by Jason Woodward, Associate Professor and Extension Plant Pathologist, Lubbock, TX; jewoodward@ag.tamu.edu

Stand establishment is a critical stage in maximizing yield and obtaining uniformity in maturity. Assessing stand establishment allows you to determine if your crop is growing adequately and may dictate subsequent management options. Historically, cotton producers would frequently utilize high plant populations and thin to a desired density after plants have emerged. Increased seed cost and the adoption of precision planters has resulted in producers utilizing lower plant populations. Cotton plants have the ability to compensate for neighboring plants to some degree.

In general, yield losses are not incurred if a final population of 1.5 plants per foot (on 40 inch centers) uniformly spaced is achieved. Optimal soil temperatures (>65 F) and a favorable forecast in addition to adequate moisture will promote rapid emergence. Several factors can affect cotton during the early developmental stages. Best stand establishment will be achieved when using high quality seed as determined by the warm and cool germination results. When planting in less than ideal conditions, it is important to utilize lower vigor seed. Furthermore, the application of irrigation to water the crop up may reduce soil temperatures more rapidly, thus slowing plant growth and favoring seedling disease. Soil temperatures below 50°F can have a detrimental effect on the germination of cottonseed causing chilling injury. Cotton is most susceptible to chilling injury as water is taken up (the first 2-4 days) and becomes less of a problem once the radicle emerges. Growth and development of roots and seedling emergence can be slowed in cool temperatures are experienced for an extended period. Symptoms of chilling injury may vary, but plants exhibiting symptoms have a shortened tap root, as the meristematic tissue in the root tip is killed, often resulting in a proliferation of secondary roots, commonly referred to as crow-footing. These plants will generally survive and secondary lateral roots compensate for this loss; however, they are more susceptible to water stress. Additional information on chilling injury can be found on the 2011 Cotton Resource DVD (http://cotton.tamu.edu/cottonDVD/content/cottondvd/General%20Production/scs-2005-17%20Soil%20Temp.pdf). Furthermore, the compromised root systems may be more readily affected by seedling disease pathogens. Rhizoctonia solani is capable of causing seed decay as well as a pre- and post-emergence damping off with seed decay and pre-mature damping off occurring when seed is planted into cool soils. Symptoms of seedling disease caused by Pythium spp. are similar to those caused by R. solani; however, the seed and radicle are very susceptible to infection. In older plants, infections by Pythium spp. are restricted to feeder roots. Both R. solani and Pythium spp. are capable of killing plants after they emerge. Thielaviopsis basicola, causal agent of Black root rot, attacks the roots and lower stems of pants infections, with disease being more severe under cool conditions. Infected plants rarely die; rather they are delayed in development exhibiting severe stunting. A swelling of the root cortex may also be observed. Roots of infected plants are black and rotted, but generally recover after soil temperatures increase. If you have any questions about the content presented in this article, contact Jason Woodward at 806-632-0762 or via e-mail jewoodward@ag.tamu.edu.

Associate Professor and Extension Plant Pathologist
Dept. of Plant Pathology and Microbiology
Texas A&M Agrilife Research
Lubbock, TX
806-746-6101
jewoodward@ag.tamu.edu