Mustard Yellow Polypore

The fruit bodies typically grow in rows of horizontal platforms, which grow over several years and sometimes "smear" onto the wood. The caps are usually semicircular with lumpy margins, 2–15 centimetres (3⁄4–5+7⁄8 inches) wide, with zonate colouration ranging from dark brown to light reddish-brown or yellowish at the margin, which is up to 1 cm thick and velvety. There are 5–8 pores per square millimetre. The flesh is tough and corky. The spore print is whitish or yellow.

Similar species. Mensularia radiata, the alder bracket, is usually found on non-oak hardwoods; fresh specimens often exhibit white-tipped pores near the margin.

F.gilva is a plant pathogen that infects several hosts. It is occasionally eaten by the widespread American pleasing fungus beetle Ischyrus quadripunctatus.

In traditional Chinese medicine, it is used to treat stomachaches and cancer; polysaccharides isolated from lab-grown F. gilvus have been shown to inhibit the growth of melanoma in a mouse model.