Prevention is the easiest way to discourage pests from coming in the first place. A healthy garden is the best defense and here are some tips:
Healthy organic soil. Natural composting, mulching and top-dressing your soil with compost are the best way to develop strong plants.
Pull out weak plants. The weak plants may already be infected. Pull and dispose of them away from the garden.
Seaweed mulch or spray. Seaweed fertilizer in mulch or spray will enhance growth and give plants strength. Seaweed mulch also repels slugs.
Interplant and rotate crops. When plantings are mixed, pests are less likely to spread throughout. Rotating crops each year is a common method to avoid re-infestation of pests.
Keep foliage dry. Water early in the day so foliage will be dry for most of the day. Wet foliage encourages insect and fungal damage.
Disinfect. To reduce the spread of invading insects, clean your tools after working with infested plants before moving on to other areas of your garden.
Minimize habitat. Be sure to clear your garden area of debris and weeds as this is a breeding place for insects.