GANGS of hunters are trespassing onto farmers land to go hare coursing.
The sport, where dogs are used to chase hares, is ruining farm crops across the district.
Police said there are around 15 cases reported in the Epping Forest District every month, but admit it is difficult to catch the culprits.
The gangs, who place bets on the sport, usually trespass on to land by foot or car in the middle of the night to carry out the activity.
Theydon Bois farmer Stewart Galloway said: "We are always affected by it. Just as you finish planting all the crops they come along and go all over the place and ruin it.
"They always seem to come at about two or three in the morning. I know that there's a lot of money involved and they go around in gangs."
Essex police believe many of these crimes go unreported and they are now trying to find out the extent of the problem.
Wildlife Crime Co-ordinator PC Andy Long said: "The people doing it are illegally trespassing so they cause damage to fences and gates when entering the land and they often drive across growing crops. It's also illegal to be hunting with dogs.
"If a land owner confronts them there is a chance they could be met with violence which has happened before.
"I am often told that farmers do not inform us that they are suffering with hare coursing as they believe we are not interested. But we are and this is a chance to let us know the real extent of the problem.
"The information obtained will help us correctly utilise resources to tackle the problem."
The police are distributing a leaflet to farmers in the district to find out the problems caused by hare coursing and encouraging victims to report the crime immediately.
Mr Galloway said: "I would always report it straight away. We don't like to see hares shot to be honest. And if you're not careful you get all sorts of people driving around your land."
But James Saward from Patch Park Farm in Abridge said he had not had any problem for years.
He added: "We haven't seen it around here for about ten years. It used to be a huge problem, but it's not anymore, I wouldn't be happy if it was starting up again."
To contact an Essex Police wildlife officer call 0300 333 4444 or email wildlife@essex.pnn.police.uk.
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