P-th powers in mod p cohomology of fibers

Let $F\hookrightarrow E\twoheadrightarrow B$ be a fibration whose base space $B$ is a finite simply-connected CW-complex of dimension $\leq p$ and whose total space $E$ is a path-connected CW-complex of dimension $\leq p-1$. If $\alpha\in H^{+}(F;\mathbb{F}_p)$ then $\alpha ^{p}=0$.