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Beware spider mite

Certis is warning ornamental growers of the onslaught of spider mites, which could be devastating to crops as weather conditions change

As the weather becomes warmer and drier, the threat of unwelcome pests increases. As a result, Certis is warning ornamental growers of the onslaught of spider mites, which could be devastating to crops.

Up until very recently, spider mite has been deterred by the persistent cold weather and low light levels, but Martin Donnelly, Account Manager at Certis, advises that vigilance and being prepared to act as soon as symptoms are identified is critical. 

“Spider mite thrives in warm, dry conditions and can cause complete crop ruin, feeding on plant cells leading to leaf spotting, yellowing, unsightly webbing and unmarketable plants. As we’ve had such a bad spring alongside last year’s earlier, warmer spring, the seasons have become quite unbalanced. The danger is that many growers might have forgotten about this pest, and presumed the season has come and gone.”

He explains that mites have been in diapause, hibernating over winter and waiting for the weather conditions to change before emerging. “Depending on temperatures, they have between a 7 to 35 day lifecycle, and given the right conditions, will rapidly multiply, causing an outbreak that can be disastrous to ornamental crops.” 

Martin warns that it is important to pay close attention to susceptible crops, such as ceanothus, hedera, choisya and pachysandra, monitoring all crops closely for the tell-tale signs. These include browning and/or mottling of leaves, with pests generally first seen on the underside of the leaf.  

Martin recommends employing Integrated Pest Management (IPM) techniques that combine chemical and biological controls.

“Applying Phytosure (Phytoseiulus), a predatory mite, should start when pests are seen,” he advises, noting that they need a food source to be sustained, so should not be used preventatively. “Monitoring is therefore a key priority.”

In pest hotspots, he advises either Spruzit (pyrethrin + rapeseed oil); a double active treatment that combines natural chemical and physical control of spider mite. But he warns that natural predators may be impacted. “Alternatively, to ensure there is  a minimal affect on Phytoseiulus, Majestik (maltodextrin) is ideal in delivering fast acting, physical pest control, and Phytosure can be introduced as soon as the product is dry,” Martin concludes.