Friday, August 18, 2017

Bald Patches on the Leylandii Hedge? It could be Mites and Aphids







The spidery web of the Conifer Mite



As a neighbour there are hundreds of things we can do to irritate the people next door.  It could be as simple as having a dog bark late at night, blocking their driveway, argue over boundaries or have late night parties and treat their garden as a bottle depository.

One of the main reasons for falling out in estates or houses with small gardens is planting leylandii hedging on boundaries or so close to the neighbours house you eventually block out all of their light in the kitchen and sap the nutrients and moisture from their garden. 

Planting leylandii as a boundary has been a popular method of irritation since the 1970’s and since leylandii can grow up to three feet in one growing season it’s only a handful of years before you have your day in court with the neighbours or at least being aware of their disapproving looks through the ever growing boundary hedge as you take the shopping into the front door.

There is help at hand though for anyone who have these massive out of control boundaries. They are tiny and can be extremely destructive.  The conifer mite and cypress aphids have taken full advantage of the growing number of hedges and have spread unhindered since the 1980’s.

Up until recently you would have thought that the brown patches on the hedges were down to over zealous cutting back – Once you cut off the green growth of leylandii the green doesn’t grow back. This type of over trimming will account for a number of brown patches but it’s these small insects that are causing the main bulk of the problem. Most of them are so small the only tell-tale sighs are the small spider web looking fibres on the brown leaves. There are over 500 species of sap sucking aphids and a couple of them are having their moment in the limelight.

The two most attracted to leylandii are the conifer mite and cypress aphid.

Conifer Mites Oligonychus ununguis -
These spider mites also love spruce, fir, juniper, pine, hemlock and others. The infested trees display mottled foliage which may appear brownish-grey, and needle loss may occur. 

To confirm a mite infection, lightly tap the damaged branches over a white paper and examining the paper for reddish-brown mites which are about the size of pepper grains. In heavy infestations like in the image, spider webbing may also be conspicuous. The actual mites are so small they can harly be seen

2. Cypress aphids -Cinara cupressivora
Damage caused by cypress or conifer aphid develops in late spring and summer. It is found most often at the base of the hedge, but can develop at any height. Large greyish greenfly are sometimes found, but the hedge browning often develops long after the aphids have left the foliage. Clues are left behind, including cast aphid skins and a black fungal growth (sooty mould) that grows on the sugary honeydew excreted by the pest.

There are ways to minimize the infestations and plant damage but generally the damage has been done by the time you see the brown patches and the insects have moved on to pastures new. Chemical spraying would be extremely costly, difficult to cover the entire area and pretty dangerous on a large hedge. Some people put a hosepipe into the tee and flush out the insects as they don’t like too much moisture. 

Maybe the best way to control the spread of mites and aphids would be to start taking the hedges out and replacing them with alternatives. In Inishowen the best hedging we have is escallonia although this wouldn’t suit colder inland areas and it also has a few problems of its own namely fungal leaf spot. 

There’s also the lovely slow growing box hedge which will give a fine boundary but wouldn’t be too invasive or antisocial. These again have a problem called the Box Tree Moth. It’s the caterpillars that do the damage and they are spreading quickly with no predators at present. They were first noticed in 2007 and since 2014 they have become more established with sightings throughout the country.
It seems there are no complete solutions to neighbours boundaries, even fencing needs looking after every year. For some the best solution for happy neighbour relations is to avoid erecting boundaries all together and have an open dialogue with the people across the way, not blocking them out, just giving them the nod when you see them. 

I’m all for that, as long as they don’t keep popping in for cups of tea .

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