Apple growers must be on the lookout for the build up of Flat Scarlet Mite numbers on leaves and fruitlet stalks this season, advises HL Hutchinson Herefordshire-based fruit agronomist, Jonathan Blackman. A combination of the early season and a build up of populations in affected orchards over recent years pose an increased risk, he warns.
"We need to be vigilant for the summer generation mites on the move; they are certainly appearing early," he reports. Signs of yellowing on the leaf mid-rib are a good indication of mite activity on the underside, he says. If 10 or more mites are found on a fruitlet stalk, Mr Blackman advocates treatment will be required to prevent fruit quality loss and russeting skin damage.
However, he also highlights that whilst treatment has been focused on eating apple varieties - especially Cox and Worcester type - older cider orchards can also be badly affected by leaf damage from Flat Scarlet Mite feeding activity. "Maintaining healthy leaves is essential to drive apple yield and quality for cider. Mite activity is an increasing problem that growers need to be aware of and prepared to tackle."
Mr Blackman welcomes the additional option of Agrimec under the SOLA scheme to control Flat Scarlet Mite this season. While the SOLA only covers Flat Scarlet Mite, it is known from commercial experience in mainland Europe that Agrimec will also be active against Fruit Tree Red Spider Mite and Apple Rust Mite which are present at the same time, and yet retain the important mite predators that could help further prevent pest populations building up. "It is extremely positive that we are no longer dependant on a single active ingredient for this difficult pest," he added.
An Agrimec trial last season, conducted by East Malling Research, showed more 99% control of motile Flat Scarlet Mites five days after application - significantly greater than for the ’standard treatment’, spirodiclofen. By mid-June, mite numbers on fruitlets were still 69% lower from the single Agrimec spray. The control of the motile forms resulted in a significant reduction in egg numbers.
Numbers of Flat Scarlet Mite (Cenopalpus pulcher) have been increasing in apple orchards over recent years, with very damaging populations recorded in a number of orchards in Eastern, South Eastern and Western fruit growing areas of the UK. The Agrimec SOLA, obtained by the HDC, allows for up to two applications a year, at a rate of 0.75 l/ha. The time scale for application, from May to July, should cover most crops.
