"Robert (Plymouth)" writes
wrote:
: Hi,
:
: I have a 4m high by 9m long conifer hedge. It is either a leylandi or
: thuja type, although I have done some research I cannot be exactly
: sure.
:
: The hedge is made up of 4 trees, and since its last pruning about 6
: months ago (which I did not do), some brown patches have appeared,
: majority on 1 tree, slightly on another and none on the other 2.
: I have researched the potential cause of the browning, and know it
: could be due to many causes, and that it may never recover. One of
: these could be some kind of insect infestation.

What kind of insect infestation? It affects what treatment is
appropriate.
:
: In the scenario of an assumed insect infestation I was thinking of
: getting some insectiside and spraying the hedge. I am under the
: opinion of spraying it for the sake of it will at least eliminate an
: insect cause, even if not actually present.

Not necessarily. Insect pests are becoming increasingly resistant to
available pesticides.
:
: I haven't got a clue what type of insectiside to use or what
: equipment. Also the potential side effects on the hedge itself,
: flowers and other plants in the same soil, animals and children.

Sounds like bad pruning has led to die back to me. I wouldn't spray at all,
certainly not just on the off chance as the whole food chain can be
interrupted let alone any beneficial insects getting zapped

I'd agree. Assuming you manage to avoid spray drift and keep animals and
children away, the killing of beneficial insects may mean you have more
problem from other insect pests on other plants (plant eating insects
are adapted to breed quickly once a food source is found; predators
obviously are slower to react since there is no point in their
populations building up until the prey population has established
itself). In addition, some insecticides have adverse effect on
particular types of plant.

Reading the list of precautions on any insecticide bottle suggests that
these are serious chemicals, and the thought of spraying 'for the sake
of it' even if there are no pests present rather alarms me. Remember too
that many pests will have been killed off by the cold winter, and in
this case spraying is a waste of money.


--
Kay