The fuzzycotton-looking thing growing on your prickly pear is not a fungus at all.They are a small insect of the Coccidae scale family known as cochineal scale.These scales infect several native species of cacti usually in the opuntia family, such as Santa Rita ( purple prickly pear) , Engleman prickly pear, and several types of cholla. Although they look awful, they do little harm to your cacti and can be washed away with a high-pressure nozzle from your hose. Use of a pesticide to remove the bug could cause more damage to your prickly pear than the bug itself.    According to “Red Scales in the Sunset*”, at one time this scale insect was the most desired export from America next to gold.  If you crush these bugs, they will exude a maroon-purple liquid.  The dye made from this scale was more intense than any scarlet color of the old world. When the Spaniards arrived in Middle America they were amazed by the rich scarlet-red color of cochineal. In the 1500’s Spain established a monopoly on its trade. Small landowners producing cochineal became wealthy.  Textiles dyed from this insect became the rage in Europe.  Export demands grew and it wasn’t until 250 years later, in the 1770’s that the French broke Spain’s monopoly by smuggling cacti containing cochineal to Haiti.  Later production spread to other countries that could successfully sustain the opuntia cacti and its insect host. The pigment of this dye became a great source for food coloring.  Little did consumers know that when they were biting into sausages, shrimps, pies, and candies they were actually eating these fuzzy little creatures.  Even cosmetics, such as lipstick and rouge contained cochineal scale.  With more and more research indicating that red dye #2 and red dye #40 may be carcinogenic, cochineal is being reconsidered as a safe food coloring for consumer products.   So the next time you apply lipstick or bit into a bright-red maraschino cherry, you very well could be consuming the pest that is plaguing your prickly pear. *botgard.ucla.edu/html/botanytextbooks/economicbotany/Cochineal