Weed/Disease Control

Pesticides are used extensively to treat plant diseases and remove unwanted plants, or "weeds", from lawns and gardens. The list of active ingredients commonly used is enormous, and many of them are so toxic that the EPA, never the first to condemn, has restricted or banned their use. Hundreds of compounds in different combinations are used and new ones are continually produced to combat ever-more pesticide resistant strains of plants & animals. These pesticides have polluted our soil, our waterways, our very bodies.

Scores of diseases leading to permanent damage or even death have been attributed to pesticide exposure. It is easy to use these "silver bullets" and they generally kill whatever pest you're trying to kill. Unfortunately, pesticides don't know when to stop killing. They affect our pets, ourselves, and our children where they can cause serious problems with development. Once applied, they seep into the soil, completely altering the balance of microorganisms found there which everything else in the area rely upon for a healthy ecosystem. They contaminate surface and ground water, flowing into our waterways where they are toxic to aquatic life and everything else that drinks from those waterways.

That said, there are ways to deal with weeds and diseases both that don't required the use of harmful pesticides.

WEEDS - traditionally treated with herbicides (see above)

1. Healthy lawns out-compete weeds! It's true. When your lawn is healthy, it crowds out any weeds that may try and invade. See the post on lawn care for more information on how this is managed. Key elements to watch out for are pH and nitrogen levels.

2. Bare ground attracts weeds. Fill all areas with good ground cover plants or mulches so that weeds don't have any room to grow. Good ground cover mulches include sawdust, bark, nutshells, or straw & composted vegetation (NOT WEEDS!) for your gardens.

3. Place weed mats underneath mulches. There are many varieties available, so make sure that you pick one that is water permeable. No black plastic! For a do-it-yourself version use 10-15 overlapping layers of newspaper or cardboard covered with 3-4 inches of compost or mulch.

4. Make sure manure, compost, mulches, etc… are weed free before purchasing. Many weeds are imported this way and can quickly take over your new planting areas.

5. Deep tilling can bring old weed seeds to the surface where they will sprout. Be sure to use or "build" fresh topsoil. To create your own topsoil, cut all weeds & grass in the area, lay down a weed mat, top with grass clippings, dried leaves, compost & manure. Set up your topsoil in the fall for a spring planting so that it has time to settle.

6. Before planting in new soil, water the area well and wait for a week to see if any weeds sprout. Rake them up and repeat until no more weeds come up. Your soil is now weed-free and ready for planting.

7. Pull weeds by hand and make sure you get the root. There are even special tools out there designed to help you pull the entire root system of perennials such as dandelions.

8. Take the time to identify your weed and learn about its life cycle. Many plants have a certain time of year that they will appear in and a time period in which they are most vulnerable. For example, perennial weeds should be pulled within 4-6 weeks after sprouting to prevent the formation of persistent parts which will cause the weed to keep coming back.

9. Repeated mowing can help to weaken perennial weeds, making it harder for them to come back, especially if they were already well-established.

10. Boiling water applied directly to weeds in your driveway, sidewalk, etc... will kill many varieties of weeds, especially if you catch them when they are young and tender.

11. Fire applied VERY CAREFULLY to weeds in areas completely surrounded by non-flammable materials (i.e. driveways, sidewalks, patios) will often kill the weed. Garden-use "blow torches" can be purchased at a number or garden supply stores but should always be used with the utmost care.

12. Finally, there are a number of natural pesticides available such as BurnOut Weed & Grass Killer that are based on vinegar and plant oils. They will kill or severely weaken the plants they are applied to without severely affecting soil health and are completely non-toxic, though they may still make you sick if ingested.

DISEASE - traditionally treated with fungicides

Most plant diseases are the result of a fungal infection. The most common fungicides (Triforine, Chlorothalonil, Daconil 2787) have been shown to cause skin or eye irritation, allergic reactions, bronchial irritation, are toxic to aquatic life, and one common ingredient, chlorothalonil, has been shown to be carcinogenic in lab mice & rats.

1. The first thing to remember about plant disease: healthy plants tend to stay healthy! If you support healthy plants, they will be much less susceptible to disease.

2. Keep a balanced, diverse population of microorganisms in the soil to support healthy plant-life. This can be done by applying soil inoculants (available from organic garden supply stores) and mixing lots of rich organic material into the soil.

3. Avoid overhead watering. Use drip lines, or other ground-level irrigation methods.

4. Prune regularly to allow plenty of air circulation through the plant's leaves.

5. Use mulches and prune lower branches to keep infected soil from splashing up onto the leaves where it can cause damage.

6. Choose native plants naturally resistant to your area's local diseases.

7. If your plant still begins to look unhealthy, make sure the culprit is disease and not nutrient imbalance, drought, over-watering, sunscald or too much shade.

8. Always identify your disease accurately before beginning treatment. Learn what you can about the particulars of the disease as each one will have different treatment options. Here in Eureka you can call UC Agriculture & Natural Resources Cooperative Extension at 445-7351 for help identifying plant diseases. There may be similar agencies in other areas. Otherwise, most local nurseries can help you identify the disease if you bring in a small cutting.

9. Once you have identified a disease and looked into treatment options, choose natural fungicides like copper soap which are available at organic garden supply stores.


Whether dealing with weeds or disease, prevention is the best way to handle the situation. A little extra care in growing and maintaining your flora will often eliminate the need for harsher measures later.