sciencetech-blog

comments

Saved? Scientists claim tomatoes grown amongst other vegetables could protected from whiteflies

It is a problem that has puzzled generations of gardeners - but keeping annoying pests away from prized tomatoes may in fact be very simple.

Academics have found that the whitefly, a devastating bug that weaken and kill plants, are easily distracted by the smell of other vegetables.

Simply mixing tomatoes in amongst other plants such as cucumbers or courgettes may be enough to keep the pests at bay.

Scientists at the University of Newcastle exposed whitefly to a heady aroma of watercress, watermelon, cabbage, cucumber, courgette and beans.

As a result, the insects struggled to attack tomato plants growing in a greenhouse.

Dr Colin Tosh, who co-wrote the study, said: 'It's like trying to concentrate on work while the TV's on and the radio's blaring out and someone's talking to you.

'You can't do it - or at least not properly or efficiently - and it's the same for the whitefly.

'Whiteflies use their sense of smell to locate tomato plants. By bombarding its senses with a range of different smells we create "sensory confusion" and the result is that the insect becomes disorientated and is unable to feed.'

Whitefly is a major worldwide threat to greenhouse crops and is traditionally controlled using chemical pesticides or natural parasites.

But the research has opened up the possibilities of an effective, organic way of battling the pest, both on an industrial scale and in amateurs' back gardens or allotments.

Like many pests, a whitefly feeds by pushing its long mouthpiece into a leaf until it reaches the nutrient-rich plant sap. In doing so it weakens the plant and leaves behind a sticky excretion that encourages the development of mould.

Pests struggled to get to the tomatoes hidden between courgettes, beans and cabbages

But locating the right plant cells is technically challenging for the insect and can go wrong if it is distracted.

The study, published in the journal Agronomy of Sustainable Development, shows that the 'confusion effect' of an array of vegetable smells can be used to protect a single crop.

It distracts the bug long enough for the plant's own defence mechanism to kick in, producing a chemical that makes it and neighbouring plants unpalatable to insects.

Dr Tosh said: 'Because the effect is temporary - we saw it last no more than 15 hours - it's unlikely this method alone could be used to control crop pests. But this is an easy and safe way of buying the plants time until their own chemical defence mechanisms kick in.

'Used in conjunction with other methods, sensory confusion opens up a whole new area in sustainable pest control.'

The findings suggest there could be an organic way to fight pests on an industrial scale and at home

Co-author Dr Barry Brogan, also from the University of Newcastle, said: 'Plants talk to each other when they are under attack, producing chemicals which warn other plants close by of the threat. At the same time, they produce a chemical which is unpleasant to the predator.

'But this response doesn't happen immediately, so if we can confuse the insects long enough to give the plants time to defend themselves this may go some way to reducing crop losses.'

The authors think that the same technique could be used to battle other pests, such as blackfly and aphids, and the principle should apply to vegetables other than tomatoes.

Dr Brogan said that the team is talking to industrial growers about developing an organic spray which pumps the scent of other vegetables into a glasshouse.

But for amateur growers, simply planting vegetables among other varieties should do just as well - whether in a greenhouse or in the garden.

'Mixing things up should really do the trick,' he said.