Reminiscing on 50 years in fruit growing, he described an automatic orchard tractor steering system called Autotrac he trialled at Highland Court Farm in Kent in the 1970s, based on a network of underground cables. "You could leave it to mow an avenue by itself," he said, but it failed when cables were found chewed by mice and voles, and was not pursued. "It's like a boomerang I chucked away and has now come back."
Several mechanical harvesters were tested in the USA, where Withnall visited to learn more about fruit industry technology. Professor Loren Tukey at Pennsylvania State University developed a machine to "finger" apples from tree wall-type rows, while Arnold Berlage at Washington State pioneered a "shake and catch" system similar to that now being employed in cider orchards.
Ultra-low-volume spraying has also been in use since the 1970s, when Withnall trialled it at Highland Court, but this has remained commercially available from its developer Micron, he said. He added that propagating an early shipment of Gala apple cuttings from New Zealand and then planting them was also among his "Eureka moments" from the same era. Despite his efforts here not being immediately successful, he said: "Gala went on to change apple growing in the UK beyond our wildest dreams."
He forecast that robotic harvesting arms now being trialled for glasshouse peppers "could lead to robotic harvesting hands in orchards in the next five years". But he added: "There is now no work being done on this in the UK."