How to Grow Garden Vegetables Without Pesticides
By Janet Hartin, M.S.

Contrary to what insecticide companies insist upon with their marketing and publicity, you don’t have to choose between having your home-grown vegetables and fruits devoured by insects versus applying commercial pesticides. Today, home gardeners have a wide choice of non-chemical measures to prevent and control pests, along with a range of  environmentally-friendly practices that further encourage healthy gardens.  
The first step is to select plants well adapted to your climate and to nurture them by applying the right amount of water and organic fertilizer, along with keeping the garden weed-free by mulching and hand-picking newly germinating weeds. The next step is to carefully diagnose any problems that develop early and to use appropriate control measures before the problem spreads.

Integrated Pest Management
Preventing and controlling pest problems in an environmentally-friendly way is known as Integrated Pest Management (IPM). IPM relies on a variety of strategies to prevent major pest outbreaks by choosing recommended control methods that provide long-term pest prevention and suppression with minimum impact on the environment and human health.

One strategy is to regularly inspect your garden plants for signs of insect activity using a 10 – 15x hand lens. Remember that not every species of insect that you find during your detective work will be a ‘bad guy’ needing to be eliminated. There are a wide variety of beneficial insects that are essential for controlling unwanted pests. Unwarranted application of an insecticide to control what you assume is a pest can wipe out these beneficial garden friends and lead to weakened plants unable to compete with opportunistic insects and diseases. Also, repeated application of pesticides can result in the development of pesticide-resistant strains of insects and diseases.  

Common Problems

Poor plant growth can be caused by too much or too little water, inadequate sunlight, unfavorable temperatures, root damage, too much or too little nitrogen, or other factors. For instance, planting sun-loving crops in the shade can result in overly tall and lanky plants, which often develop yellow leaves (chlorosis) that may be mistaken for a nutrient disorder.

Often in cool spring weather powdery mildew will develop on your plants. This usually does not cause serious damage and will dissipate once the weather is on the plant’s side when warmer temperatures prevail. Doing nothing is actually best in this case! Instead of wasting time and money controlling a ‘non-problem’ take a brisk walk, hit the gym, or work in another part of your garden.

Good Detective Work
Sometimes insect problems are noticed after a homeowner returns from vacation; chomped Jacaranda leaves are not pretty, but be sure to identify the culprit before deciding if anything should be done. It could be that mature caterpillars did a ‘hit-and-run’ and are long since gone. In time, the damage will disappear as new foliage develops.

Since insects have varying stages and life-cycles, good detective work requires identifying which stage resulted in the problem and when and if control is warranted. For example, the only recommended time to control the juniper twig girdler in Southern California is in early spring since this pest tunnels under the tree bark the rest of the year.  

Pest Resistant Plants

One of the first lines of defense against offending pests is a good offense! Select pest-resistant ornamental and garden plants whenever possible. While this doesn’t guarantee that your fruit or landscape trees will escape all pests all the time, it does help ensure that damage will be much less.

What makes certain plants pest resistant? Some have chemical or physical properties that discourage damage, while many others can simply function and grow adequately even under attack. Remember that it is always important to select plants that will grow well in your climate. Often even insect and disease resistant plants die from other causes such as a climate that is too cold or too hot (check the Sunset planting zones for your exact area.) Remember that microclimates – those smaller climates around your home  – also impact how well your plants do, based on shade, soil compaction, pH, nutrition, drainage, and the like.

Proper Sanitation

Another way to keep your garden and landscape plants healthy is through good sanitation practices. Remove diseased plants to reduce the chance of the organism in question spreading to healthy plants. Compost or recycle weeds to reduce competition for water and to eliminate food and shelter for insect pests such as aphids and spider mites.

Other Healthy Garden Practices
Other garden practices that decrease the chance of insect and disease damage include crop rotation (avoiding planting the same family of vegetables in the same location year after year) and planting and harvesting your produce at recommended times based on crop preferences. For instance, planting warm-season vegetables after soil has had a chance to warm in late spring can reduce the chance of maggot damage and damping-off disease. Many gardeners place "hot caps" (milk cartons, paper sacks, etc.) around plants during early spring to increase heat and to protect young plants from wind and insects. Other practices include placing paper collars around stems to prevent cutworm damage; covering small fruit trees, berries, and tomatoes with mesh to prevent damage from large insects and birds; and, adding sticky barriers to tree trunks to reduce and prevent damage from crawling insects.

Don’t be afraid to hand-remove insects and insect egg masses. This practice works especially well for pests such as beetles, hornworms, and squash bugs. And, never underestimate the effectiveness of shooting a fine stream of water from a hose to dislodge spider mites and other insects from foliage and stems.       

What about trapping? Earwigs can be removed by placing rolled-up newspapers in your garden while pillbugs and slugs can be trapped under boards.  You can attract and kill tomato hornworms with a compote made of beer or fruit juice, and trap grasshoppers and certain beetles in a container filled halfway with a 10 percent solution of molasses and water.

Don't Let "Perfect" Fool You
Many gardeners are used to perfect ‘model-like’ produce like shiny apples and perfectly round red tomatoes with nary a blemish. While this image has been perpetrated in the media and at local grocery and produce stores for decades as the pathway to health and beauty, the truth of the matter is that many of these blemish-free fruits look that way due to the application of pesticides. It is much healthier to steer clear of pesticides whenever possible and accept a less than perfect looking homegrown apricot, strawberry, or cantaloupe that is not only packed-full of vitamins, but tastier than older store-purchased ‘perfect’ fruit.

When I was a graduate student years ago in another state, we cut up fresh local (yet small and somewhat misshapen) applies and shipped in applies from another state and offered them to visitors at the local arboretum, asking them to rank their flavor and overall quality. As expected, the local apples won hands-down when it came to taste, but afterward when the same visitors asked to buy the fresh locally-grown apples and saw what they looked like whole, often they would not purchase them! Some even bought the shipped-in apples that they had just rated far less flavorful!   Because this was two decades ago and times have changed, I hope that if this experiment were repeated today, the results would be far different!   The moral of this story is that a fundamental component of IPM is that a small amount of pest damage should be tolerated in favor of health.

Happy Gardening! If we all incorporate just a few of these techniques, we can reduce garden pests and grow bumper crops of nutritious and delicious vegetables and fruits while leaving a gentler environmental footprint for our children and grandchildren.


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