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Tuta on the move July 2nd, 2017 by

The tomato is a remarkably versatile plant, with a huge number of different varieties, most of which are easy to grow. It is a popular crop with many farmers, a reflection of the strong demand from consumers in many countries. But the tomato is also prone to many pests and diseases and physiological disorders. The tomato plant is closely related to the potato and both suffer from similar diseases, including late blight, bacterial wilt and a host of viruses.

Twine for tomatoes copyTomatoes tend to be grown in small plots or in polytunnels and glasshouses, so I still recall my surprise a few years ago when I saw my largest tomato field ever in Mato Grasso state in Brazil. Double rows of tomatoes several hundred metres long were planted on a gentle downward slope. A team of workers were tying the plants to twine stretched between large poles of eucalyptus set about five metres apart. A tractor stood by, ready to carry new poles along the rows

It was an impressive operation, though I worried about the efficiency of large scale production as I watched the workers working hard to remove vigorous weeds. I also saw a number of serious diseases when I walked a short distance along the rows. More recently, I came across more large fields of tomatoes in Kyrgyzstan, during a series of visits in Chuy district with Alieve Nur and colleagues. Alieve works for Ailana, a local food processing company that produces tomato purée and tomato juice and cans vegetables and fruit.

P1040311 copyAilana have 126 contracted out-growers, most of whom have started to grow tomatoes in the last few years. The fields were set up in a different way to those in Mato Grosso. The tomatoes were direct-drilled by tractor, rather than being planted out as seedlings. The method appears to work, though there were a few gaps where no seeds had been apparently sown – or had failed to grow. They were bushy tomatoes so didn’t need staking. Which is just as well, since the largest field I saw was 52 ha. Imagine a rough square with each side 700 metres long. It would take over 30 minutes to walk around all four sides.

The other unusual thing I noticed was the absence of any major pests and diseases and weeds. The tomato plants were only a month old so maybe this was too early in the season for infections and infestations to develop. Or maybe the crop had been treated with pesticides, though there was no direct evidence of this taking place. During my day out I was presented with odd bits of leaves that were drying out or showing minor damage. Nothing to worry about, I said. But when you have a large area of a valuable crop any sign of disease can cause anxiety and precipitate hasty spraying.

Damaged fruit cut open 3 copySo far Tuta has only been found in glasshouses around Bishkek. It is unclear whether it will cause as much damage in open fields as it does in enclosed spaces, where favourable conditions lead to rapid spread of the highly damaging caterpillars. Nor is it clear how a farmer with a 52 ha field is going to control Tuta. This is a huge area for putting out pheromone traps, for example, and an expensive task as well.

There is some hope that the long, cold winters may wipe out Tuta every year, though continuous production in heated glasshouses will provide a refuge and the insect has an uncanny ability to survive hard times and re-emerge to attack afresh. In the UK my colleague Martin McPherson suggested to me that the high risk of late blight in open fields discourages farmers from this method of production.

Demand for tomatoes is growing in Kyrgyzstan and the season is short, so it makes sense to maximize production from fertile soils in open fields. Water is freely available. Farmers will now be closely monitoring the current tomato harvest for Tuta damage. Fortunately, wholesale buyers of tomatoes, such as Ailana, are already thinking about how to help farmers cope with this new threat. For the many people with a small garden plot of tomatoes it’s less clear who will be giving them advice.

Reference

Esenali Uulu T, Ulusoy MR, Çaliskan AF, 2017. First record of tomato leafminer Tuta absoluta in Kyrygyzstan. EPPO Bulletin. doi: 10.1111/epp.12390

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