Biobest R&D targets new crops for Nutrimite™

22/02/2019 - The strategy of cultivating predatory mites in glasshouse crops on an artificial diet, in the absence of the pest, is not new.

Currently many growers introduce predators weekly, or once every two weeks. This is because the predators generally have trouble establishing on the crop due to a lack of (suitable) food or affinity with the plants. Unfortunately, prey mites used for predatory mite rearing are unable to colonise ornamental crops. Even if predatory mites are introduced every two weeks, they generally remain scarce.

To help resolve this issue, Biobest launched Nutrimite™ (Typha pollen) in 2013. This high-quality pollen provides an excellent food source for the predatory mites. Applying Nutrimite™ once every two weeks using a blower helps to stimulate predatory mite population growth − the results can be spectacular. A minimal, barely visible layer of 500g of Nutrimite™ per hectare, applied once every two weeks (or 250g once a week), is sufficient to help the predators colonise the plants.

The effect of Nutrimite™ on the establishment of different predators varies greatly, with the best results achieved with Degenerans-System (Iphiseius degenerans), Swirskii-System (Amblyseius swirskii) and Amblydromalus limonicus.

Biobest regularly carries out trials with Nutrimite™ and a range of natural enemies in a variety of different crops. Ultimately, the predatory mites establish successfully before the prey is present. As a result, this innovative strategy is being increasingly adopted in a range of commercial crops. In collaboration with growers, new crops are being tested to develop specific introduction schedules. Successful introduction programmes now exist for cucumber, Gerbera, rose and sweet pepper crops.

In the case of Gerbera, a single dose of 50 A. swirskii per m² was introduced preventatively mid-February. Predatory mite establishment was compared for three different introduction strategies: without supplementation, with the addition of prey mites at 2000 prey mites/m² every two weeks and, lastly, with the addition of Nutrimite™ (500 g/ha/2 weeks). After four weeks, A. swirskii reached significantly higher density levels with Nutrimite™. When the same three strategies were tested later in the season, in the presence of red spider mites and whitefly, no clear-cut differences in predator density levels were observed. Therefore, we advise using Nutrimite™ preventively, with the first predatory mites introductions, to help boost population establishment and growth to a high level.

In 2018, further tests were carried out in potted plants. In a glasshouse containing Calathea rufibarba cv. Wavestar (Fenzi), 50 Amblyseius swirskii predatory mites were released per m² in a single dose, at 21°C and a relative humidity of 60 to 90%. Nutrimite™ was applied with a blower every two weeks. The schedule proved sufficient to enable the predatory mites to colonise the plants. Senior Biobest Researcher Juliette Pijnakker was impressed with the results; “After 43 days we recorded a density of 17 predatory mites per plant,” she says. “Normally, without pollen, no predatory mites would be found at this point, unless we kept reintroducing them onto the crop.”