Hemlock Woolly Adelgids in Your Trees?







Do your hemlock trees look like they’ve been decorated for Christmas?  Those white spots indicate that your tree is infested with woolly adelgids.  Left untreated your hemlocks will die in 3 to 5 years.


You can call in a professional who will suggest spraying twice a year – once in April and once in September.  The charge for one application is $165.  Or, you can select the bargain seasonal rate of $325.


Or, you can do it yourself.  Here’s the simple solution I came up with after reading scads of articles on Internet and chatting with a half dozen gardening experts.


=== What to do

Spray trees with a 2% solution of horticultural oil.  This is a contact remedy, not a preventative.  Therefore, apply only when insects are present, i.e. look for white wooly spots before spraying.  The white spots may still be on the foliage following the treatments, but they will disappear over the next few months with new growth.


Wear eye-protecting goggles for sure.  Optionally use rubberized gloves and a facemask.

Do not spray on a windy day.

Reapplication may be necessary if rain occurs within 24 hours of application.


=== What to buy

$9.00 "All Seasons spray oil" – the concentrate contains 98% active ingredient

$7.00 Gilmore hose end sprayer (Home Depot – life time guarantee)


=== What NOT to do

Don’t apply petrochemical insecticides to an infested hemlock. THIS IS IMPORTANT. County Extension Services will recommend a variety of petrochemical insecticides, such as lindane or dursban, diazinon or fluvalinate, whereas horticultural soaps and oils are just as effective and safer to humans and the environment.


Don't buy the ready mix 2% solution that comes in a hose end spray bottle (cost $12.00).  The output from mixing with the hose water greatly reduces the effective resulting spray to appreciably less than 2% and it won’t provide coverage for more than one or two trees.