After thrips and aphids grew to become an extremely serious problem in 2015, rose grower Van den Berg Roses decided to combat the pests with chemical crop protection agents. While it was a pity that things went the way they did, this cloud had a silver lining, as it provided a clean start for cultivation in 2016. At the end of July, it appeared that the beneficials Aphiscout and Aphilin by Koppert had successfully kept the crops aphid-free. "It's an outstanding result," say division managers Pieter van der Eijk and Dawid Gorzolnik.

Van den Berg Roses is a big name in international rose production. The company has three locations in the Netherlands, as well as one in Kenya and one in China. Its good reputation is partly thanks to the quality of the roses. Biological crop protection is important for the company's quality assurance policy, as successful biological methods eliminate the need to use chemical agents.

A clean start
That said, it hasn't always been a success story. In 2015, for instance, the company resorted to chemical crop protection agents to combat thrips, aphids, and scale insects. Nevertheless, this meant that Van den Berg Roses could enjoy a clean start in 2016. Acting as division managers, Pieter van der Eijk is responsible for a division measuring 2.6 hectares and Dawid Gorzolnik for a division measuring five hectares. "We no longer had high expectations of the chemical crop protection agents," says Pieter van der Eijk. "The agents quickly lose their effectiveness. In previous years, we've had to spray the entire crop every four or five weeks. That's not what you want as a grower, partly because growth comes to a standstill after a chemical application and partly because you suffer production losses."

Building up populations as a preventative measure
With this in mind, the growers consulted with Koppert consultant Muriel Klein Beekman and decided to implement a preventative measure to combat aphids, involving the use of banker plants to hang up populations of the parasitic wasp Aphelinus abdominalis (Aphilin) as early as the winter. Around the time that the banker plants had been eaten up, van der Eijk and Gorzolnik switched to the gall midge Aphidoletes aphidimyza (Aphidend) and Aphiscout. Aphiscout is a new product based on a mix of five different natural enemies of aphids. The two products were released in relatively large numbers.

Problems are a thing of the past
As van der Eijk and Gorzolnik explain, this approach produced spectacular results at the end of July. Dawid Gorzolnik recounts, "I would normally spray my division with Plenum every few weeks to combat aphids. Nowadays, I only have to treat a couple of square metres once every four or five weeks, so we're talking about very isolated spots." Pieter van der Eijk adds, "Now, in July, we would usually experience lots of problems with aphids, but the picture is very different. Even though we still notice them, problems with aphids are a thing of the past. Even in cultivars that are vulnerable to aphid infestations, such as Avalanche Peach, Avalanche Pearl, and Avalanche White, the results were and still are very good."

"It's an outstanding result," as David Gorzolnik puts it. While Van den Berg Roses has so far not used any chemical crop protection agents in 2016 except to combat mildew, it needs to be wary of scale insects. All other aphid species as well as thrips and whitefly are neatly under control thanks to Koppert's beneficials.

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Koppert Biological Systems