Controlling Common Garden Pests... Organically! Part 1: Prevention

Common Garden Pests Part 1: Prevention!

It's nearly July. Summer is here, the days stretch out, our gardens are practically growing before our eyes, the sunshine is abundant, and so (it turns out) are the pests!

The arrival of these perfect growing conditions always seem to coincide with the arrival of those uninvited companions in our gardens who insist on having the very first tastes of anything we plant. And who could blame them? They often have impeccable taste. Every garden has them, in different numbers and combinations, and so it becomes not a question of if, but who, and then what to do about them.

As organic gardeners, the answer to this question should start long before the pests ever arrive! The most vibrant and healthy edible gardens are designed and planted with natural controls against would be enemies. This post will discuss several things you can do in your garden to stop pest problems before they even begin! Vegetable rotation, encouraging beneficial insects, and thoughtful crop selection are three extremely effective ways to prevent unwanted garden pests.


Crop Rotation

Crop rotation, or vegetable rotation, is the practice of planting different families of vegetables in different locations over time. The benefits of this practice extend far beyond preventing pests, also suppressing plant disease and improving soil fertility over time.

Keep records of the locations of vegetable plantings so you can create rotations in seasons to come.

Keep records of the locations of vegetable plantings so you can create rotations in seasons to come.

Most garden pests, like humans, have strong preferences when it comes to their diet and tend to predate on the same vegetables year in and year out. By avoiding planting the same vegetables in the same place each year, populations of pests that enjoyed your arugula in year one will be very unhappy to find tomatoes growing in year two. These constant changes in their environment are confusing and frustrating to pests, and lead to less pest pressure overall!


Planting for Beneficial Insects

One of the most effective ways to control pest populations in your edible garden is to create habitat for their natural predators! In general, annual vegetables are not great habitat for many of the insects that prey on garden pests, so it is only through thoughtful planning and planting of other perennials and flowers that we can create a balanced ecosystem that keeps their populations in check.

Conventional agriculture, which relies so heavily on herbicides and insecticides misses this point entirely. The broad spectrum insecticides kill both pests and beneficial insects. When pest problems do persist on conventional farms, they get out of control easily because of a lack of natural predators.

Every pest has a unique set of natural predators. It can be very difficult to anticipate what pests will afflict your garden, so it is a good practice to plant a diversity of plants and flowers, both perennials and annuals that provide habitat and food (pollen/nectar) for beneficial insects.

Cosmos is an excellent insectary flower attracting Ladybugs, Lacewings, and parasitic wasps which prey on Aphids, Whiteflies, caterpillars, and beetle larvae.

Cosmos is an excellent insectary flower attracting Ladybugs, Lacewings, and parasitic wasps which prey on Aphids, Whiteflies, caterpillars, and beetle larvae.

Some excellent insectary plants for the Willamette Valley include: Cosmos, Coreopsis, Phacelia, Clarkia, Baby Blue Eyes, Clovers, Calendula, Yarrow, and Buckwheat. Inquire at your local nursery about “insectary seed mixes”, special seed mixture designed with your beneficial insects in mind!

An insectary seed mix from Uprising Seeds, a local seed producer. Beautiful, beautiful seeds!

An insectary seed mix from Uprising Seeds, a local seed producer. Beautiful, beautiful seeds!

The Xerces society, based here in Portland, is an incredible local resource that is dedicated to the study, protection, and promotion of invertebrates and beneficial insects.  Check out their resource Farming for pest management”  for good ideas about thoughtful landscape design.

Also look at Renee's Garden Seeds' “Beneficial Insect Guide” for detailed info on specific predator/plant relationships.


Vegetable/Varietal Selection

A final way to curb pest problems is through careful and thoughtful selection of what you plant. Certain vegetables are especially beloved by specific pests, and so in some cases you may decide you are better off not growing certain vegetables.

This is generally an unsatisfactory answer for the most passionate gardeners. Short of cutting vegetables out of your rotations, experiment with different varieties, do your homework, read seed packets, consult with other gardeners, and inquire at a reputable nursery about pest resistance among varieties.


By using the prevention methods discussed above: rotating different plant families each season in your garden, creating habitat for beneficial insect populations, and being thoughtful in selecting the vegetables and varieties you grow, you will create an environment that is naturally resistant to the most common garden pests! The pest challenges that you do face going forward should be much easier to control since you have taken these important steps!

In my next post, I will discuss how to identify and organically control the pests that do find their way into your garden using a variety of different methods including a range of organically certified products as well as other natural and more homespun methods. Until then, enjoy the bounty and lets all encourage summer to settle in for good!