Rotations are the first and best way to prevent pest & disease problems. The next best option is hand removal of old plant residue if working in a small garden. Organic growers tend to use organic insecticides as a last resort.

Insecticidal soaps (not household) can control a wide range of plant destructive insects, especially aphids.

Pest Control
Pests are animals of various kinds that reduce the amount of produce available for harvest. The golden rule of pest control in the garden is: "if in doubt, do nothing".

The first and best defence for plants against predators, parasites and diseases is general health and resistance. Many insects do very little damage directly. The first step is to recognize that 99% of insects are either harmless or predators of those we don't want. You can encourage predators by increasing the ecological diversity of your garden.

Birds are effective predators of insects and grubs. Plant shrubs where they will reproduce and increase their numbers.

In the home garden, mixed plantings of different types of vegetables and herbs can confuse the pests' detection systems so much as to almost eliminate loss.

Disease Control
The main damage that insects do is the spreading of viruses. Natural immunity is your plants' only defence. A weak or unhealthy plant is more likely to suffer disease. A strong, healthy plant can defend itself. Your first line of defence against pests and diseases is to choose plants with the most genetic potential for self-defence.

Always plant more seed than you need; select the strongest and cull the weakest. Do this at the seedling stage and again when planting out into your garden beds.

No genetic inheritance will reach its full potential without the right nutrition. Well cared for plants can fend off disease themselves. Don't overindulge with water-soluble fertilizers. If your fertilizer is very Nitrogen-rich, plants can put on lots of new growth and appear to be doing well. However, without the other nutrients necessary to construct healthy new cells, this new growth can be made up of thin-walled, weak cells that are excessively vulnerable to pests (particularly sap-suckers like aphids) and diseases (particularly fungus diseases).

Malnourished plants succumb to diseases that healthy plants hardly notice.
Micronutrients probably perform something like the same function in a plant's diet that vitamins do in a human diet. A great remedy for a number of plant ailments, especially aphids, is a good dose of seaweed brew.
It doesn't kill the pest, but (probably because it is so rich in micronutrients) it increases resistance to the point where the pest is irrelevant.


Tips

• Keep plants healthy.
• Rotate vegetable plants and sites.
• Space vegetables further apart to allow more air flow.
• Plant to take advantage of the prevailing winds so air flow is increased down the row.
• Don't go into the garden when plants are still wet.

• Sanitation is important. Remove and destroy all parts of dead plants. They are a source of disease. Do it immediately after they are no longer useful! When thinning, remove thinned plants immediately.

• Don't harvest vegetables when plants are wet.
• Avoid overhead watering. Drip irrigation can efficiently deliver water and keep foliage dry.