Sometimes a barrier isn't the answer. You wouldn't want to drape a cover over a rose bush or shimmy up an apple tree with a bolt of cheesecloth. There are situations when you need to spray a pesticide. Many plants look or produce much better if kept on a regular spray schedule. Fruit trees in particular yield more fruit if maintained this way. This should be an important consideration in the decision to plant home fruit trees.
What you spray depends on several factors, one of which is your budget. Chemical pesticides are expensive in more ways than one. Research has determined toxins, once commonly used in the garden, can cause a range of ills from birth defects to cancers. Accidental ingestion by pets and children occurs every year, with tragic results. Toxins also wipe out beneficial insects, such as bees and ladybugs. And misapplication of chemical pesticides often results in plant damage.
As with the misuse of chemical fertilizers, the biggest problem home gardeners have with pesticides is over-application. Always follow label instructions to the letter. These are not mere recommendations, they are lawit is illegal to misuse pesticides.
Each product lists what insects it is effective against and on which plants it is safe to use. A general pesticide with a wide range of applications, such as Orthene or diazinon, will handle most problems of home gardeners.
Organic pesticides, such as botanically derived rotenone, pyre-thrum, ryania, and sabadilla are good substitutes for environmentally concerned gardeners. They pose less threat of environmental damage because they break down quickly, and will not leave any long-term residues. Other examples of non-toxic pesticides are horticultural oil sprays that coat and suffocate small bugs such as scale, and diatomaceous earth, which kills bugs at or beneath ground level when worked into the soil. Many organic pesticides, unfortunately, kill indiscriminately, wiping out pests and beneficial organisms alike.
Some of the most promising pest-control products are ones that cause diseasegenerating pest-specific disease organisms that spring to life like sea monkeys when mixed with water. They only harm the bug for which they are intended. Some examples include several forms of the bacteria Bacillus thuringiensis (Bt), marketed under various brand names and effective at battling caterpillars and Colorado potato beetles; Nosema locustae, sold as Grasshopper Attack, which is a grasshopper disease that prevents successive generations; and Bacillus popilliae, or milky spore disease, that wipes out Japanese beetles.
One of the best methods to prevent insect damage is physically preventing bugs from touching plants. Several methods work well depending on the plant and the insect. All methods mentioned are very effective and reasonably inexpensive when done properly.
Many diseases and soilborne insects that attack plants remain in the soil even after you harvest the crop. They wait there to reinfest susceptible plants. If you plant the same crop or a closely related one in that site a disease or insect will probably attack the new planting. Prevent this needless loss by rotating your crops each year. The practice costs nothing and could save a lot. 
It is the nature of disease organisms and pests to take the easiest route. What could be easier than moving down a row of your favorite host plants and attacking one after the other of them? Organic gardeners have known for generations a way to confound many pests, especially those that prefer one particular crop over others, and it doesn't cost a cent. 
The first line of defense is to kick the competition when it's down. Don't allow weeds to get a foothold. Not only are they unsightly, weeds are real enemies of any gardener. They rob the soil of water and nutrients meant for cultivated plants. Many harbor diseases or serve as alternate hosts for pests. If allowed to grow, they may shade plants from sunlight, block air circulation around foliage, or crowd out crops entirely. 
So much of the information already discussed contributes to your plants' overall health. The best site, proper planting, and transplanting, using resistant varieties, adequate watering, drainage, and nutritional support all help keep plants in optimum condition. Healthy plants have an edge. They are less susceptible to physical stress, attack by disease, or infestation of pests. In fact, studies show insects recognize and prefer ailing plants. 
Many gardeners buy compost starters to get a pile fired up. These are basically high-nitrogen products that may or may not work, depending on what else is in your pile. Fresh green weeds, with a little soil clinging to their roots, or a shovelful of soil or compost, tossed at intervals into the pile will suffice. But for a great, cheap pile activator, try alfalfa. Toss in handfuls from bales (old or rained-on bales are the cheapest) or use an alfalfa meal product. Horse feed, rabbit food pellets, even some brands of cat litter, are almost pure alfalfa meal. 
