The trustee of a communal vegetable garden on the Isle of Wight has been jailed for at least 25 years after murdering a fellow project worker by attacking him with a chainsaw and strangling him.

The relationship between Jonathan Stasiuk, 60, a chef, and his victim, Gerry White, a 73-year-old publican, turned sour following seemingly trivial disagreements over money, the dumping of rubbish and a delivery of logs.

In the days before White’s death on 27 May, Stasiuk messaged friends saying: “Tomorrow I go to war,” and mentioned using a chainsaw.

The men were trustees of Lake community gardens in the village of Lake. After attacking White with the chainsaw, which is understood to have come from the garden’s clubhouse, Stasiuk strangled and smothered him, screaming: “Die, bastard, die,” Southampton crown court heard.

Gerry White, 73, who was murdered by Stasiuk. Photograph: Hampshire Constabulary/PA

Jailing him for life, the judge, Christopher Parker QC, said Stasiuk had intended to cut off White’s legs with the chainsaw, but the device cut out, leading him to strangle his victim and then smother him to ensure he was dead.

The judge said: “You had obsessed over your perceived although relatively trivial grievances that may not have any foundation whatsoever, to such an extent that you allowed them to build up into a form of hatred.”

In a victim impact statement read to court, White’s widow, Lee White, said: “Losing my husband under such horrific and unbelievable circumstances has led to major shock and anxiety. Knowing what he went through is hard to bear, life has changed and cannot be normal again. I have underlying sadness for Gerry but also fury and anger too. I find myself trembling and my teeth chattering. I have bad dreams and a feeling of fear and insecurity.”

The victim’s son, Desmond, said: “Dad was too generous and accommodating to the wrong people. People often took advantage of him.”

Jo Martin QC, defending, said: “Mr Stasiuk knows what he has done. He struggled to comprehend his actions, struggled to come to terms with the madness of those few moments and he is appalled at the consequences of what he has done.”

Stasiuk, who had worked in White’s pubs, helped look after the 16-acre “wellness” garden.

Matthew Jewell QC, prosecuting, said Stasiuk had a list of complaints against White. “Stasiuk harboured a growing sense of grievance and formed a strong belief in his position. Their relationship began to go sour for a number of reasons,” he said.

“There was an accusation made against Stasiuk’s partner about £25 transport costs owed to her; there was a dispute about logs being delivered to Mr White’s pubs that were apparently damp; there was an issue about plants. Rubbish appeared on the site and it appeared to Stasiuk that Mr White was using it as some kind of dumping ground.”

After the attack, Stasiuk called police and told the operator: “I’ve just murdered someone.”

Jewell said: “He told police where to find [White’s] body and said the murder happened 20 minutes earlier. He gave a full account over six interviews and told police officers he attacked Mr White with a chainsaw and then by strangling and smothering him until he believed he was dead.

“Stasiuk explained it was the result of a growing and festering dispute that had led to his actions on that day.”

Stasiuk, from Sandown on the Isle of Wight, had denied murder but admitted manslaughter on grounds of diminished responsibility. He changed his plea to guilty of murder as the trial neared an end.