The mite can cause significant downgrading of fruit and appears to have been unaffected by the cold early winter.
Kent-based UAP fruit agronomist Neil Obbard said he had been finding it in an increasing number of orchards since he first noticed it in 2009 - five years after it became prevalent in the West Midlands and East Anglia.
Obbard maintained: "If the pest is ignored it multiplies to a high enough level to cause considerable damage to the fruit due to the feeding of adults and larvae around the calyx. This causes rusetting, rendering the fruit unsaleable."
He added that egg-carrying female mites overwinter on the tree bark and in the spring migrate to the rosette leaves and blossom trusses and later the fruitlets to feed and lay their eggs.
East Malling Research team leader Professor Jerry Cross said the mite was present in many orchards "without growers realising".
If left alone, over a few years it can increase to damaging levels and so it cannot be ignored, he warned.
RECOMMENDED TREATMENT ENVIDOR SPRAY NEEDS ONLY ONE DOSE
Fruit agronomist Neil Obbard has found the most effective answer for flat scarlet mite to be an Envidor (spirodiclofen) spray in late May or early June. "It does a super job and you only need one dose," he said.
Envidor has the added advantage of controlling other pests that can be present at the same time, said Obbard. These include red spider mite, rust mite, mussel scale and pear sucker.
It binds to the leaf wax to ensure the good rainfastness that is so important for their effective, prolonged control. Furthermore, it is safe to pest predators such as "typhs", Obbard added.