"It's not the size that matters..."
Throwing more energy at a problem sometimes simply might not help. What matters are the means to do it, which would go into sci-fi and require some (or a lot) of handwaving to make it palatable to present-day readers.
Some examples:
* TV series "Stargate SG-1" explained it away with removing enough mass from a star to offset the gravitational/fusion balance so that the star blows up. Question is, wouldn't you have to remove that much mass that the fusion reaction stops?
* TV series "Star Trek: The Next Generation" features a device to "halt a star's fusion reaction". Now imagine it the other way round, to make the star burn up fuel for thousands or millions of years in a fraction of a second.
"But..."
Blowing up the star would not help. Rather it would make matters even worse. If your 'larvae' are resilient enough to survive their planet being blown into its consituent parts, follow me through the following scenario:
1. 199
By whatever means, the central star of the system goes boom.
2. The shockwave of the explosion expands with fractional-c, reaching the planet in the habitable zone any time between ten minutes or a hour
3. The neutrino emissions may alert the beings if they're sentient and developed enough. Since they don't seem to be a localized threat, they may very well be - so some could leave in time.
4. The shockwave would first strip away the atmosphere, then ablate the outer crust, the mantle, the core, and then blow the remains (the far side of the planet) to pieces.
5. And that could mean that parts of the crust which had been the shadowed side of the planet may still be in pieces large enough for the larvae to survive, if they can survive the rigors of space.
Now that gives me an idea for a spore-like lifeform that actually uses this as a means to spread out through the galaxy. Develop on a planet, 'do something' to blow up the sun, then ride out the shockwaves to another solar system. 99