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Controlling insects and diseases

Insect Pests. Do not apply an insecticide unless it is necessary to prevent damage to flowers or shrubs. Most insect pests in the garden will not cause appreciable damage if their predators and parasites are protected by avoiding unnecessary applications of insecticides. However, if there is a pest that usually causes serious damage unless an insecticide is used, apply the insecticide as soon as the infestation appears and begins to increase.

Watch for such insect pests as spider mites, aphids, June beetles and other beetles, lacebugs, and thrips; these are some of the insects most likely to need prompt treatment with insecticides. Do not treat for soil insects unless you find numbers of cutworms, white grubs, or wireworms when preparing the soil for planting.

When using a pesticide, be certain that the pest and the flower or shrub are indicated on the label. Read and follow all directions for use, including precautions, shown on the label. If pesticides are handled, applied, or disposed of improperly, they may be injurious to human beings, animals, and fish as well as to plants, flowers, and beneficial insects. Use pesticides only when needed, and handle them with care.

Diseases. Since annuals only grow in the garden for one season, diseases are not as serious a problem as they are for perennials. Select varieties of plants that are resistant to disease, follow recommended practices for planting and maintaining annuals, and you will avoid most disease problems. However, there are times when weather conditions are highly favorable for diseases. If this happens, determine what disease is affecting the plants, then apply the appropriate pesticide according to label directions.

Damping-off causes seeds to rot and seedlings to collapse and die. The disease is carried in soil and may be present on planting containers and tools. Soil moisture and temperature necessary for germination of seeds are also ideal for development of damping-off. Once the disease appears in a seed flat, it may travel quickly through the flat and kill all seedlings planted there. This can be prevented. Before planting, treat the seed with a fungicide, sterilize the soil, and use sterile containers. Treat the seed by tearing off the corner of the seed packet, and through the hole in the packet, insert about as much fungicide dust as you can pick up on the tip of the small blade of a penknife. Close the hole by folding over the corner of the packet, then shake the seed thoroughly to coat it with the fungicide dust.

Unless you use artificial soilless mixes, sterilize the soil in an oven. Fill a metal tray with moist, but not wet, soil. Hold it at 180º F for 30 minutes. Do not overheat. This will produce an unpleasant smell.

To avoid introducing the damping-off organism on containers, use fiber seed flats or peat pots. These containers are sterile, inexpensive, and easily obtained from garden shops. Fiber flats are light and strong. They cost so little that they can be thrown away after one use. Peat pots can be set out in the garden along with the plants they contain; roots of the plants grow through the walls of the pots. Plants grown in peat pots suffer no setback when they are transplanted to the garden. Larkspur and poppy, which ordinarily do not tolerate transplanting, can be grown in peat pots satisfactorily. If wooden boxes or clay flower pots are used for soil containers, clean them well. Soak clay pots in water and scrub them to remove all the white fertilizer crust from the outside. Sterilize clay pots by swabbing them with a solution of 1 part chlorine bleach to nine parts water. Allow containers to dry thoroughly before filling them with soil. If, despite precautions, damping-off appears in seedlings, discard the containers and soil and start again.