Control #168 was showing clear signs of an unidentified disease organism on 6 March 2010.

Plant had died and decayed by 26 July 2010.
(The partially excavated carcass is shown below).

Control #166 had also died of a disease when we visited in March 2016.
We suspect this may be a rot following damage by an insect such as the blue cactus borer
but we have not yet positively identified the organism that is responsible.

Here are some more images of #166 in 2016:

 

Control #148 was showing indications of a fungal disease on 10 March 2014.

 

Control #164 is infested with some sort of a scale insect. 10 March 2014.

 

And also on #180 in March 2016.

All of the above were in Jim Hogg County, Texas.