"Cavitation" In Cotton
We are seeing some “cavitation” in certain fields this year. There were originally several theories as to why “cavitation” occurred. Many thought that it was due to a break down or cavitation in the xylem, which would deny water to the developing boll. That is why it is often referred to as “cavitation”. We no longer believe this is true and “cavitation” is probably not a good word to describe this phenomena.
We now believe that cavitation is not what causes this symptom. It appears that the abscission zone at the base of the peduncle is not well developed in certain varieties. We now believe that any stress that causes the plant to send a signal for the boll to abcise can cause this symptom. This could be pollination problems due to off label Roundup applications, shade, drought etc. The same stresses that would cause fruit to shed in most varieties will cause “cavitation” in others. A better term for this phenomena might be something like “boll stick”. Figure 4 shows the difference in the formation of the abscission zone in DPL50 and DPL90.
At this point in the season it is probably impossible to be totally sure why the boll stick occurred. Knowing the region of boll stick on the plant and the history of the field management and environment could help identify the cause.
Figures 1 through 3 show typical “cavitation” or boll stick symptoms.
Figure 1. “Cavitation” or boll stick.
Figure 2. “Cavitation” or boll stick over most of the fruiting zone.
Figure 3. “Cavitation” or boll stick close up. Notice the typical scar on the fruiting branch from the base of the peduncle towards the main stem.
Figure 4. This picture shows that some varieties, especially ones that have DPL90 in their background have a less developed abscission zone at the base of the peduncle. This makes them less likely to abscise or shed no matter what was the condition that induced fruit loss.
