The tomato industry is moving closer to having several new options for controlling Tuta absoluta infestations, integrated pest management consultant Rob Jacobson has revealed.
Speaking last month at the annual British Tomato Growers Association conference, Jacobson said trials led by the Horticultural Development Company and the Food & Environment Research Agency - as well as trials and practices being carried out on the pest in other European countries - were leading to the discovery of more effective chemical and biological control options for growers.
For example, the chemical spinosad - the active ingredient in Conserve - has had positive results in four trials, applied to the crop using irrigation. This method is less harmful to the glasshouses' beneficial insects than spraying, said Jacobson. But he added: "We are having difficulty agreeing a new dose rate with the (pesticide) authorities. Hopefully we can do this in time to do more trials this winter."
The industry would benefit from being more proactive to get the product's use rates increased, he pointed out, because the pest, first spotted in the UK a few years ago after it came over from southern Europe, is here to stay.
"The pest is well suited to northern Europe with its optimum (breeding) temperature being 19-23 degsC. Its development slows above 25 degsC, which is consistent with observations made in Italy." He told Grower after the conference: "We have had one very serious problem this year in a glasshouse so we need a campaign."
In southern Europe, Dupont's product Rynaxypyr (chlorantraniliprole) is showing promise and Jacobson said it is possible that UK growers might be able to get some sort of extension of authorisation.
Mating disruption techniques that saturate the air in glasshouses with a sex pheromone that confuses males are also in development. Jacobson said while they have proved to be prohibitively expensive so far, Japanese firm Shin-Etsu has submitted a registration dossier to get such a product approved. "This method will therefore become more cost-effective over time," he forecast. "It's something for the near future."
Meanwhile, trials are underway in Italy to establish the full potential of a larval parasitoid Necremnus artynes that is indigenous to the UK. Jacobson described it as an exciting additional biocontrol for the future.
Growers who establish their primary biological control methods at the start of the growing season will reap the benefits in the summer, stressed Jacobson. He advised them to introduce predatory bugs as early as possible, based on the way that Tuta populations fluctuate throughout the year. They should then top up with a second line of defence - for example, using chemicals and nematodes.
An end-of-season clean-up is the most important part of the whole programme, he warned, because green waste harbours pests that can spread around the glasshouse if it is not disposed of carefully.
The main biocontrol available to UK growers is the predatory bug Macrolophus, released into the glasshouse at the start of planting. "In cases where it wasn't used, the spread of Tuta was awful," said Jacobson.
"All tomato growers should be monitoring for the pest by now and if they find it on their traps and they know it's in their crop, they should be starting to take measures to suppress it."
- The Tuta absoluta moth is just 6mm long.
- It can lay up to 260 eggs on the surface of plants.
- The young caterpillar can be up to 9mm long and stays on the plant surface for a brief 80 minutes. If it travels into the stem, it can kill the whole plant.