Crop protection

Brassicas need fine netting to stop cabbage white butterflies laying eggs.
Very fine netting needed for leeks and onions if your site gets leek moth or onion leafminer.
Ditto for carrots against carrot rootfly.

Fruit needs bigger holed netting to stop the birds eating ripening fruit.

I use debris netting for cabbages - bought on ebay, and use fine veggiemesh/enviromesh for leeks and carrots. Search to find the cheapest you can for the size you need.

Cheap fruit netting from Wilko works for me 

the mesh size has to be less than 7mm to stop butterflies and be very fine eg enciromesh to stop carrot fly/leek moth.

If the holes are biiger they can fold their wings and walk through