Crop trials have sparked fierce debate in Scotland
The attack on the oilseed rape at a farm near Inverness was carried out on Friday night and was the second such incident in less than a week.
The crops were attacked for a third time in the early hours of Sunday morning, following which campaigners said more than half of the crop had now been destroyed.
The five who appeared at Dingwall Sheriff Court on Monday had sentence deferred for six months after pleading guilty to vandalism charges.
MBE accused
Among them was Iona Henderson, who was made an MBE in the New Year Honours list for her services to animal welfare.
She runs a sanctuary at Munlochy, near the field where the trials are being held.
The others were Simon Cann, 21, of Lady's Walk, Inverness; Gillian Williamson, 46, of Strathpeffer; Rory McEwan, 40, of Oban and Tom McCaig, 21, of Bonawe, Argyll.
Honorary sheriff David Neil told them that the court recognised their motives but they had crossed the line between protest and criminal offence.
They were arrested after police spotted them in a field at about midnight on Friday.
A solicitor for the five said they had acted out of frustration at the lack of political action on the controversial crop trials.
Government stance
The crop was attacked for the first time in a week over the weekend of 20 and 21 May.
The other two incidents happened over the weekend of 27 and 28 May.
The Scottish Executive has refused to ban GM trials, saying it would be contravening European law if it did so.
After the attack on Sunday morning, the protesters said in a statement: "We have been forced to take responsibility for protecting the health and environment of our own community by the only course of action now open to us.
"Our action was peaceful and nobody was injured.
"That people are more afraid of GM crops than of being arrested by the police speaks for itself."