Bill,
Depends on when they are spraying. If in the evening, after the bees are
in the hive, you will probably experience little loss. If the bees are
directly sprayed in the field, then they will be killed.
Malathion is a fairly benign spray compared to most. But it is highly
toxic to bees when directly sprayed on them.  It is not a powder, so the
bees will not carry it back to the hive but will usually die in the
field. Powdered or micro-encapsulated insecticides are deadly to bees
because they are carried back to the hive as *pollen* and kill the brood
as well as the bees, including the queen.
If the bees are in the hive when the fields are sprayed, they will be
fairly well protected. It is direct spraying of the bees outside the hive
that harms them. So if you know the spray schedule, pen them up for the
day by screening the entrance and exits. Give them ventilation so they do
not overheat, but keep the lid on to prevent spray from entering the
hive.
Malathion, even though it is highly toxic to bees can be fairly safe to
the same bees if applied correctly, which is evening or night spraying
and, for extra insurance, keep the bees penned up the next day.
It has also been reported here that it is a good idea to videotape the
sprayer with a date and time stamp in case you have claims against them
later because they did not spray when and where  they said.
Bill Truesdell
Bath, ME
 
BILL HUGHES JR wrote:
 
> Hi to list,
>
> Tennessee is going to spry from planes ULV Malthion on every acre of
> cotton in the southwestern part of the state.  I have no colonies
> directly in cotton fields but some are extremely close.  The
> distances vary from 50 yards with trees in between to one mile.