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Lily Beetle
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Yikes!
Not an easy garden pest to control if you grow Oriental Lilies.
Here's your battle plan!
By Evelyn Wolf, Garden Possibilities!
This devastating garden pest attacks, and lays
its eggs on, Lillium species mainly – the stunning bulb Lily family of plants.
Lily Beetle was first discovered in North
America in 1992, most likely hitch-hiking in a shipment of Lily bulbs from
Europe. It has since spread throughout the northeast to the complete demise of
gorgeous Lily beds everywhere. For years collectors tried product after product
for control, but the Lily Beetle’s tenacity was no match.
Unlike most other garden pests, Lily Beetle
(Liloceris
lilii),
has no natural predator on this continent,
which is how they’ve been so successful in their aggressive march through Lily
beds here, unlike in their home European territory. They are strong fliers so
can seek out their target, but their eggs are also moved around on host plants -
i.e. your
new Lily bulb purchase!
Identification:
Adult Beetles are easy to spot - bright
orangey-red, square-ish, and about 1/2" long. Their larvae are mushy slug-like
things with swollen bodies and black heads that look just like a little slimy
mass of fresh bird droppings. The fecal matter analogy isn't so off-base
either! Larvae cover themselves with their own fecal matter to deter
predators. (That’ll work!)
Life Cycle:
Adults
over-winter in the soil’s surface, emerge in spring (in sync with the emerging
lily foliage),
and immediately mate. (Early to mid May you'll find adults tucked into the
leaf joints - often in pairs busy mating.). Soon after mating, females lay brownish-orange eggs on
the undersides of foliage that hatch within 4-8 days. (Mid to late May,
routinely check the undersides of leaves for an orange line of clustered tiny
eggs). This more or less brings
us to early June here in the northeast, when you'll see the young larvae
initially feeding on the undersides of the foliage, but later on the upper
surfaces, stems, and buds. If you where vigilant about getting the adults and
crushing the eggs, you shouldn't end up with too many larvae.
This larval feeding phase of their life cycle
is the most destructive as they voraciously munch holes in leaves to the point
of leaving nothing behind, and lasts for 16-24 days. The happily fattened
larvae then drop to the soil to pupate. New adults emerge 16-22 days later
(which brings us to more or less early August) and the new adults feed on your
Lilies for the rest of the season. These are the ones that will tuck into the
soil over winter and begin the cycle again in spring.
Each female beetle produces 250-450 eggs.
That’s a lot of lily beetles! Left unchecked they’ll overrun and demolish any
host plants in the vicinity within just a year.
Management:
If you focus on
the Lily Beetle’s life cycle, it's easy to see when you can be effective in
controlling this devastating pest. Cultivate the soil surface in late fall
searching for new adults bedding down for winter. In early spring, just as lily
foliage is emerging, the beetles will too. Be vigilant for a couple of weeks
and hunt down the emerging adults that can be found hiding in nooks all over the
plant, before they have a chance to mate. (Trickier than it sounds since they
have the uncanny ability to sense your thoughts and drop to the ground just a
fraction of a second before your thumb and forefinger closes around them!). A
week or so later start another search and destroy mission each day, this time
looking for eggs and newly hatched larvae. In early August watch for new
adults.
Avoiding the
Problem: If you’ve grown Lilies successfully in the past without meeting
this nasty pest, don't be too smug! With just one new un-inspected purchase the
situation can change quickly. When purchasing new lily bulbs, or accepting a
gift from a gardening neighbour, rinse them thoroughly before they even get near
your garden, and make sure the rinse water goes down a drain. Remember, you're
looking for bright red adults or slug-like larvae in the soil - not eggs, so
they should easily rinse away if present. Inspect them thoroughly!
In the case of potted bulbs already growing,
rinse them nevertheless. The growing plants will be weakened, by they won’t
die. Wash away all soil that’s in among the roots using room temperature water,
and also inspect stems and foliage for eggs. Even just one beetle that makes it
into your garden can begin the ravaging cycle so don’t let your eagerness to get
your new plants in the ground deter you from a thorough de-bugging.
Even with vigilance, once you've got Lily
Beetle you've likely got them for good. Control is the best you can hope for.
Focus on its life cycle so you know what to watch for, when. With a watchful
eye, a battle plan calendar, and a gloved hand, you'll be able to keep their
population down to a manageable level and continue enjoying your beautiful
Oriental Lilies.
Evelyn Wolf, Garden Possibilities!
evwolf@rogers.com
In my new home, I am surrounded by Black Walnut
trees so I'm busy collecting
information on the
allelopathic
toxin called Juglone and which plants
are most susceptible to it. If
anyone has any experience
with this frustrating problem, please share! Much of the
information I've collected so far traces back to only a few
original sources so any first hand information would be
welcomed before I kill too many plants!
Evelyn
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