Can you imagine waking in the middle of the night fretting about Lily Leaf Beetles surviving the winter under the snow? Some would venture 'Get a life Phil!'
Rather than wrestling with sleep I headed to the computer at 3:00 a.m. My aim: to discover the least toxic methods of controlling our garden’s grossest pest: orangy-black larvae which, carrying a load of its own excrement on its back to ward off predators, can defoliate a lily in a matter of hours.
The internet has many good fact sheets on the Lily Leaf Beetle’s life cycle and most promote hand picking adult beetles and larva as the chemical-free way to control beetle populations. Lily leaf beetle will only lay eggs and develop on Lilium species (Turk's cap lilies, tiger lilies, Easter lilies, Asiatic, and Oriental lilies), and species of Fritillaria. The University of Rhode Island Horticultural Landscape Program has a good lily leaf beetle fact sheet. Click here to read it.
While the Lily Leaf Beetle (Lilioceris lilii) was first detected in North America near Montreal in the 1940’s – apparently imported in a shipment of plant material from overseas - we didn’t have these pests in our Kinburn gardens until 1996. Until then we rarely tended our proudly-grown pest-free lily varieties. Until then lily sales were also common at our nursery. Between the mid 1990's and 2005 we sold very few lilies because of the well-publicized ravages of the dreaded Lily Leaf Beetle. But sales of lilies are again creeping upwards as gardeners learn it is possible to fairly easily keep these beetle populations under control by using a natural plant by-product as a soil drench or hand-picking of adults.
Gardeners should be careful not to unknowingly introduce these beetles to uninfested gardens. Learn to recognize this devastating lily pest from the orange egg masses found on undersides of lily leaves, larvae and larvae with slimy black excrement on their backs and the orange-red adult. (For those reading this article on the internet, click on the underlined words for photos of the three life stages.)
If you prefer squishing forays!
Over the years we have been lucky to have nursery employees able to accept the beetle-squeezing assignment. Some of us wear latex gloves for this unpleasant chore, but a couple of years ago we had one employee who proffered orange-stained fingers as a show of his superior intestinal fortitude.
Our squishing forays begin in the spring as soon as lilies begin emerging from the soil. Adult lily beetles can then be seen both on the soil and on newly emerging lilies where egg-laying begins on the young leaf buds.
Devoted Lily Beetle squishers know that it is tough to catch adult beetles on mature lilies because, at the slightest plant jostle, the beetle falls to the ground. When approaching mature lilies, our first step to overcome this artful escape is to place under the plant a pail containing sudsy, detergent-charged water. We immediately lean the plant over the pail so that the escaping beetles fall into sudsy water. The escape-artists drown – the rest get squished. Any liquid dishwashing detergent (a teaspoon per 4 litres of water) can be used for this chore.
Listen for the squeek!
One statement in the Rhode Island fact sheet caught my attention. It reports that Lily Leaf Beetles squeak when squeezed gently. (It didn’t mention any sound made when squeezed vigorously!) When our daughter Shannon was younger, she delighted in catching Asparagus Beetles feasting on asparagus plants. She had adopted the role of Asparagus Beetle control agent in our gardens – motivated by being paid a nickel per dead beetle. One day she accidentally observed that Asparagus Beetles made sounds when captured and it became a game with her to cup one or more beetles in her hands and then put her hands to her ear to hear an ocean surf-like sound. Her young friends thought she was daft to hold beetles to her ear and few of them humoured her by trying her auditory experiment. As dutiful parents, we followed her youthful entomological investigation and we too heard the surf! We haven’t tried the experiment with the lily beetle, but being of the same family as Asparagus Beetles, I’ll venture the auditory effect would be repeated.
Background on Insecticidal Properties of Neem Tree Extracts.
My internet info quest took me to diverse web sites recommending botanically-derived products from Neem trees. Neem trees, in their native tropical regions, have for centuries been observed to have few insect pests and tropical peoples have been investigating and using the trees’ nuts, leaves and bark for pest control and other uses. Neem tree extracts have reportedly been utilized for ages in herbal medicine (even included in toothpaste formulations) and beauty product circles. My computer rambles revealed that Neem oil is promoted as a safe broad-spectrum insecticide in the hydroponics and marijuana growing networks. It's insecticidal properties (and especially its non-toxicity for those that smoke marijuana) make it useful for controlling ubiquitous nursery pests including spider mites, thrips, aphids, caterpillars and white-flies. However, traditional university and horticultural industry sources provided the information with which I am most comfortable!
A few years ago we bought some Neem Oil at a Detroit nursery (it wasn’t then available in Canada) to try as a Lily Leaf Beetle insecticide. We had heard American horticultural friends rave about its beetle-controlling powers. Unfortunately we now know that we had not been getting full benefit of Neem’s insecticidal abilities because we were targeting the wrong beetle phase due to that product’s incomplete instruction label. We had been spraying the adults as that seemed to be the interpretation of the instructions.
My internet surfing reveals that Neem products are ineffective on adult beetles. Adult beetles are simply repulsed by the oil’s unpleasant odour and move on to more appealing plants. Neem has to be contact larvae to achieve the desired beetle control action.
Lilies harbouring lily beetle larvae are easy to identify as long as you are looking for them –look on leaf undersides to see the tell-tale orange, egg masses or feeding larvae. When spraying Neem, make sure you thoroughly soak the underside of lily leaves to get the product directly on the larvae. Maintain the spray routine for three-weeks to wipe out progressive egg hatches. Most likely you’ll need to maintain your spraying throughout the season. Lily Leaf beetles are prolific breeders and may get re-established in your gardens if you inadvertently miss spraying some breeding areas.
Neem Oil Application Information
Neem may be purchased as liquid extract (e.g. Safer’s BioNeem) or "Whole Oil" products. Product labels should indicate the form you have either directly or indirectly. Extract forms are dissolve in water whereas ‘whole oil’ formulations (the type we sell) require an emulsifier, such as household dishwashing detergent (1ml/1litre), to be added to break up the oil into fine droplets. We’ve used both and mixed 30 ml Neem product to 1 litre of water.
Note: Many product labels indicate mixing 10 mls. of Neem Oil per 1 litre of water. But we've found this concentration needs to be tripled to be effective. Therefore our recommendation is to mix 30 mls. per liter of water.
The water used should be warm – between 50 to 95 degrees F. A knapsack sprayer is reportedly better than a hand sprayer for applying Neem. Keep in mind that Neem’s active ingredients, when mixed with water, lose insecticidal activity in about eight hours. It also loses its effectiveness when exposed to sunlight, so temporary storage of solutions in translucent containers should be in shaded locations.
The insecticidal ingredient obtained from the Neem tree is azadirachtin, a naturally occurring chemical that is structurally similar to insect hormones called ecdysones, Ecdysones control insect metamorphosis from larva to pupa to adult. Azadirachtin functions on larvae as an "ecdysone blocker" disrupting molting and thus breaking the beetle’s life cycle. When Neem is ingested by larvae, they stop feeding but death may take several days. Reapplication, at 7 to 10 day intervals, is required to keep up with the adult’s continuous egg-laying. Application is most effective when applied during humid conditions or when the plants and insects are damp. During hot conditions the spray frequency should be increased. Rain can wash Neem off the larvae so re-spraying may be necessary.
Early morning or late evening spraying minimizes inadvertantly spraying beneficial pollinators such as honey bees and ladybugs. Washington State University researchers have found that neem oil solutions are lethal to beneficial ladybug larvae and will sterilize or severely reduce the egg-laying capacity of adult ladybugs for as long as 10 days after application.
Neem oil’s active ingredient has some systemic activity according to a Montana State University report. It is taken up best by roots when applied as a soil drench but some foliar uptake occurs when applied as a foliar spray. Alkaline soils reduce the effectiveness of neem drenches.
Neem oil products are not an organic insecticide panacea. Make sure you target the problem insects and don’t spray your gardens broadly in the hope of getting the culprit!
For those less attuned to environmental impacts of toxic pesticides, there are some heavy-duty insecticidal chemicals for controlling Lily Leaf Beetles. The insecticides carbaryl (Sevin) and malathion are effective on adults and larvae. However, carbaryl is highly toxic to bees and malathion is also toxic to many non-target insects.
Links For further reading:
Lily Leaf Beetle Life Cycle –a good description.
Ottawa Orchid Society’s Fact Sheet on Neem – the best overview information source I found - and it’s local!
Full Instructions for using BIONEEM® - from Safer’s – one supplier's instruction sheet
Effect of an Azadirachtin Formulation on Six Nontarget Aquatic Macroinvertebrates – information on being cautious not to contaminate water bodies.
Natural Products for Insect Pest Management – a good overview document on botanical insecticides from the University of Florida
Note: The Reilly's use least toxic practices available to maintain healthy plants both for their nursery-sold plants and in their gardens. This is quite different than broadly promoted Integated Pest Management practices which, while attempting to reduce the use of toxic chemicals, still relies heavily on many chemicals viewed with suspicion by concerned environmentalists. Phil has always been 'one of those environmental activist' and he carries his concerns and actions into the family's nursery business.
