Know your enemy because lawn problem may not be grubs but
lack of water
I've read conflicting advice as to just when to apply
grub killer (such as Diazinon granules) for this area.
Just what date, and how often, should this grub control
item be applied?
The best time is in late July or the first of August, so the
grub killer is there for the early stages of development of the various
lawn-damaging grub species. The younger the insect, the easier
it is to kill and the less damage it can do before your treatment
ends its feeding.
Diazinon has been widely used but Merit, more recently
developed, is currently in favor since it works at lower
concentrations. Mach2, which can't be purchased at a retail level
but pest control companies can apply for you, affects only beetle
grubs so it's a better choice for those trying to avoid unwanted
side effects such as reduced worm activity that can mean hardened
soil and weakened lawn roots. The active ingredient, such as
Merit (imidacloprid) or Diazinon, is listed on the grub
One well-timed application should suffice. If you're a
greenskeeper who knows precisely which beetle is doing the most
damage, you might alter the application time for what you know of
that species and its development in that year. If you're dealing
with an enormous problem and missed the July-August application,
you must probably treat the lawn in spring. However, your
choice of product is more limited then since Merit and Mach2 are
not effective on older, springtime, grubs.
An inch of water spreads grub killers best
Regardless of timing and type of killer, water it in so it
reaches the grubs. Keep a sprinkler running after your application
until a collection can or rain gauge placed there catches an inch
of water. If your soil is hard packed, apply the water slowly or in
several closely spaced episodes so it can soak in rather than run
off. An inch of water will push the grub killer down through 3 or 4
inches of soil, good placement for most grub activity.
Water. So many of us in this business wish those concerned about
their lawns would jump to the conclusion "water" before thinking
"grubs." We happen to be writing this on a summer day while also
tending sprinklers. We crossed paths with a fellow landscaper
and commiserated over how dry the soil is and how hard it's been to
keep things watered this summer.
We mentioned grubs as our writing topic of the day. "Grubs!"
said our friend. "I wonder about people who look at their lawns
every August and figure they have grubs. They might just need to
water better. Kick the sod, and if it rolls up like a carpet,
that's a grub problem. Otherwise, water's probably the answer."
Digressing to raccoons
We discussed a case we'd collaborated on, at a condominium
association where each morning the gardener had calls to come put
sod back in place. Raccoons were peeling the sod back to extract
grubs. The problem was not grubs, however. It was the hard packed
soil. The seven year old sod had yet to root into the soil
-- it was surviving on water and liquid fertilizer as if spread out
on pavement waiting to be purchased at the garden center. Core
aeration was the answer.
Back to grubs...
Grubs eat roots and that kills the lawn. The damage is at its
worst by late spring when grubs are oldest, before they emerge as
beetles. The grass dies or limps along on severely damaged roots
until the hot, dry weather comes, then gives up the ghost. If an
August-brown lawn still has enough root to anchor it against a
kick, you don't have enough grub activity to warrant grub
Studies show that a well watered lawn can sustain three or four
times as many grubs as one that's not irrigated, and is healthier
in many other ways. Greenskeepers respect these reports, so why
Water for lots of problems
It's dry! Brown lawns, mildewed Pulmonaria,
non-blooming Astilbe, scorched ferns, faded
Astrantia and flattened Anemone need water, not
pesticide. It takes a great deal of irrigation to make up for lack
of rain, so even if your sprinklers have been on regularly, your
plants may be parched. Poke your fingers an inch or two into the
soil, below the mulch or the lawn and see if it's warm there --
that means it's dry. Time to drag out the hoses.
The year of the bellflower
That's the title F.K. proposes for the year. "My peach leaf
bellflowers (Campanula persicifolia) have never stopped
blooming and are standing up tall. The clustered bellflowers
(C. glomerata) are blooming down their stems and preparing
to start all over again. The carpet bellflowers (C.
carpatica'Blue Clips' and 'White Clips') have bigger blossoms
than usual. Bellflowers are not exotic but they sure are neat!"
Black spot time!
Paul Emanuelsen, a zoo Adopt a Gardener who specializes in
roses, reports black spot beginning to show up now. One of his
floribunda roses is looking so bad he may just cut it down
and let it start over. Since it blooms just once a year in late
spring he won't lose any flower by doing this now but may net a
cleaner, neater look.
Overall rose health is as important in black spot control as
spraying. That means keep up with watering and fertilizer.
Emanuelsen's just applying his last Rose-Tone fertilizer for the
Green thumbs up
to putting a bucket under that leaky hose connection, if you
can't fix it yet. Use what you catch to hand water where sprays
Green thumbs down
to hose wrestling. How do hoses always manage to kink and
stiffen in ways that defy even the best hose reel and most agile
Originally published 8/2/03