Bell, who tracks plant response to climate change, said flowers are blooming before there are any pollinating insects to germinate them.
She said: "Flowers are out but few pollinators are there for them. A lot of the trees we grow for fruit are flowering very early. For instance, the purple plum opened extremely early this year, in January. If that happens there may well not be enough pollinators around that you expect in plum, cherry and other crops.
"That means there might well be a need to artificially introduce pollinators into the crops, which has a knock-on effect into the wider countryside because if you introduce pollinators they could become a pest elsewhere. There are none that have been introduced worldwide that have had no impact at all."
Bell added: "Populations of all sorts of aphids and scales could increase because ladybirds are not there that early to keep the numbers down. Usually when we are trying to reduce use of pesticides to control insects, ladybirds are a great ally in that endeavour.
"This couldn't have happened at a worse time. Artificial control is being very extensively questioned. Huge movements are against it."
About the project, known as Kew 100 because it monitors 100 plants, Bell added that virtually everything is opening earlier and that flowering is a long way ahead.
"It's very clear a lot of species at Kew have moved forward in their flowering times since the 1950s and very many more since the 1980s. For many it is several weeks earlier in just 30 years, which is really very surprising."
Kew botanist Nigel Hepper began recording plant flowering times in 1952, work that Bell has continued. She said: "Very few people have long-term data but Kew has been monitoring this since the early 1950s. Others are only setting this up now. They don't have data to make comparisons, which is what matters."
This year "has come up with something a bit different", said Bell. Particularly in the South East, "many flowers are opening several weeks ahead of the first years of the new millennium".
She added: "The underlying change is due to climate change but on top of that in the past two years we've seen very peculiar early flowering. This year several species have beaten their previous records from last year."
These include snowdrops, the native daffodil and Pyrus 'Chanticleer', which opened on 16 February - two weeks ahead of its previous first-flowering date.
She added: "Last year was back to normal after April, but the first three months of the year have been exceptional. There is a very strong case to show flowering times have responded to climate change. It's hard to see this slowing down, let alone reversing."