For example, growing potatoes in a row is almost an open invitation to the Colorado potato beetle to come to dinner, as when any vegetable is planted in dense quantities, the smell it gives off (undetectable to humans, but very obvious to its primary insect pests) is concentrated, attracting its enemies. But if you plant your potatoes here and there among other vegetables or in the flower garden, its beetle enemies will have a hard time finding them.
It’s the same thing for carrot fly, tomato hornworm, even vine weevil. Mixing things up at planting time results in fewer insect attacks.
That’s why is it best to avoid “monocultures” (cultivation of a single vegetable over a large area). With a diversified, mixed vegetable garden, your plants will suffer from far fewer insect pests.
Since I gave the Colorado potato beetle as my main example and it is indeed one of the more difficult insects to control, here are a few other suggestions on how to prevent and treat them.