Hans Sikkema coordinates the plant protection program for Dutch greenhouse grower Red Harvest on their 30 hectares of tomato cultivation in Middenmeer. This year mildew is a challenge for them. "We’re trying to use biological solutions as long as possible. Only Rocket is my first choice for curative chemical treatment.”
Red Harvest’s company in Wieringermeer contains four sections of 7.5 hectares each. There are several varieties of large TOVs as well as cocktail tomatoes, half of which are grown under lights. The plant protection team is always alert, because of the differences in planting times, growing conditions and disease susceptibility.
Sikkema: "Alertness is key, especially when you see a rise in pest pressure. This happened with mildew a couple of times."
Consultant Jan-Paul de Wit from Royal Brinkman adds: "We’ve had Mildew under control since mid-September. Other growers who planted early for lit cultivation are seeing their mildew pressure rise again. It’s been going up and down this year."
Chemical mildew treatment
Natural predators and organic plant protection products are the base ingredients for the crop protection plan at Red Harvest. Shortly after planting, Macrolophus and parasite wasps are deployed against whitefly, the main pest in this crop. Mldew control starts as soon as the first leafs are showing spots.
Sikkema: "We started with two organic plant protection products in June and followed up with treatment with Rocket, my first choice for curative chemical treatment." There are many treatments available for mildew control, but the team leader says that Rocket offers several advantages. "The most important is its quick and effective action, the short waiting period of one day and its suitability for integrated cultivation. It doesn’t affect Macrolophus and wasps."
Technology consultant Irma Lukassen from Certis says that a substantial mildew contamination is impossible to fight with just only organic / biological plant protection. "Those mainly work preventively, like most allowed chemicals. Curative treatment will be required at some point, preferably several times in succession."
Sikkema and consultants say that four curative sprayings are a minimum requirement to free the plant from mildew entirely. De Wit: "The label prescribes switching to another agent after three sprayings with Rocket. Later you can do two more, if necessary, since in Holland, five sprayings are allowed per year."
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