Rose growers often use a combination of Amblyseius swirskii and Amblyseius cucumeris to fight the most common pests in their crops: thrips and whitefly. However, these two predatory mites have difficulties in settling themselves on the plants, they die soon after introduction. So these beneficials need to be released repeatedly (every two to four weeks) – a costly and time-consuming effort.
But not every beneficial gives up so quickly. The predatory mite Euseius gallicus is an exception: it is the only one that settles permanently in roses. Moreover, this beneficial is polyphagous – it eats both thrips and whitefly – so gallicus is an excellent guardian in rose cultivation. And last but not least: the predatory mite is not afraid of cold weather. It can thrive from temperatures above 10°C and thus can be used both early and late in the season.
Biobest sells gallicus under the commercial name Dyna-Mite G-System. One package – a cardboard bottle – contains 10,000 predatory mites that can be spread over the plants thanks to a sprinkler lid.
So what’s the difference in strategy using gallicus instead of swirskii and cucumeris? “Introductions of gallicus should ideally start in the beginning of the season, somewhere between week 2 and 4,” says Yann Jacques, product manager macrobials at Biobest. “We recommend two releases at a dose of 50 mites/m² each.”
Another advantage of gallicus is that it is very responsive to Nutrimite, Biobest’s pollen-based food supplement. “In fact, the mite population tends to explode after Nutrimite is applied,” says Yann. “Thanks to this, gallicus populations are able to sustain themselves, so that they are at fighting strength when summer begins – when thrips and whitefly usually break through.”
According to Yann, rose growers should apply Nutrimite every two weeks after they’ve introduced the Dyna-Mite G-System. The recommended dose is 500 grams/ha. When summer has arrived and the first thrips have been detected, artificial feeding can be stopped in order to keep the mites’ full appetite for pest insects.
When summer is over, at the end of the season, a reintroduction of Dyna-Mite G-System is recommended, in order to prevent a late attack of thrips and whitefly. Applications of Nutrimite should also be resumed to ensure that the gallicus population remains in place until the end of the season.