It is estimated that thousands of people illegally foraged for mushrooms in Epping Forest last summer as eight people are fined for the offence.
Head forest keeper Keith French said he and his colleagues regularly found people with large bags full of fungi, with the High Beech area worst affected.
The practice is banned as the forest is classified an area of special scientific interest, with many different varieties which could be threatened if regularly foraged.
Landowner City of London Corporation said it had been one of the worst years for the illegal activity.
And Mr French said he regularly witnessed large groups of people gathering to forage.
“We could have prosecuted thousands of people this summer. There were so many people picking mushrooms every single weekend,” he said.
“We try and talk to people and tell them that nothing can be taken from the Forest.
“It varies each year as if we don’t have the weather then the mushrooms will not grow.”
On Tuesday eight people were found guilty of breaking the bylaw by picking mushrooms.
Those fined £230 after pleading guilty were Ewa and Marek Krupka, of Vicarage Road in Leyton, Jadwiga Milo, of Woodland Way in Enfield. Aga and Maksymillian Kasprowicz, of Theobalds Lane in Waltham Cross, and Maciej Dolega of Sandhurst Road in Enfield.
Peotr Jaworski, of Leyland Road in Lewisham, and Tomasz Lis, of Cravan Park Road in Haringey, were convicted in their absence and each fined a total of £300.
Seven more people have been charged and are yet to stand trial.