Chemicals Not the Sole Pest Control

Question: I’m a new home gardener trying to maintain a pest-free environment to the extent possible for my plants and shrubs. Besides chemical applications, what recommendations can you make to help me achieve this objective?

J.B., ORANGE

Answer: The notion of pest control through pest eradication has largely been replaced in recent years by a multi-pronged ecological approach called integrated pest management (IPM).

This pest-management approach is recommended by the University of California Cooperative Extension and is the basis for guidance given to home gardeners by UC Master Gardeners.

IPM is a strategy to prevent and suppress pest problems with minimum adverse effects on human

health, the environment and nontarget organisms.

Chemical controls are but one element of the IPM strategy and are not considered the first line of defense.

IPM’s essential components include prevention, identification of pests and symptoms caused by pests, regular surveying, guidelines for when one should take action and methods to manage pests.

Prevention is the single most important element of IPM. Many common insect and disease problems are caused by overwatering, underwatering or excess fertilizing. Similarly, poor plant choice and incorrect planting may cause or exacerbate problems.

To compound matters, gardeners may attribute such preventable problems to diseases or pests, which may lead to unnecessary and potentially harmful applications of pesticides.

Pest and symptom identification is essential for proper treatment of plant symptoms. This is a challenge for even the most experienced and knowledgeable home gardener, because similar symptoms may have different causes.

Good resources to assist with identification are “Pests of the Garden and Small Farm” (Publication 3332), “Pests of Landscape Trees and Shrubs” (Publication 3359) and the Pest Notes series published by the University of California, Division of Agriculture and Natural Resources.

For information on how to obtain these items, contact the UC Master Gardeners.

Also keep in mind that some pest problems can only be identified reliably by experienced professionals such as certified nursery staff or advisors from the Cooperative Extension or Department of Agriculture.

Regular surveying for pests involves systematic inspection by the home gardener.

John Kabashima, Cooperative Extension horticultural advisor for Orange County, illustrates the importance of inspection to Master Gardener classes with the maxim: “A good farmer walks his field daily.”

Plant damage may be minimized through regular inspection of the garden.

Without regular monitoring, problems may not be detected until they have become so advanced that the only management options are either pesticide applications or removal of the plant.

For agricultural crops, the threshold when one should take action is based on economic considerations. In the home garden, however, more often than not, the criteria are aesthetic and subjective.

Gall-forming insects may cause no real harm to a plant, but the results may offend some gardeners. IPM practitioners recognize that a totally pest-free garden is neither possible nor desirable.

As a practical matter, minor damage in the garden is inevitable, but this doesn’t necessarily spell trouble and require intervention.

Management methods of pest control are often most effective when combined.

Using certain landscape designs and resistant plant species can minimize pest problems.

And proper plant care--correct planting, irrigation, fertilization and pruning--is an important component of IPM.

Mechanical methods of pest control can be effective.

For example, hand-picking snails or using copper bands to deter them, controlling weeds with mulch and pruning out diseased foliage all are good practices.

Altering temperature, light and humidity are ways to indirectly control pests. Some leaf diseases are controlled by thinning the plant canopy to increase air circulation, and applying white paint to trunks of certain young trees can reduce light exposure and prevent sunscald.

Beneficial organisms can help control unwanted ones. This management method is most commonly associated with pest and mite control (using parasitic wasps and lady beetles, for example), but it also be used under certain circumstances against weeds, snails, nematodes and plant diseases.

Chemical control continues to have a role in IPM in the gardener’s battle against pest problems. Recognize that all pesticides are toxic and require great care in their application. If you use an incorrect pesticide, the wrong application rate or improper application methods, more harm than good will result.

The home gardener should always consider the other management methods before using a pesticide. Pesticides can quickly obtain temporary control of certain pest problems when applied correctly, but other practices will often provide more long-lasting control.

Question: I’ve been told that shell ginger would be a good addition to the part of my garden that has tropical and subtropical plants. What can you tell me about this plant and its cultural requirements?

S.W., San Clemente

Answer: Shell ginger (Alpinia zerumbet) is a member of the Zingiberaceae (ginger) family and is native to tropical Asia and Polynesia.

It also has been naturalized in Brazil and some regions of central and south Florida. It is an exotic plant that should be a nice complement to your other tropical plants.

Shell ginger is a striking perennial with lance-shaped, dark green leaves that are 2 feet long and 5 to 6 inches across.

The foliage is long-lasting and often used in floral arrangements. After being established for two years or more, the plant puts out gracefully arching sprays of unusual delicate flowers in late summer.

The flowers resemble strands of pink-tipped white seashells that, when open, appear to contain tiny orchids with yellow and orange markings.

Like the leaves, these flowers are also a favorite of florists.

Shell ginger is a vigorous plant that will rapidly grow 8 to 9 feet high and 3 to 4 feet across. It is evergreen in Southern California regions influenced by the ocean climate (Sunset zones 22-24) and will tolerate light frost.

Elsewhere, freezing temperatures may damage the plant or cause dieback, but it will resume growth in the spring.

Unfortunately, because the plant only flowers on old growth, its flowers will rarely be seen in these colder areas.

There is another shell ginger cultivar, Alpinia zerumbet ‘variegata,’ which has the same blooms as the green-leafed species, but has leaves that are strikingly variegated with irregular stripes of green and yellow.

The plant’s habit is upright and the plant does not require staking as do some members of the Zingiberaceae family.

Variegated shell ginger is somewhat smaller than the non-variegated species, typically reaching a height of 4 to 5 feet, and is not as aggressive a grower.

A dwarf cultivar, Alpinia zerumbet ‘variegata dwarf,’ grows only to about a foot high but has the same yellow and green variegated foliage and white seashell blooms as the variegated cultivar. It makes a good houseplant in Southern California.

There is also a cultivar, ‘variegata Chinese beauty’ that has light- and dark-green marbled foliage and grows to about 8 feet. Shell ginger will tolerate exposure from light shade to full sun, but the ideal is partial shade.

Moisture Helps Fight Afternoon Sunlight

Direct afternoon sunlight can easily brown the tips and edges of the leaves unless the plant has adequate moisture. It should also be placed in a wind-free location.

Shell ginger requires good fertile soil that is rich in organic matter.

Clay soils must be amended with compost to make a suitable medium.

The plant prefers a slightly acidic soil with a pH of 5-7. It also prefers constant, even moisture in the soil--but not oversaturation--and conditions of high humidity.

Shell ginger should be given regular applications of a balanced fertilizer, such as palm fertilizer, every two to four weeks during the active growing season.

When it has finished flowering, it may be watered less, but the soil should never dry out completely.

Shell ginger grows from a root system of thick, fleshy rhizomes that look similar to the ginger root found in markets.

It may be purchased as a potted plant or can sometimes be found as a rhizome.

Because it is such a vigorous grower, the shell ginger’s clump needs to be divided every two years.

Though it can be propagated by seed, it is best to grow new plants through division or plant rhizomes because the shell ginger grows rapidly.

For rhizomes, position the “eyes” or new growing shoots in an upright position, then cover the rhizome with about an inch of soil, preferably sandy loam that has been improved with leaf mold or well-composted manure.

Shell ginger can be planted as either a single specimen or in a large grouping in the garden. Because it is less aggressive than the non-variegated species, the variegated shell ginger is also suitable as a container plant on a shaded patio or in a brightly-lit area indoors.

The variegated shell ginger is sometimes incorrectly identified in some nurseries or garden catalogs as Alpinia nutans, which is a very different-looking plant.

Many plants in the ginger family are known for their medicinal or culinary uses. Shell ginger is not commonly used for those purposes, but the leaves and roots do contain the same chemicals (kavain and dehydrokavain) found in the kava plant that herbalists use for its relaxing properties.

Keep in mind, however that there has been a low level of toxicity associated with eating the plant parts of shell ginger, and having contact with the sap may lead to minor skin and eye irritation.

Written by University of California Master Gardener Edward A. Shaw of Laguna Beach.

Have a problem in your yard? University of California Cooperative Extension (UCCE) Master Gardeners are here to help. These trained and certified horticultural volunteers are dedicated to extending research-based, scientifically accurate information to the public about home horticulture and pest management. They are involved with a variety of outreach programs, including the UCCE Master Garden hotline, which provides answers to specific questions. You can reach the hotline at (714) 708-1646 or e-mail ucmastergardeners

@yahoo.com. Calls and e-mail are picked up daily and are generally returned within two to three days. Please include your name and city of residence.