The first greenhouse behind the buffer tank that is the direction to get to one of the sites of the tomato growing company Greenway on the Kreekrug. It can't be missed either, a big white buffer tank with Greenway on it. Much easier to miss are small pests in the greenhouse. Growers are keen to get rid of them. Eric Volkering, Greenway I's site manager, therefore deploys pheromones to detect Tuta absoluta and Nesidiocoris tenius and monitor population trends.
Eric Volkering flanked by Eric Kerklaan and Lennart Simonse of HortiPro
Greenway's site on the Kreekrug consists of two areas of just under three hectares, making almost six hectares of greenhouse. This season, for the first time, the greenhouse is full of two ToBRFV-resistant cocktail tomato varieties from Rijk Zwaan's range. These are Lucioso and Amelioso.
In addition, in the greenhouse, for those with an eye for it, the pheromone traps stand out. Or the signs on the various gutters indicating where the pheromones can be found. At the top of the greenhouse, for signaling and monitoring Nesi, and at the bottom of the greenhouse, for signaling and monitoring Tuta. Those pheromones are from HortiPro, who are visiting Eric on the second Wednesday of June with Eric Kerklaan and Lennart Simonse. The latter has just walked out of the greenhouse with a sticky trap containing, fortunately, mostly waterflies and no Tuta.
Three rounds
The pheromones, deployed from the start of cultivation and even before the plants were in the greenhouse, have done their job. Grower Eric and Lennart note this with satisfaction as they discuss a chart with figures. Figures showing how many males and how many females of Tuta have been found at the various census sites. And Isonet T has also been weighed, indicates Lennart. That way, the grower and HortiPro keep track of how much pheromone is left before another series of Isonet T is hung.
There are two weighing points in the greenhouse. This makes it easy to keep track of the release of the pheromone. Isonet T usually lasts three to four months. In summer, there is always the risk of slightly faster evaporation. A weekly round to check prevents problems. Eric from HortiPro knows of examples of growers using Isonet T, also a pheromone, but a confusing pheromone from the labs of ShinEtsu, for which HortiPro handles distribution in the Netherlands.
Growers deploy this confusion pheromone to prevent tomato leafminer mating. "Nowadays, we see growers have gone from using Isonet T twice to three times a year," says HortiPro. With this, growers are actually deploying Isonet T year-round. Greenway is one such grower. Grower Eric is adamant: "Three rounds of Isonet T is how it should be done."
Monitoring population structure
At Greenway, this season's regular tomato crop followed an autumn crop. In is, a small infestation with Tuta was already present. In the current crop too, tomato growers on the Kreekrug suffered from it. In early June, the time comes when the greenhouse is Tuta-free. In week 23, only one female is counted. Grower Eric is delighted. "If the greenhouse is free of Tuta, maybe we can start using biological agents after all," he says. That wasn't possible before because the grower also had to spray to control Tuta. A disadvantage of this is that it also targets the predatory bug Macrolophus, whereas growers also use this predatory bug as a biological control agent. Greenway's other greenhouse at this location is already Tuta-free. Macrolophus has also been released there.
PheroTuta has also been on the market since last year. Greenway was one of the first users. "With this pheromone, you keep an eye on the population build-up and can anticipate in time," says grower Eric. The purpose of this pheromone is to warn growers, Lennart stresses. The idea for developing the pheromone came up when strict requirements were imposed on growers regarding Tuta for tomato exports to Japan. The moth was not allowed to be present. A phytosanitary requirement from the Japanese, HortiPro's Eric knows. Like grower Eric, he remembers well the first deployment in the greenhouse on the Kreekrug. "Back then, the trap was quickly full," he says. Now that is no longer the case. In week 23, there is hardly any Tuta left.
Tuta absoluta is still a relatively new pest in tomato cultivation. Growers have been dealing with it for more than five but less than 10 years. Control is difficult. The remedies that are available also control Macrolophus, as mentioned above. The bug itself is native to tropical regions. In the Netherlands, however, the pest insect has also increasingly established itself. As a result, growers are fearful of the critter 'blowing into' their greenhouses. "At tropical temperatures, Tuta then multiplies at lightning speed," warns pheromone specialist Eric.
So it is best to monitor with pheromones, but if Tuta does strike, it can be seen as larvae burrowing into the tomato leaves or holes under the crown, grower Eric knows. The latter is especially common when growing coarse vine tomatoes. On holiday in Scotland this year, he also saw Tuta damage on tomatoes in a restaurant. "Nobody cared, but I left that tomato anyway," he laughs. Such Tuta damage is a thing of the past for him, as are 'clouds' of moths. "Ending the year without Tuta, that would be nice," he says.
For more information:
Eric Kerklaan and Lennart Simonse 
HortiPro
[email protected]
www.hortipro.net