct processes that overlap during the season. Planting the seed and getting it to a stand is just the beginning. To have lint to harvest, we set squares, hold squares, set bolls, hold bolls and fill bolls, in this order. These events often happen at the same time, and each has a very different set of concerns. To successfully grow a high-yielding, high-quality cotton crop, each stage of plant growth must be successfully managed throughout the production cycle.

Setting and Holding Squares

Squares, or flower buds, signal the beginning developmental stages of the cotton crop. Squaring takes place approximately 35 to 40 days after emergence and continues through the season. Several factors can influence square-set in cotton plants.

Squares are mostly independent of the plant — they make enough carbohydrates to support themselves without being a huge draw on the plant. During periods of extreme stress (long, cloudy, wet periods, and periods of waterlogging/extreme drought stress) and during the very late growing season, however, some physiological square shed can and does occur. As farm managers, we rarely have control over most of these types of events, but here are some proactive measures we can take to protect fruit.

Manage Insect Pests

Squares on young cotton plants must be protected from various insect pests, including lygus bugs, fleahoppers and various worm species. Squares that are damaged by insects flare and are shed by the plant. Those squares have no opportunity to contribute to yield. A sound scouting program followed by timely applications of appropriate insecticides is essential in establishing optimal fruit load in cotton production.

There are two primary factors to consider when evaluating the insect status of the field:

  • Count insects and stage of development.

  • Count square retention.

Various thresholds exist for the insects that attack squares and fruit, and applications should be considered when thresholds are met. Decreases in square retention should be carefully evaluated to clearly define the causes. Plant stress and/or insect damage can both be at fault at various times through the season.

Managing Plant Growth

Plant growth regulators (PGR) are used to redirect energy from vegetative growth and make it available to other parts of the plant, including developing fruit. One primary benefit of this redirection is making more energy available to fruit, thereby increasing fruit retention. PGR effects are long-lasting in the plant, so starting early is essential and can help to manage aggressive mid- to late-season growth.

To really optimize PGR use, we must understand how each variety reacts to PGRs when applied. Some Deltapine® cotton varieties are much more determinate and thereby typically more sensitive to PGR applications than others. When growing less-sensitive varieties, many systems require very aggressive approaches to growth control if adequate results are to be obtained.

While there is no standard PGR approach for cotton crops, several factors are keys to success, including knowing varietal background; making applications starting at T8/9 nodes, even if at reduced rates; and reapplying as necessary based on field conditions and plant development.

Many other factors should be considered during the development of squares and fruit. Adequate fertility/irrigation, good insect control and timely defoliation can all aid in helping retain fruiting positions on Deltapine cotton varieties.

By Jay Mahaffey, Scott Learning Center manager and Bayer Science fellow

ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.

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