Varroa induced brood break?

[The Poot in Somerset]

I have a colony which was strong after combining in July and continued strong through August. Varroa checks showed minimal drops. Then in early September varroa numbers increased hugely.
Through September the colony reduced down to less than four frames of brood and I started to really worry. I assumed the queen was failing.
I read JBM's thoughts about brood breaks in September and decided not to intervene / cull / requeen.
The colony was double brood and the top box ended up 100 percent honey, the brood being in the Lower box. They didn't need feeding, but I experimented with syrup feeding mid September and vaped through September.
The colony has suddenly got into gear and from
"reading" the inspection tray, has expanded significantly.

Can a heavy varroa load cause a queen to stop laying?

 

[Erichalfbee]

Did she stop laying or did the varroa kill lots of bees till you intervened with your vaping? The latter I would hazard

 

[The Poot in Somerset]

Hi Erica,
I think she stopped laying. The varroa drop seemed to increase significantly as the amount of brood dimnished.

 

[Erichalfbee]

Hi Erica,
The varroa drop seemed to increase significantly as the amount of brood dimnished.

It would.
More varroa are phoretic
That’s why oxalic performs best when there is no brood