WSGA was involved in the consultation about the road, which if improved would have given better links to more Horticultural Development Areas in West Sussex.
WSGA planning consultant John Hall said: "WSGA is very disappointed to hear the news that the proposed improvement scheme to the A27 at Chichester has been cancelled. WSGA is writing to Chris Grayling (Transport Minister), asking him to reconsider his decision."
Growers in the area include Langmeads, Barfoots, Hall Hunter and Tangmere Airfield Nurseries.
NFU president Meurig Raymond has also written to Grayling "to express my extreme concern over learning that Highways England has decided to cancel much needed improvements to the A27 Chichester Bypass.
Raymond added: "The Chichester Plain is an area of national importance for horticultural production, producing over £1billion of food and plants each year and employing over 8,000 full time workers. Horticulture is the largest industry in the Chichester area and is entirely dependent upon the road
network to service the high value protected cropping and packing installations in the local area.
"A recent Transport Assessment shows that the local horticultural industry generates over 1,000 goods
vehicle and 400 tractor movements per day. The vast majority of these movements use the A27.
Delays in improvements to the A27 are causing serious problems for the daily transport of fresh
produce from the Chichester area to customers nation-wide. If the situation is not improved and
transport becomes more unreliable, we are concerned that the retail customer base may look
elsewhere, possibly overseas, to source their future supplies of fruits, vegetables and garden plants.
"This would be a great shame and a serious loss to the industry and the national economy. It is essential that an improvement scheme is brought forward without further delay, and I would urge
you, with all sincerity, to reconsider your decision and push on with the much needed improvements to the A27 at Chichester."
Government-owned Highways England said Grayling had written to it "instructing us to stop work on the A27 Chichester Bypass major improvement scheme", following a consultation.
Chief executive Jim O’Sullivan said: "We are obviously disappointed at this decision as the improvement would have brought significant strategic benefits to the region.
"But any improvement had to be right for Chichester and there was no overall consensus. We will continue to work with partners to monitor the route’s performance and to carry out any short term measures we can to help road users, the local community and the region."
West Sussex County Council leader Louise Goldsmith said: "We are naturally deeply disappointed with the Secretary of State’s announcement but we are doing all we can to persuade him to reconsider his decision given the evident need of investment for the infrastructure of our county.
"The cancellation means that the dreadful congestion experienced by motorists every day on this road will now only get worse. This is not only felt especially at peak times, but also on the alternative routes used locally by motorists avoiding the A27."
The Road Haulage Association deputy policy director Duncan Buchanan said: "Pressure on the local road system is unsustainable and this scheme must be re-opened immediately.
He added: "The RHA believes people and businesses need to have confidence that commitments to transport schemes by Government are real, and will not be simply dropped when difficult or seen as controversial.
"Reviewing a proposal that is locally controversial is reasonable, but total cancellation as done here and passing the buck onto local authorities for committed investments on the national Strategic Road Network is not acceptable. Imagine if this approach was taken on HS2 or development.
"The RHA is calling on the Department for Transport and Highways England to reopen the programme immediately and to consider all options. This must include the northern route options, that Highways England unreasonably dropped from the 2016 consultation, and which seems to have contributed to local discontent."
The RHA believes that investment in the road network is essential for the economic well-being of the UK, targeted and effective road infrastructure investment will improve UK competitiveness. The long term under-investment in local and national roads has undermined UK productivity and now contributes significantly to congestion and local air quality issues.