As happens every year, spider mite has appeared early in sweet pepper crops. While the infection pressure and pest distribution will differ per greenhouse, the one certainty is that Phytoseiulus persimilis can deal with sudden population increases. This predatory mite can rid a crop of spider mite hot spots within a few days.
Red spider mite – the bean spider mite, Tetranychus urticae – is one of the most common pests. Keeping it under control is an annual challenge, says Biobest crop advisor Bart Elseviers. “However, by scouting carefully and introducing predatory mites in time, growers can keep spider mite well controlled,” he says.
Bart recommends starting the control programme at the beginning of the crop, with introductions of Amblyseius degenerans (Degenerans-System) and sachets of Amblyseius cucumeris (ABS-System).
“Our ABS-System ensures a continuous release of predatory mites over several weeks,” he says. “This ensures growers achieve a healthy population ready to take immediate action when the first spider mite appears, the so-called ‘standing army’.”
Biobest is the only company producing Amblyseius degenerans – which according to Bart works particularly well in combination with Amblyseius cucumeris.
“Other combinations also work well, such as Swirskii-System and Montdorensis-System – the choice often depends on which pests are present,” he explains. “For example, if you have whitefly issues, Swirskii-System is the better option.
“Biological pest control programmes should be customised to the situation in individual crops. Anyone needing advice, including regarding the best dose rate, should contact their Biobest advisor.”
While the preventative predatory mites play a useful role slowing down red spider mite infestations, Bart warns the pest pressure can still increase later in the crop.
“Phytoseiulus-System then plays its key role,” he says. “This highly specific and mobile predatory mite has an enormous appetite enabling its population to increase faster than the spider mite. Phytoseiulus-System should be applied curatively at a rate of 20 to 25 units per m² – depending on pest pressure.”
“This beneficial mite should be sprinkled near the spider mite hotspots where it will immediately get to work. If necessary, the treatment can be repeated several times.”
“Phytoseiulus-System develops best at low humidity and high temperatures, above 30°C – so warm and dry conditions,” continues Bart. “If greenhouse conditions have been cool and humid for a while, this pest can get the upper hand again. It is therefore wise to scout well after such a period and possibly reintroduce Phytoseiulus-System.”