Cactus
Fungi, bacteria and viruses attack cacti, the first two particularly when plants are over-watered. Fusarium rot can gain entry through a wound and cause rotting accompanied by red-violet mold. ""Helminosporium" rot" is caused by "Bipolaris cactivora" ( "Helminosporium cactivorum"); "Phytophthora" species also cause similar rotting in cacti. Fungicides may be of limited value in combating these diseases. Several viruses have been found in cacti, including cactus virus X. These appear to cause only limited visible symptoms, such as chlorotic (pale green) spots and mosaic effects (streaks and patches of paler color). However, in an "Agave" species, cactus virus X has been shown to reduce growth, particularly when the roots are dry. There are no treatments for virus diseases.
Puya dasylirioides
Puya dasylirioides comes from 2300-3300 meter elevation, where the climate is cool all year. It has taken temperatures in the mid-80s (30 °C), but it's possible that it won't thrive in consistently warmer conditions, especially if nights are warm. It is said to have taken winter lows of 19 °F (-7 °C), and might even handle colder temperatures. It grows well in a deep pot in normal cactus soil that contains no lime. Water it deeply occasionally, and avoid letting the soil dry out completely. Some protection from strong afternoon sun might be needed in warmer climates. Over about 40% humidity is recommended.