White mold up main stem

While inspecting my plants in the grrenhouse I found what looks like white mold covering a fairly large area on the stem about halfway up the plant. Is this mold? if it is, is the anything I can do to kill it or stop it spreading or will I have to chuck the plant

get a fan and put it blowin on the plant.

you need more air circulation.

Thanks! should I try and wipe the mold off or just leave it how it is. I forgot to say im growing in the greenhouse, weather has been really shit last 7-8 weeks, to much rain cloud and humidity. I offten have to keep the windows closed to keep the rain out but the bad side is it keeps it really humid in the greenhouse, wonderfull for my watermelon plant in there, not so great for my weed plants!

keep as many windows open as possable. and get a fan on the plant if you can.

no need to wipe the sh#t off if you get good ventalation.