In the Dragonriders of Pern books, the dragon riders burn the Thread before it hits the ground, Ground troops with acid/flame throwers then kill any which does before it can burrow into the ground. In one of the books they state that something bad happens if the Thread is allowed to burrow deep in the ground, but I don't remember it being revealed exactly what. Does it continue its life-cycle there?

This is confusing with the later books, where Thread is implied to live quite happily in the Oort cloud far out in the solar system and its destructive effects when brought to Pern by a eccentric planet, the Red Star, are essentially accidental.

1 Answer 1


From the Wikipedia about Pern, the main concern appears to be agricultural. Once burrowed, Thread can make a vast portion of soil totally sterile, which is a grave concern without grubs in a mountainous environment such as the north continent:

Thread has no brain and is not sentient. The majority of Thread dies after landing, due to starvation. However, if Thread survives to begin its feeding cycle on the organic component of soil, the result is a burrow that multiplies extremely rapidly. A single burrow can devastate multiple square miles of land before perishing.

That is why the agenothree fertilizer behaviour is doubly beneficial: It favorise plant grows, and counter-balance the effect of the few burrows which could have been missed by the dragonriders before soil teams discover them.

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    In the original survey of Pern, the crew notices that there are large areas of bare land in the middle of vegetation. These are, of course, Thread burrows.
    – SaintWacko
    Commented Sep 12, 2012 at 12:50

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