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Here's how to create the perfect environment for pest-eating insects.
BY JOANNA PONCAVAGE
By now, most of you know you can buy ladybugs, Trichogramma wasps or green lacewings and leave them delivered to your garden by UPS. But your backyard is already, home to many native beneficials that show up for free. Getting more of these helpful bugs to stop by-- and stay awhile--might be as simple as creating the right habitat.
The Rodale Institute Research, Center has been working to identify the best plants for such, insets attraction since 1987. They've examined nearly 150 so far, recording the kinds (and numbers) of helpful and harmful insects drawn to them.
Their recommendations take into consideration a plant's ornamental value, usefulness and flowering time, as well as the downside--their potential to become troublesome.
'Preliminary'' findings (research never ends!) will help you to make informed decisions about what you can plant to keep beneficial insects happy. And if you discover something we may have missed, please write and tell us--after all, every gardener is a scientist and every garden is a unique laboratory.
Plants were chosen for testing because they were mentioned in papers written by other scientists, or because staffers noticed they attracted beneficials Some already had a reputation as "butterfly plants,''because butterflies visit them for nectar and pollen Some were chosen because they are widely grown, showy ornamentals. All are easily available from seed catalogs and nurseries.
During the tests, plants were swept regularly with insect-catching nets, and the insects were bagged and frozen for later identification and counting. Particular attention was paid to the following predators and parasites:
· Syrphids, also called hover flies They attack many kinds of aphids.
· Parasitic wasps There are many kinds including Trichogramma . All lay their eggs in the egg, larva or adult form of pests killing them.
· Ladybugs (or lady beetles) They eat a wide variety of other insects, inching aphids
· Lacewings Their larvae feed on aphids, mealybugs and scale, moth eggs and small caterpillars
· Flies Depending on the species, these can be pests or beneficials Despite the bad reputation of the pests, the beneficial varieties, includling tachinid flies, are extremely valuable biological controls.
· Insidious flower bugs. A type of pirate bugs, these feed on small larvae, insect eggs, mites and thrips
· Spiders. These are not insects, but are fierce predators.
Based on the data they have to date, the RIRC researchers believe that the following plants are good candidates for creating habitats that attract and nurture beneficials.
COMPOSITES: These plants ((Compositae) have flowers with a simple ray of petals around a center
·Tansy (Tanacetum vulgare the herb, not Senecio jacobaea or tansy ragwort, the noxious weed) is a large, attractive plant once used extensively in medicine and cooking. In the research center herbary, tansy attracts a kit of beneficials-- one day, there were 115 adults and larvae of two different ladybug species in a 3-by-3-foot plot. Tansy also attracts many insidious flower bugs small wasps, lacewings and flies.
One reason for the plant's popularitv might be that it's full of food--specifically the tansy aphid which feeds by sucking flee plant's juices and which tends to congregate in large numbers in the plant's serrated leaf margins.
If you do decide to grow tansy in your garden position it carefully! This 4- to 5-foot-tall perennial is vigorous and spreading and when conditions are moist and unventilated the honeydew excreted by all those aphids gets moldy and can turn the plant's leaves black.
We hasten to add that tansy's benefits far outweigh these potential problems. A solution made from its leaves has even been found to repel Colorado potato beetles in the laboratory. Tansy can be grown from seed or propagated by division. Seeds are tiny and germination is slow but dependable.
· WHITE SENSATION cosmos
(Cosmos bipinnatus) bears beautiful flowers that are attractive in garden or vase. They also attract lacewings ladybugs insidious flower bugs and spiders. Although visually showier
SUNNY RED cosmos (C.sulphureus) appears to attract fewer numbers of beneficials. White SENSATION cosmos grows 4 to 5 feet tall You can direct seed where you want them to grow or start them indoors for earlier blooms.
Anthemis (Anthemis tinctoria KELWAY) is a 2-foot perennial long valued as a dye plant that attracts beneficial wasps and flies It makes a nice border plant with many showy yellow flowers over a long periods of time. It reseeds itself readily, Both seeds and plants are available
· LEMON GEM marigold (Tagetes tenuifolia also called Signet marigolds; sometimes called T.signata) attracts small wasps and spiders. An easy-to-grow annual that is more cold-sensitive than other marigolds its 1-foot bushy mounds are covered with one-half-inch yellow flowers For earliest blooms start these indoors and transplant after damage of frost- has passed.
UMBELS: Umbels are members of the Umbelliferae or parsley family Many are food or herb plants including angelica and lovage Some are common wildflowers such, as Queen Anne's lace They are regarded as attractors of beneficial insects particularly tiny parasitic wasps that have an easy time feeding on the nectar of their shallow flowers The following family members are especially attractive to beneficials:
· Caraway (Carum carvi L ) 2 to 3 feet high provides aromatic seeds for use in breads and pickles. An annual with feathery leaves and fluffy white flower heads it attracts insidious flower bugs spiders small wasps syrphid flies and lacewings You can start indoors or direct seed
· Dill (Anethum graveolens) is an easy-to-grow annual that reseeds itself readily. It likes moderately rich loose soil and full sun. Germination is easy; just sow seeds where you want the plants. They'll get 2 to 3 feet tall then go to seed. Dill attracts ladybugs syrphids small wasps and spiders.
· Sweet fennel (Foeniculuum vulgave) is an herb, grown for its licorice-flavored seeds and leaves. (Florence fennel is very similar but is grown for its edible stalks and bulb ) It can grow 3 feet high and in mild climates may behave like a perennial Start indoors or direct seed in early spring in moderately fertile soil with adequate calcium and much sun After germination (about two weeks) allow to dry out between waterings. Fennel attracts svrphids spiders and ladybugs (At the New Alchemy Institute in Massachusetts it also attracted 48 species of parasitic wasps.)
MISCELLANEOUS: A wide variety of other plants have interesting relationships with' beneficials Among them:
· Buckwheat (Fagopyrum esculentum) attracts flies ladybugs and syrphids plus pollinating bees It's also an effective soil-builder that adds organic matter when turned in and a good weed controller. Its small attractive white flowers appear in a few weeks and mature seeds three to four weeks later
Buckwheat self-seeds readily. If you don't mow it after full flower it may take over. But that same mowing might harm beneficials in their nvmph, stage when they can't fly away. (For example minute pirate bugs need 20 days to produce a new generation ) The best solution might be to have a permanent buckwheat patch near the garden-- instead of in it.
· Spearmint (Mentha spicata), which makes a refreshing tea and flavoring, attracts various flies and spiders. This 3-foot plant with pretty spikes of purple flowers also has a tendency to take over and should be planted in a container or given lots of space. Transplant (for truer flavors) or start from seed.
· Many kinds of legumes such as crimson clover white clover or vetch can also help you attract beneficials. They provide alternate prey good shelter and moisture and they're absolute champions at adding nitrogen to the soil.
(Note: While attractive LEMON GEM marigold and CUT AND COME AGAIN zinnia harbored fewer beneficials than other composites or the umbels. They were tested because they are so extensively grown.)
In addition to nectar and pollen, beneficials insects also need moisture shelter from wind and rain alternate prey to get them through the lean times anti places to spend the winter. Usually the more diverse and varied habitat will better supply these needs.
First evaluate what you already have. If you grow in containers consider adding a few pots of spearmint or dill If you have a big lawn consider some long strips of fennel caraway or buckwheat near your garden. You can create a border with perennial anthemis and tansy.
Insects are attracted to the shelter of windbreaks and hedgerows and these can also serve to liven up an otherwise dull landscape. A thick stand of cosmos also makes a nice privacy fence A small water garden will supply insects with moisture-- as will an attractive shallow dish filled with pebbles and water.
If vou are partial to flowers. be sure you are planting ones that beneficials like too. Many flowers have been bred for showyness-- size petals and color--and may have lost the nectar and pollen characteristics that make them attractive to insects. Perhaps this is why insects seem to prefer wildflowers and herbs--no one's developed their appearance at the expense of their natural functions
To ensure a full season of beneficial-friendly flowers start with early bloomers such as buckwheat and make succession plantings of dill. Sow cosmos and marigold now for midsummer blooms. Start growing tansy and anthemis for a long season of flowers year after year.
Of course there are some rough edges to be smoothed out. "Tarnished plant bugs seed-feeding bugs that can deform many kinds of fruits and vegetables also like pollen and nectar" So if you think a beneficial planting might be attracting too many insect pests, try another plant.
Remember as with all aspects of organic gardening the goal in using beneficials is not complete eradication of pest populations but control You can achieve a natural balance between pests and predators by creating a habitat that's both useful and ornamental.
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