I.Importance of natural method of pest control
The problem with broad range conventional pesticides is that they not only kill the bad bugs, but they rub out the good bugs, too. A garden without natural predators means a world of insects gone wild. There's nothing left to keep pest levels in check. In fact, chemicals can mean double trouble because although you wipe out the first wave of pests, the second wave which is not the usual pest, but another insect moving into the area can cause even greater losses than the insects you were trying to get rid of in the first place. Another reason to go natural and use beneficials, is that a greater number of insects are now showing resistance to chemical pesticides. For example, in a controlled laboratory experiment, fruit flies were exposed to DDT a banned pesticide. The research found that not only did the pesticide not kill them, but the fruit flies had developed a way to metabolize it! That is, the "super" flies could use the pesticide as food. Pesticide resistance is not an isolated problem. About 500 insect species now show resistance to conventional pesticides. You won't have that problem with beneficial insects. No insects have shown immunity to being eaten. They can run, but they can't hide from beneficial insects.
II.Natural methods for controlling pest
Control of garden pests can be achieved through natural methods, including crop rotation, homemade spray repellants, physical method, Introduction of prey species, interplanting which reduces the spread of pests and disease that agribusiness monocropping accentuates and through the use of companion planting of plants which may demonstrate pest-repellant characteristics. A.Crop Rotation
Crop rotation is the practice of growing a series of dissimilar types of crops in the same space in sequential seasons to avoid the buildup of pathogens and pests that often occurs when one species is continuously cropped. Crop rotation also seeks to balance the fertility demands of various crops to avoid excessive depletion of soil n-utrients. A traditional component of crop rotation is the replenishment of nitrogen through the use of green manure in sequence with cereals and other crops. It is one component of polyculture. Crop rotation can also improve soil structure and fertility by alternating deep-rooted and shallow-rooted plants. Crop rotation is also used to control pests and diseases that can become established in the soil over time. Plants within the same taxonomic family tend to have similar pests and pathogens. By regularly changing the planting location, the pest cycles can be broken or limited. For example, root-knot nematode is a serious problem for some plants in warm climates and sandy soils, where it slowly builds up to high levels in the soil, and can severely damage plant productivity by cutting off circulation from the plant roots. Growing a crop that is not a host for root-knot nematode for one season greatly reduces the level of the nematode in the soil, thus making it possible to grow a susceptible crop the following season without needing soil fumigation. B.Homemade Spray Repellants
Pathogen Spray collect several dozen insects and placing them in a blender with a little water (use rain water rather than tap water to avoid the chlorine), sieve the resultant mixture and dilute it with several times the amount of water, then spray it on the pests. Hot Peppers: Boil 2 or 3 very hot peppers, half an onion and one clove garlic in water. Steep for 5-10 hours and drain through cloth. Spray on foliage. Avoid contact with eyes. Soap: The least toxic chemical for many gardeners is a soap mixture. Spraying plants with soap water will control aphids, mealy bugs, thrips, red spider mites, and lice. Mix two tablespoons of liquid soap per one quart water. Spray on plants. Disadvantage: Using pure soap, additives or detergents may damage plants. Effects: Insecticidal soap works only on...