You can reduce the plant diseases and insects that attack your vegetable garden by practicing crop rotation. Crop rotation simply involves not planting crops of the same family in the same section of the garden year after year.
Plants that are related to each other tend to be prone to the same diseases and insect pests. For example, squash borers will attack not only squash vines but also pumpkins (both members of the cucurbit family). The squash borer larvae over winter in the soil in a cocoon. But if they wake up the next summer and the squash vines are now at the other end of the garden, the borers will have more difficulty finding the vines.
In the section of the garden where last year's tomatoes or eggplants (members of the nightshade family) were growing, plant some members of the cabbage family, such as broccoli or cauliflower. These cruciferous crops have the ability to clean the soil of diseases that attack members of the nightshade family - potatoes, tomatoes and eggplant.
Rotating crops is not complicated and you will have better plant health.
Barbara Null, Smith County Master Gardener
Texas AgriLife Extension Service