RD Petroleum managing director Don Harvey said the Dunedin company's core business was supplying bulk fuel to the primary sector.
The company also operated fuel stations in predominantly rural areas that directly serviced those communities.
"Our business very much revolves around the activity level of our client base."
"If there is going to be something that reduces that activity, i.e. labour shortages, it will have an impact — if they are busy, so are we."
The company had already scaled back some activities, particularly supplying the tourism sector, but had not yet budgeted on any reduction in supply to the primary sector, Harvey said.
"Certainly, it's very concerning about what lies on the horizon."
Fruitfed Supplies national manager Duncan Fletcher said Fruitfed — the horticultural chemical supply arm of PGG Wrightson — shared the concerns of growers.
''We rely on clients being successful and having an income.''
The effect of any loss of harvest this season would roll on into the 2021-22 season, he said.
''Some of the producers we supply in the wine industry only come to us post-harvest.''
Timpack Industries Mosgiel branch manager Peter Dyer said the timber packing company served horticulture and to a lesser extent viticulture at the ''tail end of the season''.
In the predicted worst-case scenario of a 50% reduction in harvest it could mean the loss of three to four jobs at his branch alone, he said.
He estimated 25% of his business came out of Central Otago, but the company had branches across New Zealand.
"I'd say throughout the country it's going to be felt."
Transworld Roxburgh co-owner Geoff Smith said any loss in apple production would make a "significant dent" in his business.
That business was transporting the majority of apples produced on Central Otago orchards to cool stores in Dunedin before the fruit went to Port of Otago for export.
At peak season he ran three to four trucks between February and July.
Earlier in the season his work involved transporting packaging to apple and pip fruit producers.