The fashion for collecting wild mushrooms began with celebrity chefs such as Antonio Carluccio, and has been encouraged by those with a revived interest in local food, such as Jamie Oliver.

This year's wet summer and mild autumn has produced bumper crops of colourful wax caps, common ceps and luscious chanterelles.

But this new generation of foodies and foragers are beginning to trample the forests and fields that feed them – as well as many animals and insects, warn those who look after the UK's woodlands and nature reserves.

Concern is particularly high at some of the country's best-known beauty spots, including the New Forest, Epping Forest, and around the North Downs hills and the Chilterns.

So serious is the problem in some areas that a few big collectors, found with bagfuls of mushrooms from one trip, are being prosecuted. In just one weekend earlier this month, forest managers reportedly confiscated 45kg (100lbs) of fungi at a site near London.

Conservation managers and organisations appear to agree that small-scale collecting for personal use is not the problem. The Forestry Commission and the National Trust organise courses to help people identify safe mushrooms and teach how to collect them without damaging the surrounding landscape. Crucially, collectors are also urged to leave enough behind for the deer, rabbits, mice and insects such as flies and beetles, which also feast on fungi.

Matthew Oates of the National Trust, which is one of the UK's biggest land owners, said: "If one or two people visit a place and pick a few, that's probably not much of a problem. But if a couple of people go there repeatedly, visit the same place and collect as many as possible for commercial gain, that could be a problem."

Not everybody is worried. Carluccio, who has written two books about his passion for mushrooms and presented a BBC2 series on the subject, still goes collecting for his family's use, and believes environmental fears are exaggerated.

Carluccio said that this year's bumper crop, and the parallel reduction in mushroom species that are not collected for eating suggest fungiphiles are not the problem. He also points out that once a mushroom cap is open it has released breeding spores, and that centuries of collection in other countries in Europe, such as Italy and France, have not appeared to lead to long-term damage.

"The mushrooms are there every year, so it's not true that picking mushrooms would destroy the place," Carluccio said.

The chef, who does not use wild mushrooms in his cafes and delis, believes there should be licences for commercial collectors to ensure they behave responsibly, as there are in many other European countries. "There should be more discipline in collecting: not trampling everything, not destroying everything and to be limited to what you can consume. But don't deprive people of the wonders of going to the woods for the mushrooms," he added.

Despite Carluccio's comments, there are plenty who are worried. The Royal Society for the Protection of Birds said commercial collecting was a growing problem on its reserves near London and other cities. The National Trust is also worried about commercial collectors, especially on the sites of special scientific interest (SSSIs) that it manages and warned that it is illegal to collect in protected areas. Several SSSIs are in the New Forest in south-west England, which is managed by the Forestry Commission, which reported that "fungi picking is becoming an increasing problem … with more and more large-scale, potentially commercial picking being observed year-on-year".

Perhaps one of the most visited SSSIs, is Epping Forest, on the north-east edge of London, where keepers report that illegal fungi picking has reached record highs this year. Individuals have been found with five bags full of mushrooms at a time, including poisonous species. This has led managers to suspect they are being collected commercially for sorting elsewhere. The City of London Corporation, which owns the forest, has already issued 20 formal warnings this year. It has successfully prosecuted one person and is currently prosecuting a further six.

"Fungi play a vital role in the ecology of all natural habitats," said Keith French, the forest services manager. "They are nature's recyclers, as they break down organic matter from plants and animals. Many creatures feed on fungi, and they are host to some rare invertebrates that are unique to these ancient woodlands.

He added: "We welcome people visiting the forest and admiring the many fascinating shapes, forms and colours the fungi world has to offer, but please leave them there for the next visitor and future generations to enjoy."

Collecting tips

• Some mushrooms are poisonous: only collect what you know is safe and always carry a field guide to be sure.

• Wildlife need mushrooms too: only collect what you will personally use (about 1.5kg, as a guide).

• Only pick from plentiful populations and do not collect more than half of any one species at a location.

• The bulk of the mushroom is below the surface: take care not to damage it or trample surroundings.

• Mushrooms reproduce by sending out spores when they open: do not pick until the cap is fully open, or after it is past its best.

• On private land and nature reserves ask for permission and advice before collecting.

• It is illegal to collect fungi on Sites of Special Scientific Interest (SSSIs).

For more advice, read Phil Daoust's guide to picking wild mushrooms

Sources: The Scottish Wild Mushroom Code, published by Scottish Heritage; and Forestry Commission