Archive for phytochemical

Residue Problems with Herbicides in Gardening

Residue Problems with Herbicides in Gardening

By George Giltner, MS Biology, Adv. Master Gardener

 

A recent Mercola interview with MIT research scientist, Dr. Stephanie Seneff has raised the awareness of human health problems with glyphosate (Roundup) that has entered the American food supply by genetically modified organisms (GMO’s which include wheat, corn, soybeans, etc.).

 

Everyone has heard the sales pitch of how “biodegradable”, “environmentally friendly”, and “clean and inert” it is for years.  Now biochemical research is painting a different picture that looks more like an evil villain.  Mounting evidence according to Dr. Seneff pictures glyphosate as “the most important factor in the development of multiple chronic diseases and conditions that have become prevalent in Westernized societies”.

 

These chronic diseases are the result of nutritional deficiencies and systemic toxicity caused by glyphosate. Strangely, the mechanism of harm is through intestinal microbes.  Beneficial gut bacteria are preferentially affected (as weeds), causing disruption in microbial functions and lifecycle.  Pathogens flourish and then inflammation causes disease.  For a better description of the mechanisms, please view the hour-long interview: www.articles.mercola.com./sites/articles/archive/2013/06/09/monsanto-roundup-herbicide.aspx.  Note: Some terms are scientific, however concepts are simplified by an interviewer.  Discussions involve biochemical mechanisms related to autism, allergies, gastrointestinal diseases, diabetes, cardiovascular disease, etc.

 

When you do use Roundup at home treat it with respect. Wear PPE, bathe, wash clothes, and do not inhale spray droplets.  Keep the kids away from spray area and don’t let the dog roll in grass sprayed that will be rubbed off by petting at a later time.  Remember that the half life of glyphosate ranges from 1 to 174 days as water and bacterial action are required for degradation.  In ponds the half life is about 2 weeks to 10 weeks.

 

Another herbicide commonly used is “Sledgehammer”, halosulfuron-methyl. For controlling pesky nutgrass this herbicide will work by systemically destroying the nut tuber and stem.  The question always comes up – “Can I use it in my Vegetable Garden?”  The answer is emphatically “No” or “No Way”.  The reason – The EPA states that it can persist at toxic levels to plants for months or years.  Therefore if you have a garden area that was sprayed with this chemical, and it has not produced vegetables for years, it may be due this persistent chemical herbicide.

 

Yet another herbicide, Tordon (picloram) is commonly used to rid property of tallow trees or to destroy regrowth from stumps. The problem with Tordon is that it also persist for a long time, like several years.  Trees in the vicinity of a treated tree may also be killed as the chemical can be easily absorbed by nearby roots.  Broadleaf crops can be damage for up to two years.  Extension recommends use of Roundup for stumps and root sprouts.  Tordon should not be used for backyard usage.

 

These are just three examples of herbicides with residual or human health effects. Before you use any chemical for gardening, do like our county agent says, “Read everything on the herbicide label”.  Also be sure to wear PPE, and above all keep updated on new research and herbicide safety.

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Toxins in Mulch – Allelopathic Phytochemicals

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Toxins in Mulch – Allelopathic Phytochemicals

By George Giltner, MS, Adv. Master Gardener

Select your choice of mulch wisely!  Remember that when leaf, bark, wood, nut stem or root mulch is placed around vegetation, you are essentially placing organic chemicals within the living space of growing plants.  When many of these compounds are not decomposed, they perform their original function as a competition inhibitor or toxin.  Think of plants as competitors in a continuous battle for nutrients, water, sunlight, and space.  “Better living through chemistry” is how they win.

Pliny the Elder, a roman scholar, observed that walnut trees were toxic to other plants.  As history repeats itself, gardeners have experienced the effect of juglone, the chemical allelopathic compound of walnut trees that is responsible for reduced growth or death of surrounding plants.  Juglone is concentrated in the buds, nut hulls, and roots, but it is also present in leaves and other plant parts.

Tomatoes, peppers, and other Solanaceous plants are very susceptible to juglone’s effect as a respiration inhibitor.  The plants will exhibit symptoms as wilting, yellowing, and eventual death.  Plants that are sensitive to juglone include apple, azalea, blackberry, blueberry, chrysanthemum, pine, potato, rhododendron, thyme, and many others.  However plants that are resistant to juglone include beets, carrots, corn, snap beans, melons, onions, etc.  Yet these plants may exhibit some degree of toxicity.

Trees related to walnuts, such as hickories, pecans, and English walnuts also produce juglone, but in smaller quantities.  These trees are responsible for pollen allergies in humans and horses.  Horses may even be affected by walnut wood chips when it is used as a bedding material.

Aerobic composting of leaves is effective in degrading juglone and other allelochemicals.  Moisture, mixing, temperature, and microbial action are factors that determine the degree of decomposition to non-toxic levels which can occur in as little as three weeks.  However, it would be safer to allow 6 months of complete decomposition time before using this compost.  Also maintain high organic matter around plants to produce microbial populations that can metabolize toxins.  Twigs, chips, and sawdust from walnut trees are harder to digest, therefore it is best to avoid using them for mulch, compost, or bedding material.

Another allelotoxin is ailanthone from the ‘Tree-Of-Heaven’, Ailanthus altissima.  This tree plant toxin has potent post-emergence herbicidal activity and poses a serious weed problem in urban areas.  Sorghum produces sorgolene in most species which disrupts photosynthesis.  Therefore it is being extensively researched as a weed suppressant.  There are many other allelopathic species which include grasses like Rice, Tall Fescue, some Perennial Rye, woody plants as Cherry, Sycamore, Rhododenderon, Elderberry, Fragrant Sumac, and even Pea (Pisum sativum), Goldenrod,  that have allelotoxins.

One way to test for allelopathy is to grow seeds in potentially toxic mulches, compost, or soils.  Use side by side control pots with “clean” soil as a control.  Over time observe germination, growth rate, length of stem and roots, color of leaves, etc. for any sign of toxicity.  “Use What Works” to avoid problems!

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