Insect Perceptions, Irrelevant or Important

February 23, 2016

“IT WAS THE BUTTERFLIES, my people say, who brought the first human babies to their feet,” writes Canadian Richard Wagamese in “Butterflies Teachings,” an essay touching on “what’s called Enendamowin, or Ojibway worldview” in his brilliant collection, One Native Life. “Before that, the New Ones sat in innocence beneath a tree, watching the world around them with wonder. But Creator had planned more for them. Their destiny called for them to move throughout the world. These human babies were meant to walk upon their two legs, and as long as they sat under that tree their destiny could not be fulfilled…The air seemed to tremble with butterflies. The human babies were entranced. Each time they tried to snare a handful of colour, the cloud drifted away. They stretched their arms higher. They thrust out their hands. But it was to no avail. When the butterflies danced just out of reach a final time, the New Ones lurched to their feet and raced after them across the meadow. The Animal People celebrated quietly, then returned to their dens and burrows and nests. The human babies never caught those butterflies, but they kept on running, right into the face of their destiny…”

Quite a different worldview from Prague and Eastern Europe, where Franz Kafka’s famous novel Metamorphosis begins: “As Gregor Samsa awoke one morning from uneasy dreams he found himself transformed in his bed into a gigantic insect.” According to the “wall notes” in the exhibit “Disguise: Masks & Global African Art” at the Fowler Museum at UCLA, Kafka’s words inspired South Africa artist Walter Oltmann. Among neon masks, dancing mask videos and sculptured African animals wearing masks are Oltmann’s large anodized aluminum and brass wire caterpillars in the midst of “transformation and change” (metamorphosis) and fashion sketches titled “Beetles & Suits.” The suit coats are gracefully curving, shell-like beetle elytra (outer wing covers) fashionably topped off with the latest antennae, and looking both business-like and sci-fi out of Star Wars or Star Trek at the same time. I can easily imagine a cell phone age makeover of The Beatles’ Sgt. Pepper’s Lonely Hearts Club Band regalia and long hair with “beetle suits” and high-fashion antennae. Perhaps too much entomology affects the psyche. Oltmann writes that “spending an inordinate amount of time on making something that is usually considered insignificant like an insect, does make us look differently at them.” He says it “speaks of neither this nor that,” but I’m not so sure.

Insect observations appear in haiku by Japanese master Matsuo Basho, whom I think of as the late 1600s slightly more refined counterpart of 20th century Los Angeles poet Charles Bukowski, who was too busy with “other interests” to notice beetles, flies, mosquitoes and roadside weeds. In Moon Woke Me Up Nine Times: Selected Haiku of Basho, translator David Young writes: “Odd numbers predominate; a dance is occurring, and each third of the poem is a turn, a gesture, a refining or revelation… The poem seems to end almost as soon as it has begun, a small flash of lightning…A more literal version of the haiku cited (below) would be something like: What can save your life? / one leaf, with an insect / sleeping on its journey… the journey, which refers to a Chinese story that Basho’s readers would know but that is largely meaningless to English readers…‘Basho mash-ups,’ I have sometimes called my versions”:

One insect
asleep on a leaf
can save your life

Perhaps Basho was thinking of medicinal silkworms slumbering on mulberry leaves, or perhaps his mind was journeying among high mountains where ghost moths metamorphose with fungi into plant-animal hybrids that have been used in Asian medicine for centuries. David Young says about haiku: “They love to startle, first the writer and then the reader. As though a hummingbird were to land suddenly on your resting arm. It is the way the world so often surprises us.”

A haiku by Los Angeleno Mark Jun Poulos, whose observation of the seemingly mundane urban habitat nagged at me long after I thought I had dismissed its ordinary elements from consciousness:

restroom sink-—
ladybug cooling off
in a drop of water

What nagged at me was water, a vital ingredient of life, which as hard sprays of rain washes away pesky mites and aphids that are ladybug prey. Water (H2O) is also a missing ingredient in most ecological studies of interplanting, a habitat diversity strategy designed to boost populations of lady beetles and other beneficial insects providing natural pest control. Australian grape vineyards and California lettuce fields have had some success interplanting blooming rows of sweet alyssum to provide pollen, nectar and alternative prey for ladybugs, lacewings, hover flies and other beneficial species consuming aphids and other pests. Sweet alyssum is also host to micro-wasps helping Michigan asparagus growers by parasitizing leafmining pest insects, Amanda Buchanan of Michigan State University reported at the Entomological Society of America (ESA) annual meeting in Minneapolis. But if habitats are missing water, then perhaps lady beetles, which do not puncture plants to drink fluid, will leave to find restroom sinks, puddles or other water sources. Perhaps, like providing water bowls for pets, something similar needs to be researched as part of biological control habitat alternatives. Though I would draw the line at alcoholic drinks, except perhaps beer in snail and slug traps. Another urban haiku observation by Mark Jun Poulos:

sultry afternoon—
wasp hovers over a whiskey bottle
held by a drunk bum

Ethanol or ethyl alcohol, by percentage the main chemical component of distilled whiskey, should not be abused, nor perhaps should it be so heavily subsidized as a biofuel, as that incentive exacerbates huge landscape changes measurable as reduced biodiversity. At Synergies in Science, a rare Minneapolis gathering of the ESA, American Society of Agronomy, Crop Science Society of America and Soil Science Society of America, the diminishing biodiversity of a Midwest USA with 21% less wheat, 16% less hay and much more GMO corn to distill into ethanol motor fuels was as hard to ignore as a drunk with a whiskey bottle on an urban bench. Jonathan Lundgren of the USDA-ARS in Brookings, South Dakota said we need to get away from our “very pest-centric approach” and adopt a more holistic biological network approach. Instead of a Midwest saturated with pesticides to grow GMO corn to distill into fuel tank ethanol, something as seemingly simple as adding biodiversity via cover crops amongst the corn rows could produce enough soil biocontrol of corn rootworm to eliminate wasteful neonicotinoid seed treatments whose honey bee and beneficial insect friendliness is being hotly debated. Karen Friley of Kentucky State University reported at the ESA that something as seemingly simple as native plant border rows around sweet corn fields “provide microclimates in the form of moderated temperatures, which offer shelter” for numerous natural enemies controlling corn pests.

Curiously enough, ethanol (alcohol) like that in whiskey bottles and vehicle fuels also attracts pine beetles and ambrosia beetles considered destructive forest, landscape, street tree and nursery pests. Perhaps more curiously, the very trees being attacked are producing the ethanol and releasing it into the atmosphere when stressed (e.g. by drought or flood), decaying or dying. Trees may look perfectly healthy on the outside, but inside the tree is another story, because ethanol emissions are signs of sickliness and ill health. Chemical ecologist Christopher Ranger of the USDA-ARS in Wooster, Ohio said it is a real problem, for example, when nursery seedlings are used to replant spruce forests or with dogwoods, magnolias, pines, etc. in nurseries, backyards, along streets, etc. It is definitely ecology, as the ethanol is luring in the beetles to help “recycle” the trees back into the soil as nutrients.

I liked Ranger’s reasoning: Find the tree equivalent of driver breathalyzer tests as a beetle-attack early warning system. SCRAM wrist bracelets worn by offenders for transdermal drug and alcohol detection were tested, but were not sensitive enough; taking a week to detect low tree ethanol exhalations, whereas beetles detect a few parts per million of alcohol and get to trees almost on day one. The solution was a portable ethanol monitoring device with a detector tube and a plunger to pull in air samples; developed using Japan’s Gas Tech industrial gas leak detection technology for quick detection of “inebriated” trees.

So, which is more startling and surprising: art, haiku or entomology?

Strange brew: September 17, 2015 daylight turning to dark, caught in one of those infamous, almost proverbial L.A. traffic jams at a freeway underpass on Church Lane transitioning from Sunset Blvd to Sepulveda Pass on my way past the Getty Museum to Mulholland Drive, listening to the Moody Blues Live at Red Rocks, going nowhere. Haiku and fireflies flashing internally, and externally the blinking side turn lites and red back brake lights suddenly and surprisingly metmorphosed into synchronous fireflies, albeit of a mechanical or robotic nature:

Tail and Turn Lights
Flashing like Synchronous Fireflies
In the Los Angeles Traffic Jam

 

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Grapes Love Tobacco & Sage

June 13, 2015

GRAPE VINES GAIN and pests suffer when TOBACCO and SAGEBRUSH grow in the same neighborhood. For example, Chinese experiments show that when tobacco roots intermingle with grape roots, vineyards soils are progressively cleansed of the dreaded soil-dwelling phylloxera aphid; the same phylloxera aphid that almost completely destroyed French grape growing in the 1800s, before resistant rootstocks were discovered. In recent decades, the phylloxera aphid has evolved new forms that destroy formerly-resistant rootstocks. But on the positive side, the phylloxera plague in nineteenth century French vineyards was a major catalyst for innovations such as the development of modern scientific agriculture and modern methods for fumigating or disinfesting sick soils.

Tobacco plants get a bad rap today, as the source of abused and addictive products with adverse health effects. But it was not always so, and need not be so today, write David A. Danehower and colleagues in the book, Biologically Active Natural Products: Agrochemicals: “When Columbus first arrived on the shores of North America, he found Native Americans growing and using a plant unknown to Europeans. This plant held great spiritual significance to Native Americans. Scientists who followed in the footsteps of the early North American explorers would later name this plant tobacco. Tobacco (Nicotiana tabacum) farming began in the early 1600s near the Jamestown colony in Virginia. As the use of tobacco products for smoking, chewing, and snuff was promoted in Europe, tobacco became a leading item of commerce between the colonies and England. Notably, George Washington and Thomas Jefferson both farmed tobacco. Thus, the history of America is inextricably linked with the history of tobacco production.”

The specific idea of interplanting tobacco with grapevines to control soil pests like phylloxera aphids is apparently a recent Chinese agricultural innovation. Why no one thought of it before is a mystery, as nicotine from tobacco plants has a long history as a fumigant and sprayed insecticide; and more recently sweet “sugar esters” (fructose, glucose, fatty acids) have been singled out from among the several thousand chemical compounds in tobacco as “new” natural insecticides (some fungi and other microbes are also killed). Perhaps agricultural tradition plays a role, as the Chinese have an ancient agricultural heritage that includes pioneering biological pest control (e.g. predatory ants to control citrus orchard pests) and routinely interplanting compatible plants for their pest-fighting and mutually beneficial effects. Of course, growing cover crops and beneficial insect plants like sweet alyssum in grape rows is becoming more common. And since ancient times, the Mediterranean areas of Europe and the Middle East have had grape vineyards interspersed with oaks (corks, barrels for wine grapes), olive trees and crops such as wheat. But never before has tobacco been grown among grape vines to control soil pests. Indeed, modern farmers seem to favor pumping liquid chemicals and volatile gases into the soil to combat soil pests.

Perhaps as close as a nineteenth century French grape grower came was Bernardin Casanova of Corsica, France, who in 1881 patented a liquid mixture of grape distillates, Corsican tobacco, spurge, laurel, grain straw, burnt cork and soap that was rubbed and poured on the base of grapevines to kill phylloxera. In California, which has native plants that are every bit as insecticidal as nicotine from tobacco, the only anti-phylloxera interplanting seems to have been new resistant rootstocks to eventually take the place of the old. In essence, a concession of failure and a starting over with new rootstock (and pulling out the old phylloxera-infested vines).

Like Mr. Casanova in nineteenth century France, the modern Chinese researchers started out with a watery solution containing tobacco; but in a bit more scientific fashion with controlled tests of the tobacco solution on young greenhouse-grown grape vines. “The results showed that aqueous extracts of tobacco had certain alleviating effects on phylloxera infection,” according to a 2014 abstract from the journal Acta Entomologica Sinica. “Both the aqueous extracts of tobacco at the concentration of 20 mg/mL and 50 mg/mL had an inhibition to phylloxera infection,” with a 50% reduction in phylloxera infection within 3 weeks (along with a reduction of fungal invaders that kill injured grape roots).

Chinese tobacco-grape laboratory and field studies were also reported in the Journal of Integrative Agriculture in 2014. The lab studies indicated that tobacco extracts in water were indeed a valid herbal (botanical) remedy against phylloxera aphids. In three years of field tests with tobacco interplanted in infested grape vineyards, phylloxera infestations of grape roots steadily decreased each year. “Tobacco was used as the intercropping crop because it includes nicotine, which is a source of bio-insecticides,” said the researchers. “The production of new grape roots was significantly higher in the intercropping patterns than in the grape monoculture in 2010, 2011 and 2012, and the vines gradually renewed due to the continuous intercropping with tobacco over three years…The results indicated that the secondary metabolites of tobacco roots had released to soil and got to the target pest.” Tobacco intercropping effects on grape plants was also measurable in terms of “cluster number per plant, cluster weight, cluster length, cluster width, berry number per cluster, mean berry diameter in the mid portions of the cluster, carbohydrate content, fruit color index, leaf width and branch diameter.” The researchers expect that this “Successful intercropping with tobacco” will stimulate more research with other insecticidal plants to disinfest vineyard soils.

We could probably end the blog item here, or have a second article as part II, but we have some interesting interactions among sagebrush and tobacco plants that can spillover to grape vineyards. Oddly enough, sagebrush and tobacco seem to get along very well. According to M.E. Maffei, writing in the South African Journal of Botany: “Aerial interaction of the wild tobacco (Nicotiana attenuata) and sagebrush (Artemisia tridentata subsp.) is the best-documented example of between-plant signaling via above-ground VOCs (Volatile Organic Compounds) in nature.” Wounded or “Clipped sagebrush emits many volatiles, including methyl jasmonate, methacrolein, terpenoids, and green leaf volatiles.” These sagebrush volatiles (VOCs) stimulate nearby tobacco plants to become less hospitable to caterpillar pests (fewer in number). The process is called priming and results in plants producing more chemicals deleterious to pests. For readers desiring all the details and more theory: In 2006, Kessler et al. published in a journal called Oecologia under the title “Priming of plant defense responses in nature by airborne signaling between Artemisia tridentata and Nicotiana attenuata.”

Big Sagebrush, known scientifically as Artemisia tridentata, is a native North American plant that can reach 4 meters in height and live from 30 to over 200 years in arid desert environments by using hydraulic lift to pump water from deep soil layers. The plants are a rich and underutilized source of medicinal compounds, insecticides, fungicides, natural preservatives, etc. Worldwide there are at least 500 Artemisia sagebrush species, many used in traditional medicines (e.g. China), cosmetics, insect repellents, and as spices and flavorings in foods. For example, Artemisia annua has attracted attention to combat malaria. Readers desiring a crash course in Artemisia species and their bio-active essential oils will find it online in an excellent 24-page review article in a journal called Molecules.

Big Sagebrush is “found in arid regions of North America from steppe to subalpine zones, dry shrub lands, foothills, rocky outcrops, scablands, and valleys,” wrote Christina Turi and colleagues in 2014 in the journal Plant Signaling & Behavior. “Traditionally, species of Big Sagebrush have been used as a ceremonial medicine to treat headaches or protect individuals from metaphysical forces. A total of 220 phytochemicals have been described in A. tridentata and related species in the Tridentatae. Recently, the neurologically active compounds melatonin (MEL), serotonin (5HT), and acetylcholine (Ach) were identified and quantified.” In other words, sagebrush plants and human brains and nervous systems have a lot in common.

Indeed, galanthamine, a botanical drug treatment for mild to moderate Alzheimer disease, can also be used to “treat” sagebrush. Galanthamine, which is named after the snowdrop plants (Galanthus species) where it was discovered, is also found in Narcissus and other common bulbs. Galanthamine is, according to researchers Turi et al., “a naturally occurring acetylcholinesterase (AchE) inhibitor that has been well established as a drug for treatment of mild to moderate Alzheimer disease.” Why bulb plants produce chemicals affecting both Alzheimer disease (human nervous systems) and sagebrush plants is a good question. One theory is that plants release these chemicals into the environment to communicate with and influence the behavior of other plants, and also perhaps deter or otherwise influence herbivorous animals. Environmentalists, overly preoccupied with worries about carbon dioxide and GMOs, might ponder the fact that human chemicals with medicinal effects released into the environment might be the bigger threat, affecting plants and ecosystems in ways not yet fully appreciated that may comeback to bite us.

The Western USA is known for its vast expanses, perhaps 50 million acres with Big Sagebrush, some of which is being displaced for vineyards in isolated valleys in the Pacific Northwest. I particularly like the description of the Big Sagebrush ecosystem at the Sage Grouse Initiative: “To many of us, sagebrush country symbolizes the wild, wide-open spaces of the West, populated by scattered herds of cattle and sheep, a few pronghorn antelope, and a loose-knit community of rugged ranchers. When you stand in the midst of the arid western range, dusty gray-green sagebrush stretches to the horizon in a boundless, tranquil sea. Your first impression may be of sameness and lifelessness—a monotony of low shrubs, the over-reaching sky, a scattering of little brown birds darting away through the brush, and that heady, ever-present sage perfume.”

About 90% of the native sagebrush steppe habitat in the eastern Washington grape growing area was removed to make way for the vineyards. But the 10% remaining sagebrush habitat may have important ecological benefits, such as improved natural or biological pest control in the vineyards. One suggestion is to leave some of the native Big Sagebrush around vineyards, for its beneficial ecological effects. “Perennial crop systems such as wine grapes have begun using cover crops and hedgerows to increase beneficial insects and promote sustainable vineyard management in areas like New Zealand and California,” Washington State University researcher Katherine Buckley told the 2014 Entomological Society of America (ESA) annual meeting in Portland, Oregon. “However, in arid wine growing regions such as eastern Washington, cover crops are often prohibitively expensive due to water costs. We wanted to determine if native plants, which require little or no irrigation, could be used to increase beneficial insects and enhance conservation biological control of vineyard pests in eastern Washington.”

The native sagebrush steppe ecosystem has a wide range of plants, but is characterized by species such as big sagebrush (Artemisia tridentata), rabbitbrush (e.g. Chrysothamnus, Ericameria spp.), bitterbrush (Purshia spp.) and perennial bunchgrasses (e.g. Agropyron, Stipa, Festuca, Koeleria, Poa spp.). The Big Sagebrush ecosystem is richer in species than meets the eye at first glance. Over 100 species of birds (e.g. sage grouse, sage thrasher, sage sparrow and Brewer’s sparrow) forage and nest in sagebrush communities, and they could provide a lot of insect biocontrol at less cost and with less environmental impact than chemical sprays.

A U.S. Forest Service report called Big Sagebrush a keystone species and “a nursing mother” to “31 species of fungi, 52 species of aphids, 10 species of insects that feed on aphids, 42 species of midges and fruit flies that induce galls, 20 species of insects that parasitize the gall inducers, 6 species of insects that hibernate in big sagebrush galls, 18 species of beetles, 13 species of grasshoppers, 13 species of shield-back katydids, 16 species of thrips, 74 species of spiders, 24 species of lichens, 16 species of paintbrushes, 7 species of owl-clovers, 5 species of bird’s beaks, 3 species of broom rapes, and a host of large and small mammals, birds, and reptiles.”

“After locating vineyards with some form of native habitat restoration in four different growing regions of eastern Washington, yellow sticky traps and leaf samples were used to monitor beneficial and pest insect numbers in the habitat restored vineyards and nearby conventional vineyards over a three year period,” said Buckley. The native plants, which are adapted to the region’s hot summers and cold winters, are home to at least 133 insect species. Native habitat vineyards had fewer pest insect species; and higher populations and a higher diversity of beneficial insects. Anagrus wasps, which are known to parasitize pesky grape leafhoppers, were most abundant in Big Sagebrush. More amazingly, this leafhopper biocontrol wasp was found year-round in Big Sagebrush, even when the plant was not flowering. No other plant, not even the photogenic wild roses planted at the end of vineyard rows and admired by tourists, hosted the tiny leafhopper biocontrol wasp year-round.

Garden herbs such as thyme (Thymus ssp.), mugwort (Artemisia ssp.) and fennel (Foeniculum ssp.) have all been tested in vineyard interrows because they are fungicidal against Botrytis cinerea, a fungus attacking grape clusters, and boost soil micro-nutrients like copper, manganese and zinc. Maybe at some point in time, the Chinese interplantings of tobacco and alternating strips of Big Sagebrush (or other Artemisia species) and garden herbs will all get integrated together with other cover crops and native hedgerows into grape vineyards for a more biological or natural approach to agriculture. With sagebrush and tobacco, we have only scratched the surface of vineyard possibilities.


Pheromone Revolution Hits Half Century Mark

October 7, 2009

HALF a CENTURY ago the PHEROMONE REVOLUTION commenced in earnest. German chemist Adolf Friedrich Johann Butenandt opened the floodgates as lead author of an article announcing the isolation and chemical identification of a sex pheromone female silkworm moths produce to attract male mates. Butenandt had already shared the 1939 Nobel Prize in chemistry for discovering human reproductive steroid hormones. So the 1959 article announcing the first pheromone in the monthly chemical science journal Zeitschrift für Naturforschung B (14B:283-4) attracted the attention of Rachel Carson and stimulated the efforts and imaginations of many others searching for insecticide-reducing alternatives.

HALF a MILLION virgin female silk moths were sacrificed over a span of almost THREE DECADES to identify that first sex pheromone, named bombykol because Bombyx mori is the scientific name of the Chinese silk moth of textile fame. In the past half century, thousands more pheromones have been identified, mostly from pest insects of economic interest. But also increasingly from beneficial insects providing biological control.

According to researchers like Jeffrey Aldrich at the USDA-ARS Chemicals Affecting Insect Behavior Laboratory (CAIBL) in Beltsville, MD, the potential applications of natural enemy pheromone and semiochemical research, such as herding beneficial insects into crop fields where they are needed, is still in its infancy. Projects include using pheromones to increase biocontrol by predatory spined soldier bugs (Podisus maculiventris). These beneficial stink bugs are capable of biologically controlling pesticide-resistant Colorado potato beetles, Mexican bean beetles, and cabbage and tomato caterpillars.

One idea is using pheromones to trap natural enemies, and then creating mini-insectaries by placing cages full of natural enemies into crop fields and landscapes. Predator production can be maximized with “an in-field nursery where we are putting these trapped bugs right inside of the (mesh) cage” over plants in the field, said Aldrich. “You pick a mesh size where the adults can’t get out, but when they lay eggs then the nymphs can walk out and start feeding on pest species in the vicinity.” In field tests, potato defoliation was reduced and yield significantly increased.

In bean field tests, spined soldier bug nymphs walked upwind towards an aggregation pheromone. In sequential plantings, this technique could be used by farmers to move or herd predators out of maturing fields into more newly planted fields. Pheromone technologies are also being explored to maximize biocontrol by minute pirate bugs, big-eyed bugs, tachinid flies, and other natural enemies.


Planet Moth

September 7, 2009

WITH 200,000 known species, Earth is almost Planet Moth. Only beetle species are more numerous. Moths have been denizens of Earth since prehistoric times, long before the ascent of man. Mostly nocturnal, secretive and nondescript, moths play a quiet ecological role, doing some vital pollination of plants and nourishing the food chain by feeding birds, bats, lizards, fish, frogs and many other critters.

Silkworm moths, domesticated as a crop on mulberry trees in China about 5,000 years ago, are famous in the textile industry. Clothes moths are infamous for feeding on garments, and have spurred herbal pest control innovations since ancient times. Humankind has sprayed billions of tons of synthetic pesticides against cotton bollworm moths, Indian meal moths, diamondback moths, cabbage loopers, leafrollers, leafminers, stemborers, codling moths, corn earworms, inchworms, armyworms, spruce budworms, gypsy moths and bagworms, to name but a few. However, alternatives like pheromones are becoming more widely used to monitor, trap, and confuse moths and prevent mating and egg laying (eggs hatch into caterpillars that eat, pupate and beget new moths).

Biocontrol by natural enemies, including birds, bats, toads, spiders and other insects, is part of the ancient planetary rhythm for controlling moths and maintaining global ecological balance. From Texas, Arizona, California and Mexico to China, Russia, Central America and Australia, microscopic Trichogramma wasps are among the most popular insectary-reared natural enemies released to stop moth egg hatching. Cotton growers escaping the pesticide treadmill have traditionally been big users of Trichogramma wasps. Tomatoes, corn, grapes, tree fruits, ornamental nurseries and many other crops also use Trichogramma, green lacewings and a wide array of other natural enemies purchased from Rincon-Vitova and other insectaries to lessen moth attacks and minimize pesticide use.

Of course, the moth wars are not all one-sided. Spray pesticides too often and moths become resistant. And moths can elude and make life challenging for their natural enemies. For example, many moth species respond to bat ultrasound echo-location signals with evasive aerial maneuvers and jamming signals. Moth immune systems may even encapsulate and prevent parasites from providing biocontrol. Each female of one fat Australian moth species can lay 18,000 eggs, the ultimate defense, essentially ensuring survival by sheer numbers.


Beneficials Sweet on Alyssum

July 22, 2009

INTERPLANTING SWEET alyssum (Lobularia maritima) is an excellent way to promote natural biocontrol of a wide array of landscape, orchard, field and garden pests like aphids, stinkbugs, leaf and fruit worm caterpillars, etc. Companion planting has ancient roots, figuring in the writings of the Greek Theophrastus in 300 B.C. and the Roman Pliny (Plinius Secundus) in 1 A.D. Though popular in organic gardening and farming, floral interplants escaped serious scientific scrutiny until recent years.

Australia’s wine grape growers are among those who take their sweet alyssum companion plantings very seriously. At Australia’s EH Graham Centre for Agricultural Innovation ecological engineers and entomologists like Geoff Gurr of Charles Sturt University are fine-tuning companion planting. Firstly, you need to choose companion interplants that supply nectar, shelter and other resources to beneficial predators and parasites but not to pest species.

The Aussies focused their scientific studies on a Trichogramma species parasitizing and destroying the eggs of the lightbrown apple moth (Epiphyas postvittana), a key pest of Australian vineyards. In “clean” vineyards where weeds and ground covers are destroyed by herbicides or cultivation, biocontrol species like Trichogramma may survive as few as two days, versus three days with water only and up to 20 days with sweet alyssum (the best ground cover tested). Alyssum flowers doubled the number of moth eggs parasitized over a 10 day period. In contrast, when the alyssum plants were deflowered the Trichogramma perished and there was little biocontrol.

But there is more to the story. “Not only is plant species important, but the cultivar within the species is critical,” Gurr told an Entomological Society of America annual meeting. For example, Trichogramma survive far longer on white-flowered alyssum cultivars compared to purple and other colors. Alyssum also boosted predators without aiding the apple moths, which was not the case for every ground cover interplant tested.

Most landscape and cropping systems have not been subjected to the same level of ecological and laboratory investigation as Australian wine grapes. Thus, Rincon-Vitova and other insectaries selling beneficial insects generally recommend blends of flowering plants supplying floral nectar throughout the season.