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Pest pressure in strawberry is rapidly increasing

29/06/2021 - With the sun appearing regularly and temperatures rising, Biobest advisor Arno Hellemons warns against the arrival of pests in strawberry crops and urges growers to make sure they have a 'standing army' of biologicals ready.

“Strawberry growers with June-bearers and ever-bearers know that summer is associated with higher pest pressure,” says Arno. “Thrips is one of those insects that is always present, but at this time of year can increase explosively.”

“The three predatory mites – swirskii, cucumeris and californicus – are the most commonly used beneficials; released shortly after planting, they can quickly form an effective first line of defence."

Predatory mites against thrips

Arno recommends using different combinations, depending on the production system.

“In tunnel and greenhouse cultivations, average temperatures can quickly rise and the combination of swirskii and californicus works best,” he says. “For table-top growing systems and under rain shelters I recommend cucumeris and californicus."

“Growers can boost the predatory mite standing population using a feed supplement. Blowing Nutrimite™ into the crop, two weeks after releasing the predators, helps ensure sufficient beneficials are there, ready to quickly tackle an incipient infestation."

Feltiella-System is the ideal spider mite predator

Californicus is also an effective spider mite predator – especially in a preventative role. "To boost control during cultivation, many growers prefer Phytoseiulus-System,” says Arno. “This voracious predatory mite can clear a strawberry crop of spider mite hot spots in a few days.

“Sometimes the gall midge Feltiella-System is included in the strategy. Feltiella larvae are real spider mite predators and perform well in dark and cool conditions. However, growers need to be careful when using sulphur in the crop, as these predatory mites and gall midges do not tolerate it well. A good balance of both measures is important – we recommend sulphurising for no more than 4-5 hours every other night,” he says.

Control aphids biologically

Now Calypso is no longer permitted, strawberry growers are increasingly choosing to control aphids biologically.
Arno recommends a combination of Aphi-Mix-System (four species of parasitic wasps: Aphelinus abdominalis, Aphidius colemani, Aphidius ervi and Aphidius matricariae) plus the gall midge Aphidoletes-System.

“It is also possible to correct with Eupeodes-System during cultivation,” he says. “This hoverfly actively searches the crop for aphid colonies in which it lays its eggs. The same applies for the hoverfly Sphaerophoria-System – which is best introduced at temperatures of 20°C and above.”

PREFERAL® against whitefly

Finally, Arno highlights the damage caused by whitefly. "Whitefly eggs are partially controlled by swirskii while the pest pupae are parasitized by the parasitic wasp Encarsia-System.

“In addition, the biological insecticide PREFERAL® has a role to play. Containing spores of the naturally occurring fungus Isaria fumosorosea, it is highly effective against all whitefly stages: eggs, larvae, pupae and adults. In addition, it has secondary action against two spotted spider mite and thrips.

“For pest hot spots we have Protac SF®,” he says. “A special formulation of silicone polymers, Protac SF® forms a thin sticky net on the surface of pests. All adult whiteflies that are hit are immediately immobilised and quickly controlled. Protac SF® also has good activity against two spotted spider mite, aphids and thrips.”

Monitoring

As with all good biological control strategies, pest should be closely monitored using sticky traps and rolls to detect their presence.
“Growers can now enter this data into our Crop-Scanner App on their tablet or smartphone,” says Arno. "Easy to use, this App collects all the scouting data and enables a real-time visualisation of the greenhouse. It gives the growers an insight into individual pest pressures and population built up at any time. With this information you can adjust control strategies more efficiently.”

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