Jan van Marrewijk B.V. in Dinteloord (N-Br.) cultivates tomatoes on about 12.5 hectares. Of these, 5.5 ha is lighted and 7 ha is not lighted. All tomatoes are sold via producer organization Prominent. The company has 12 permanent employees and - depending on the season - 40 to 60 temporary workers.
Van Marrewijk Tomatoes in Dinteloord has gone through an unpleasant period. In the lighted cultivation - which covers 5.5 hectares, about 40 percent of the total greenhouse area - the company first had to deal with the Nesidiocoris tenuis, a harmful predatory bug that is related to Macrolophus pygmaeus. "The Nesidiocoris causes deformities and slowly but surely destroys the plants. We therefore had to do something to eliminate this predatory bug," as Van Staalduinen looks back. Around mid-November, a choice was made for spraying with Gazelle, which meant that the balance of biological pest control was seriously disrupted. In that period, whitefly hardly received any resistance, so that it was able to expand considerably. The parasitic wasps that were used six weeks after the Gazelle spraying to lessen the whitefly, could not manage sufficiently. And what also did not really help was that during the period of the growth of the parasitic wasps, a sulfur spraying had to be carried out against the tomato russet mite. "That way, in a sense, we rolled from one problem to another," according to the manager. Afterwards, when we also had an outbreak of the Tomato Chlorosis virus (TOC), the company decided to stop the lighted cultivation earlier.
Fixed place in the spray schedule
In order to conclude the period of harvesting (from week 16 to 23) as uncontaminated as possible and to prevent further spread of the virus - of which whitefly is a carrier - the new agent Sivanto Prime was applied immediately after the heads were taken out. Although the experiences are still very new, Van Staalduinen is enthusiastic about the results. "Especially against adult whitefly it works excellently and is a very valuable asset," according to him.
The use for this season was still primarily an emergency measure; for the coming season, he expects that Sivanto Prime will be given a permanent place in the spraying schedule, immediately after the use of Gazelle. "I would prefer to go for 100 percent biological control; this is something in which we succeed well in cultivation without lighting. But in the lighted cultivation we simply need a correction measure to control whitefly. We can therefore use a strong, selective agent such as Sivanto Prime very well,'' he concludes.
Source: Bayer Glastuinbouw Koerier