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Contents:
Pests and Beneficials in the Orchard
Natures Balance: Good Bugs and Bad Bugs
Insect Identification and Life Cycles
Attracting Good Bugs
Pests and Beneficials in the Orchard
Many, but not all, 'bugs' are insects. Insects are those animals belonging to the phylum Arthropoda – animals that have a hard external skeleton and many-jointed legs – and class Insecta – animals with an adult form that has a chitinous exoskeleton, six legs, and wings. Spiders, daddy long-legs, mites, ticks, scorpions, centipedes, millipedes, and earthworms are each important in the orchard, but are technically not insects. Other animal life such as birds and mammals (squirrels, mice, etc.) also play a role in the orchard ecosystem.
Natures Balance: Good Bugs and Bad Bugs
Among the nooks and crannies of our gardens, there's a silent, relentless war in progress. Without the unsung heroes of this war, the predatory and parasitic insects, we would be over our heads in a mass of bugs. It's been estimated that in one year a single adult aphid, left unchecked by nature's ecological controls, would bury the earth a mile deep in new aphids!
Biological Balance Begins with Diversity
I believe in the underlying premise of organic, or biological, horticulture:
diversity furthers health. The more variety a landscape has, the more sustainable
it can be. The insects we call "pests" live in dynamic interplay with the
surrounding environment. Insects cannot be eliminated entirely, nor should
we wait to eradicate them. Even pests are essential to the scheme of things,
for without pests, the predatory and parasitic insects would not be able to
reproduce. Nature doesn't eradicate insects, but maintains, instead, a kind
of balance between the opposing sides.
Since pest problems are community related, a single insect does not always mean a problem, nor does it require a program of "control." A classic case is aphids. When my clients spot a couple of "the dread aphids," they call on me to bring forth every weapon at my disposal for eradication. Much to their surprise, my first suggestion is to wait and watch. In my experience, aphids are not a problem until they reach certain numbers. Sometimes the population never gets to what I would consider a threatening level. On many occasions, I could point out to the client a number of bloated and empty aphid bodies called mummies. These are a result of parasitizing by the larvae of a tiny wasp of the family Chalcidoidea. Parasitized aphids indicate to me a healthy balance between the aphid and parasitic wasps. Almost any spray, whether botanical or synthetic, would greatly reduce the population of the parasitic wasps.
Good Insects – Predators and Parasites
Insects have devised many ways to eat other insects. There are predators,
those that eat insects; and parasites, or parasitoids, those that deposit
an egg within the insect (or host) from which a larva emerges to devour the
host's innards.
Predators don't waste time - they attack and devour. As consumers of insects, parasites take much longer. For example, after a braconid was plays eggs inside a tomato hornworm, it takes many days for the larvae to mature. If the larvae were to eat too fast, they would run out of food before they became adults. The parasitoids are very useful in your edible landscape as persistent search-and-destroy teams, always at work looking for pesky invaders.
As adults, female parasitoids need a high-energy fuel as they fly from place to place looking for hosts. They eat nectar, pollen, sap, and the honeydew of insects. The parasitic insects can be encouraged by providing the concentrated energy they need - primarily by growing plants that offer lots of pollen and nectar. Happily, many predators also need an abundant supply of pollen and nectar to fuel their searching activities.
Recognizing Adults and Larvae
It is important to be able to identify both adult and larva stages of predatory
insects. When I first started looking at insects, some looked so ugly that
I assumed they must be bad. Many of the people in the workshops I lead start
out with the same mistaken assumption. Here's a cautionary example: the ladybug
larva is a warty, spiny, sluglike creature often assumed to be a pest by uninformed
gardeners. But the larva does nearly as much damage to real pests as the adult
and ought to be encouraged in your landscape.
Another example is the snakefly (Apulla sp.). With its long, skinny neck and large, imposing head, the adult snakefly looks like a miniature dinosaur, but it is a helpful predator, stalking smaller bugs. Or take the green lacewing. The adult stage is a beautiful, delicate-winged insect. The undeniably ugly alligator-shaped larva has prominent needlelike jaws and a voracious appetite for insects.
Among the predators you ought to know and cultivate are ladybug beetles, predatory mites, bigeyed bugs, damsel bugs, minute pirate bugs, crabid beetles, robber flies, and green lacewings. They will help maintain a healthy ecological balance in your edible landscape.
General and Specific Eaters
Some beneficial insects have very specific diets, while others will eat much
that crosses their path.
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Other general predators include tachinids, ichneumonids, minute pirate bugs, big-eyed bugs, assassin bugs, collops beetles, damsel bugs, earwigs (the endemic earwig, not the European earwig, which eats our young seedlings and plants), ants (yes, again, in certain situations; other times, they "farm" aphids!), lygus bugs, and anthicid beetles.
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Biological Balance Means Good Diversity
A healthy ecosystem develops only when you carefully choose the plants in
your edible landscape. There is good diversity, diversity that makes little
difference, and bad diversity. For example, you wouldn't put in plants that
attract aphids and others that help control aphids. Some weeds (such as plantain
- Plantago sp.) improve the soil, yet these same weeds may attract
pests (aphids) that can damage your apple trees by providing a favorite food
and a winter habitat for rosy apple aphids. Polyculture - growing many types
of plants in the same landscape - makes for diversity and tends to protect
crops if you carefully select the plants.
Using Trap Plants to Regulate Pests
Using plants to reduce pest problems requires you to know what mechanisms
are at work and to accept the risk that things may not go as planned. Consider
the use of nasturtiums in the landscape. They are listed in traditional companion
planting charts as repelling aphids on broccoli and other cabbage family members;
yet I have often noticed high populations of aphids on nasturtiums - they
are among the first plants to be infested in spring. The nasturtium appears
to me, in this case, to be a favorite host, acting as a trap plant, not as
a repellent. Nasturtiums also have a possible role as nurse plants for the
beneficial predators of aphids.
Whatever the truth, nasturtiums sound good on paper, and they work in certain situations; but there is a risk that the aphids they feed will migrate to nearby crops. Sometimes a colony of wingless aphids gets so crowded that it gives birth to winged young that ride the breeze to look for greener pastures.
Trap plants are a double-edged sword. They are not so delectable that they literally trap the pests for the whole season; but they can also act as nurseries for beneficial insects.
Using Nurse Plants to Regulate Pests
Even a crop plant can act as a nurse plant for beneficial insects. One spring
at the Farallones Institute Rural Center, I followed a colony of aphids from
crop to crop. It started on the fava beans as the pods filled out. The top
6 inches of many plants were covered with a black mass of aphids. Four types
of beneficial insects soon showed up - ladybird beetles and their larvae,
soldier beetles, parasitic wasps, and syrphid fly larvae. After many weeks,
the aphids moved en masse to snow pea plants that were beyond the peak of
production.
The fava bean plants produced an abundant crop. The beneficial insects and
their progeny soon found the new location of the aphids.
There are a number of ornamental and uncommon plants that support high populations of pests without any significant problem. As an example, I have seen oleander shrubs blackened by scale and aphids without any sign that the oleander suffered, I also saw no any aphid problems in the adjoining landscape (as a drought-resistant evergreen plant, an oleander is a good candidate for a nurse plant in the perimeter hedgerow or windbreak).
Sow thistle (Sonchus sp.) is a common "weed" in most landscapes around my county. It is one of the first places each spring that I spot beneficial insects eating and parasitizing aphids. Since the plant is easily controlled, I always leave some sow thistle to grow through the winter to act as an early spring nurse plant.
Another possible nurse plant for out-of'-the-way places is stinging nettle (Urtica dioica). (Beware, nettle can become a very tenacious weed. A good design strategy is to plant it in a moist soil at the base of a slope or hill, making sure there is a zone of very dry soil between the nettles and the rest of your landscape.) This moisture-loving perennial is best known for leaving a fiery sting on the legs of wandering hikers, but it is also a hardy herbaceous plant that harbors no important pest or pathogen of common vegetables. One particular aphid feeds on stinging nettle, but not on food crops. A study done in England found that eleven types of predators and parasites fed upon the nettle aphids. The populations of the predators and parasites increased in late April and early May, prior to the increase of pests in the nearby fields, building a reserve of beneficial insects. While the results were not conclusive, it appears that cutting the nettles at the right time would force some of the beneficial insects (for example, ladybird beetles) onto the crop.
Studies are underway in this country with corn spurry (Spergula aruensis) as a nurse plant for syrphid (hover) flies. This well-behaved weed does not compete with the main crop, it is easy to eliminate, it helps develop a loose soil structure, and it can be mowed and fed to cattle. Corn spurry harbors innocuous aphids that the hover flies feed on. Once the population of hover flies increases, it can then move out into the landscape in pursuit of aphids that colonize food crops. To be on the safe side, use the plants that you know are preferred by pests around the perimeters of your landscape. Intercropping is risky. Be prepared to step in with a botanical spray if you think the pests are migrating to nearby crops, or simply cut the infested plants and add to a fresh, hot compost pile.
Borror, Donald, and White, Richard. A Field Guide to the Insects. Boston: Houghton & Mifflin, 1970. My favorite insect reference since the bug collecting days of my youth.
Carr, Anna. Color Handbook of Garden Insects. Emmaus, PA: Rodale Press, 1979. An excellent color reference, with brief suggestions for pest management. Best for Eastern and Midwestern gardeners-gives poor coverage of insects of the Western U.S.
Metcalf, C.L., Destructive and Useful Insects. New York: McGraw-Hill, 1962. An early review of good bugs and pests. Your library may have a copy.
Philbrick, Helen, and Gregg, Richard. Companion Plants and How to Use Them. 8th ed. Old Greenwich, CT: Devin-Adair, 1976. One of the original sources of companion planting information. Contains some good information, but I find many of the folklore-based recommendations to be untrue or inappropriate.
Philbrick, Helen and John. The Bug Book. Charlotte, VT: Garden Way Publishing, 1974. A good, no-nonsense book on safe, organic methods for pest control. Well worth purchasing.
Riotte, Louise. Carrots Love Tomatoes. Pownal, VT: Garden Way Publishing, 1984. The most popular book on companion planting. (Formerly Companion Planting for Successful Gardening. Few scientific studies are cited. Riotte's recommendations overlap and sometimes contradict the Philbricks' in Companion Plants and How to Use Them.
Rodale Press. The Encyclopedia of Organic Gardening. Emmaus, PA: Rodale Press, 1978. The bible for organic gardeners. Sometimes too wordy, sometimes too lean; still, a must for every edible landscaper's library.
Reprinted with permission from:
Designing and Maintaining Your Edible Landscape Naturally, by Robert
Kourik. Metamorphic Press, 1986. To order write to Box 1841, Santa Rosa CA,
95402. OR call (707) 814-2606. $50 + $5 shipping.
Insect Identification and Life Cycles
Insects go through different stages of development, and different species
may look very similar. A basic understanding of their life cycle and careful
observation is necessary in order to distinguish between destructive insects
and beneficial insects. This distinction is important in order to avoid accidentally
eliminating insects that help to control pests.
Promptly and effectively dealing with an insect problem before it gets out
of control can make your life as an orchardist much easier, since many insect
pests are most vulnerable to controls during specific times in their life
cycles, especially during the soft-bodied larval 'worm' stage. Additionally,
the effectiveness of some controls depends on precise timing with insect's
lifecycle; some insect pests are easily eliminated during the immobile egg
or pupal stage, before they reach the destructive larval and adult stages.
Consider purchasing an insect identification guide with information on pests and beneficials such as The Organic Gardener’s Handbook of Natural Insect and Disease Control (see References and Recommendations).
Basic insect body parts:
The insect life cycle:
All insects undergo 3 basic stages of development: egg, larva, and adult.
In passing from the larval to the adult stage, insects undergo metamorphosis
(physical transformation). There are two type of metamorphosis, gradual and
complete.
In gradual metamorphosis, the larval stage resembles adult except that it is smaller and lacks wings and sex organs. The larva eventually sheds its outer shell to accommodate growth (examples: aphids, mites, scales, and grasshoppers).
In complete metamorphosis, the larval stage is wormlike, bearing no resemblance to the adult, and is followed by a pupal stage (a resting stage inside a cocoon or chrysalis) and emergence (examples: butterflies, moths, beetles, wasps, and flies).
Insect Pests and Beneficials:
It is during the larval (worm-like or immature) stage that insect pests are
most destructive to plants as well as most vulnerable to control methods.
During the adult stage, insect pests are harmful in that they lay eggs, causing
their populations to soar. Insect pests damage orchard plants directly
through eating, burrowing, or laying eggs, and indirectly by damaging
leaves (eating leaves or sucking sap) or wood (eating, boring), thereby weakening
the tree.
"Beneficials" earn their title by killing plant-eating insect pests. Some are effective only during their adult stage. Others are effective only during their larval stage. A few are effective during both stages. It is important to time the release of beneficial insects so that their effective stage coincides with the pests' vulnerable stage. When their prey is unavailable (not present at all or in the wrong stage of development), beneficials eat the nectar of certain small-flowered plants (weeds, herbs, and vegetables in the umbelliferae and compositae families). To encourage beneficials to remain in the orchard, some of these plants must be present as an alternate source of food. Generally, if you create an environment that encourages beneficials, you won't need to purchase them, as they will come on their own. If you choose to purchase beneficials, release just a few each day if possible, as most will leave if there is not enough food and water to support a large population.
Non-insect pests and beneficials:
Pests: Squirrels are a significant destroyer of stone fruit and even
apples and pears in urban areas, sometimes devastating entire plantings. Mice,
which can girdle unprotected fruit trees in winter, are more problematic in
wild areas away from human sources of food (i.e. garbage) as they generally
only eat bark as a last resort. Birds can be a major pest, devouring cherries
and berries, but also eat insect pests.
Beneficials: Spiders are one of the most important non-insect beneficials in the orchard. Most are hunters rather than web spinners. Birds have a voracious appetite for both pests and beneficials, but also eat fruit. Toads eat lots of insects as well.
Biodiversity attracts beneficials much better than a uniform lawn. Adding a wildflower garden with a water supply, bird feeders, suet, bird houses, and for toads, an overturned clay pot with an opening in the side will help if an area is mostly grass rather than meadow.
You can lure beneficial insects to your place without using pests as bait, by growing flowers that fuel the search and destroy missions of good insects. Insectary plants can serve more than just the function of pest control; some are edible, some colorful, and some fragrant.
Types of Flowers That Attract Beneficial Insects
Most beneficial insects need a high protein, high sugar food, and most parasitic
insects and predators have short mouthparts that cannot reach far into a flower
for nectar and pollen. Small flowers, their pollen and nectar within reach,
are preferred by many beneficial insects. Two major categories of flowers
fit their needs - the sunflower and parsley families.
Umbellifers
Parsley belongs to the Umbelliferae family (recently renamed the Apiaceae
family), plants distinguished by many tiny flowers arranged in clusters, with
the clusters arranged in an umbel, an umbrella shape.
Vegetables in this family include carrots, parsnips, parsley, celery, celeriac, and Florence fennel. The common herbs - dill, cumin, anise, coriander, and caraway - belong to this family. Some uncommon herbs in the Umbelliferae family include: gotu kola, lovage, angelica, chervil, and skirret. Some wild or native umbellifers include poison hemlock (Conium maculatum); water hemlock (Ciculta douglasii); Queen Anne's lace, or wild carrot (Daucus carota); toothpick weed (Amni uisaga); and cow parsnip (Pastinaca satiua).
As a group, umbellifer flowers produce large amounts of nectar for short periods of time. Each flower quickly fades, but the entire cluster blooms for some time (although for a shorter period than many plants in the sunflower family). Most of these plants produce thousands of seeds each year and are quite invasive if not tended to.
Composites
The members of the sunflower family (recently renamed the Asteraceae family)
are classified as composites and have many tiny flowers arranged together
in one large cluster or composition. Artichoke, lettuce, endive, salsify,
chicory, edible chrysanthemum, cardoon, sunflower, dandelion, and Jerusalem
artichoke belong to this family. The herbs that belong to this family include:
yarrows, artemisias, elecampane, feverfew, costmary, and tansy. There are
hundreds of varieties of ornamental plants in this family, among them marigolds,
zinnias, thistles, asters, calendulas, and gazanias.
While the flowers of a Compositae have less nectar than those of Umbelliferae, the flower heads mature over a longer time, prolonging the flow of nectar. I like to think of the sunflower family as providing the "background music" for attracting beneficial insects. The parsley family provides the "percussion" for emphasis at times during the year.
Flowers at the Right Times
From midsummer until early fall, a landscape with any variety at all has plenty
of sources of nectar and pollen available. The difficult time is early spring.
Aphids awake from winter quite early and function well at temperatures as
low as 45 degrees Fahrenheit or less. It takes some searching and experimenting
to find insectary plants that bloom early enough to overlap with the early
spring aphid "bloom." In my area, there are very few umbellifers and not many
composites in bloom before May. The best umbellifer for early bloom, in the
coastal hills around my house, is the cow parsnip (Pastinaca satiua). This
poisonous plant has a glorious pure white umbel and is the first of the umbellifers
to attract quantities of parasitic wasps. Sometimes the temperatures are so
cool while the cow parsnip is blooming that the parasitic wasps are not active,
even though the aphids are breeding faster than rabbits. Each year beneficial
insects arrive at different limes, but there is usually something on the cow
parsnip flowers that eats or parasitizes aphids.
Some members of the composite family that bloom around my house in early spring are gazanias, African trailing daisies, and calendulas, but I have not seen many bugs gathering on these flowers, certainly far fewer than on a cow parsnip flower head. I planted thousands of square feet of African trailing daisies when I was a landscaper and never noticed many insects visiting the blossoms.
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Reprinted with permission from:
Designing and Maintaining Your Edible Landscape Naturally, by Robert
Kourik. Metamorphic Press, 1986. To order write to Box 1841, Santa Rosa CA,
95402. OR call (707) 814-2606. $50 + $5 shipping.
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