Forcing unbalanced complete bipartite minors

Myers conjectured that for every integer s there exists a positive constant C such that for all integers t every graph of average degree at least Ct contains a Ks,t minor. We prove the following stronger result: for every 0 < ε < 10−16 there exists a number t0 = t0(ε) such that for all integers t ≥ t0 and s ≤ εt/ log t every graph of average degree at least (1 + ε)t contains a Ks,t minor. The bounds are essentially best possible. We also show that for fixed s every graph as above even contains Ks + Kt as a minor.