Cleistocactus strausii
As a houseplant, the Silver Torch cactus is an easy to take care of so long as over-watering is avoided. To naturally simulate the porous effects of the sand in its native habitat, it's important to ensure that excess water will not pool in the soil, causing the roots to become water logged.
This plant’s native habitat does not have winter, but when temperatures drop to the low twenties, it can exhibit signs of tip frost. 
The Silver Torch cactus is most susceptible to 
mealybugs 
and spider mite.
Phytophthora megasperma
Water moulds in the "P. megasperma" complex can be found on a multitude of host plants, including many agricultural crops. It has been noted on soybeans, kiwifruit ("Actinidia deliciosa"), horse chestnut ("Aesculus hippocastanum"), hollyhock ("Alcea rosea"), asparagus ("Asparagus officinalis"), "Brassica oleracea", crops such as cabbage, cauliflower, safflower ("Carthamus tinctorius"), Port Orford cedar ("Chamaecyparis lawsoniana"), chickpea ("Cicer arietinum"), carrot ("Daucus carota"), carnation ("Dianthus caryophyllus"), eucalyptus ("Eucalyptus" spp.), walnut ("Juglans regia"), apple ("Malus domestica"), pines ("Pinus" spp.), stone fruit such as apricot, cherry, plum, and peach, Douglas fir ("Pseudotsuga menziesii"), sugarcane ("Saccharum officinarum"), and potato ("Solanum tuberosum").