Hi, I tend to agree with the others as we have very definite red spider in the conservatory on a nectarine. But, as you are in a poly tunnel I wonder if it could be something else although can't suggest what, to be fair. Poly tunnels, well ours, gets very humid even with doors open, it's like a Turkish bath and red spiders avoid humidity as much as possible. I'd also be loathe to clear and leave said tunnel until the spring - clear out, fumigate, get the humidity really up and sow Chinese Cabbage, Pak Choi, December potatoes etc etc. Keep your eyes peeled too and spray with Neem Oil in water with a bit of Ecover or similar as soon as or before you see anything. What about cutting back some of the best peppers, potting them and taking outside. Bring them in when/if they survive and keep them through the winter? Can't waste a good poly tunnel for those expensive veg over the winter.