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Why we are seeing bacterial blight symptoms on resistant or immune (cotton) varieties?

Southwest Farm Press Daily

What is in this article?:

  • Why we are seeing bacterial blight symptoms on resistant or immune (cotton) varieties?
  • Bacterial blight update.
  • Disease appears to be affecting some partially resistant, resistant and immune cotton varieties in Texas High Plains.

Bacterial blight symptoms

Jason Woodward, Texas AgriLife

The moderate temperatures and wet conditions experienced throughout the High Plains from May to July were conducive for the development of bacterial blight (Fig. 1). An increase in the disease was observed across most of the region with observations of bacterial blight-like symptoms occurring on varieties that had previously been documented as being resistant or immune.

Initial ratings of a research trial near Plains, Texas, found the disease to be present in most all plots with disease incidence averaging nearly 25 percent. Upon closer examination, the ratings were found to be incorrect resulting from erroneous labeling of plots in the field. This is good news from a production perspective, as the updated disease ratings with correctly labeled plots immune.

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It is interesting to note that bacterial blight symptoms have been and continue to be observed on partially resistant, resistant and immune varieties (Table 1); however, the incidence of these symptoms did not intensify compared to what was observed on susceptible varieties.  We would like to apologize for the errant reporting of disease incidence ratings in early August; however, the fundamental question of “Why we are seeing bacterial blight symptoms on resistant or immune varieties?” remains.

Bacterial blight was also found on FiberMax 1830GLT in a trial near Amherst, and on FM 2484B2F from a field trial in Lubbock. We are continuing to examine the occurrence of disease and hope to better understand the factor(s) that have led to the development of bacterial blight on such varieties.

Currently, the implication of this aspect of the disease on yield is not known.  Boll infections (Fig. 1) were less common than the foliar symptoms.  It is likely that yield of resistant or immune varieties will not be affected; however, it will be important to document fields where bacterial blight was observed this year in order to monitor the disease in subsequent years.

We appreciate all who submitted samples for disease diagnosis.

Please contact Dr. Wheeler (806-746-6101; twheeler@ag.tamu.edu) or Jason Woodward (806-632-0762; jewoodward@ag.tamu.edu) with any comments, questions or concerns you may have about bacterial blight in cotton.

Figure 1. Bacterial blight symptoms on cotton leaves (top) and bolls (bottom).

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