  QCD strings originate from high-energy scattering in the form of Reggeons and
Pomerons, and have been studied in some detail in lattice numerical
simulations. Production of multiple strings, with their subsequent breaking, is
now a mainstream model of high energy $pp$ and $pA$ collisions. Recent LHC
experiments revealed that high multiplicity end of such collisions show
interesting collective effects. This ignited an interest in the interaction of
QCD strings and multi-string dynamics. Holographic models, collectively known
as AdS/QCD, developed in the last decade, describe both hadronic spectroscopy
and basic thermodynamics, but so far no studies of the QCD strings have been
done in this context. The subject of this paper is to do this. First, we study
in more detail the scalar sector of hadronic spectroscopy, identifying
"glueballs" and "scalar mesons," and calculate the degree of their mixing. The
QCD strings, holographic images of the fundamental strings, thus have a
"gluonic core" and a "sigma cloud." The latter generates $\sigma$ exchanges and
collectivization of the strings, affecting, at a certain density, the chiral
condensate and even the minimum of the effective string potential, responsible
for the very existence of the QCD strings. Finally, we run dynamical
simulations of the multi-string systems, in the "spaghetti" setting
approximating central $pA$ collisions, and specify conditions for their
collectivization into a black hole, or the dual QGP fireball.
