How to remove grey module when plot cluster dendrogram of WGCNA?

Question

[hsu]

I am using WGCNA to find co-expression gene modules. I found 18 modules. And then I plot gene cluster dendrogram. Here is my question: Half of my genes(almost 3000 genes) are not clustered into any of these 18 modules. They are defined as non-cluster genes, WGCNA tool put them into a grey module. How should I remove the grey module when I plot cluster deendrogram?

I use this function : plotDendroAndColors()

Thank you very much !