Page 18 - index

Sprays are no longer available to home gardeners in Ontario, and most of Canada.
For Americans, Bayer has a number of formulations containing “Imidacloprid” as an
active ingredient. Available at most hardware and gardening centres. The lawn and grub
granules will work, but awkward and expensive. Get the “Tree & Shrub” liquid and mix
it as per the weaker “insect “ spray. Spray
early in season for best effect.

The organic method is to hunt and
squeeze. Chew marks are often seen at the
place where the leaves separate from each
other. By opening the folds you can often
trace the chewing damage until you fnd the
borer. They can be removed and disposed
of. This can also involve squeezing the borer
between the leaves.

Leaf Spot:
This is an annoying and unsightly
condition involving small brown spots on
the leaves. This is a fungus that, though
unsightly, does little damage to the plant. A
spray of Benelate (or other fungicide) early
in the season can help with this, although
it is often necessary to repeat several times
in the season. Often the easiest way to deal
with it is to just remove the unsightly leaves and dispose of them (but not by putting
them in the compost). An increase of nitrogen in the fertilizer can often be helpful, but
too much nitrogen can make the plant more
susceptible to soft rot.

This is seen more often in older clumps
where there are a number of factors at work.
With the crowding, there is less air circulation
between leaves. There are fewer nutrients
available to each fan. Heavy rains can wash
out nitrogen. With the plant being less healthy,
the plant is more suspectable to diseases.

The fungus spores are in the soil. They are
more prevalent if infected leaves are left over
Winter. So a clean up of infected leaves in Fall
can help reduce the amount of fungus spores
present. If there are major problems, a mulch
around the base of plants can help. DON’T
place mulch at the base of the plant. Leave it
at least 3” away from rhizome.
16 Canadian Iris Society Newsletter