I've soaked chewing tobacco, diluted the liquid till it looks like
weak tea, added baby shampoo and sprayed. Don't know if its the
constant rain OR my concoction but my lillies have not been stripped
this year. Will try spinosad but where can I find it?
In My Garden Blog
New England
July 2, 2009
By
Suzanne DeJohn,
Cambridge, VT
Left unchecked, lily leaf beetles can decimate lily foliage.
Lily Leaf Beetle
If you grow lilies, you're probably familiar with the scarlet lily leaf beetle (Lilioceris lilii). And if you don't know this pest, be on the lookout. Both the larvae and adult beetles eat lily foliage; a bad infestation may reduce plants to naked stems.
A European native, lily leaf beetle was discovered in Montreal in 1945 and seemed confined there for decades until it found its way to Massachusetts in 1992. Since then, it has spread rapidly and is now a major pest across the Northeast.
Lily Beetle Life Cycle
The adult beetles are about a half-inch long and bright red, with black legs and antennae. They emerge from hibernation around the time lilies sprout, and the adults begin feeding and laying eggs on the undersides of leaves. The eggs hatch in four to seven days and the voracious larvae begin eating.
After two to three weeks the larvae drop to the ground to pupate. A few weeks later, they emerge as adults and again begin feeding on lily foliage, continuing to do so through the rest of the growing season. The adults overwinter in soil or plant debris.
Control
While the adult beetles are easy to spot and hand pick, the larvae are more of a challenge. Not only are they harder to see, they have the particularly offensive habit of piling their own excrement on their backs as they feed, rendering them slimy and difficult to squish. This protective covering also makes them challenging to control with sprays.
Some gardeners report limited success using neem oil. However, a relatively new pest control product called spinosad appears promising in controlling not only the lily beetle, but other garden pests as well. Spinosad is made from the fermentation of a naturally occurring soil bacteria. This organic biological pesticide is also effective at controlling caterpillars, leaf miners, thrips, and fire ants. It's sold under various trade names; read pesticide labels, looking for spinosad as the active ingredient. Spinosad attacks the nervous system of the pests, causing them to eventually become paralyzed and die.
Lily leaf beetle lays its eggs only on true lilies (that is, in the genus Lilium) and fritillaria. True lilies include Asiatic and Oriental lilies, as well as tiger lilies, turk's cap lilies, and Easter lilies. However, the beetle has been observed feeding on other plants, including hollyhock and hosta. It is not a pest of other "lilies" such as daylilies, calla lilies, and water lilies, none of which are true lilies.
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Comments on Lily Leaf Beetle
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We welcome your questions and comments about this column. If you have gardening questions unrelated to the column, please ask them on our message boards.
Margaret
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Bill D.
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It must be your concoction -- my plants are stripped about 3/4 the
way up. Fortunately, it hasn't prevented them from blooming. K-Neem
definitely works; however, it needs to be sprayed often to maintain
control. I would be interested in the organic option if it's
systemic...
Denis Wang
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I've had great success this year using diluted Dawn detergent (2
tbsp per gallon). It killed the adults and dried up the eggs - not
a larva among all the lillies.
Linda
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Hi Dennis. Did you spray the entire lily? Do you have to repeat the
application? My poor tiger lillies :(
Donna B.
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I have had trouble with these beetles on all my lilies, including
the day lillies. I have used safer insecticidual soap and it worked.
My only problem is that you have to reapply after it rains &
Connecticut had 25 straight days of rain. I haven't noticed them in
about 3 weeks, so I guess it worked. I never had them until the
grubs returned to my lawn, I need to put down more milky spore & I
will try it in my flower beds this time & see what happens.
Suzanne
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Spinosad is sold under the trade name Monterey Garden Insect Spray
and Green Light Lawn & Garden Spray with Spinosad, among others.
When you spray it be sure to cover the undersides of the leaves,
too. That may help it last longer since the rain is less likely to
wash it all off. As far as using tobacco, people used to use
nicotine sulfate, extracted from tobacco, as an organic insecticide.
It's rarely used now because it's considered so toxic and is readily
absorbed through the skin.
lena c
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unfortunately though it is organic, neem does not differentiate
between insect species, most pesticides do not, and whomever gets
sprayed suffers the effects. i find that persistant plucking of the
adults, as well as squishing the bright orange eggs radically
reduces the larvae population to a managable proportion. the adults
can be difficult to catch, so using a container of soapy water, or
with poison, to catch them as they drop, can be easier. the larvae
are pretty gross, and when plentiful enough, i simply cut off the
infested leaves into the same container. usually i try to plant
lillies also, behind another plant that will hide its defoliated
bottoms!
Suzanne
Thanks for the tips, Lena. The beetle has become such a problem that
people are giving up on lilies altogether -- which is too bad
because they're so beautiful. Good luck with yours!