An Easy Guide to Organic Weed Control

Feed the crop, not the weeds:

Using commercially available synthetic weed control Herbicide-options?

Beware!

You might experience irreversible damage to your well-nourished plants, animals, and the environment, ground and drinking water contamination, and even cancer and devastating birth defects among your loved ones!

Go Organic!

Weeds? The Story!

• Many of these annoying plants we end up plucking from our garden beds are pioneer plants.
• That means it’s their ecological job to restore imbalanced soil to a state of health.
• This is why many weeds either host nitrogen-fixing bacteria – for example, clover, trefoil, and vetch – or accumulate particular mineral nutrients like thistles, dandelions, or plantain.
• They share these nutrients and organic matter with the soil when they die, feeding the soil bacteria and nourishing the soil food web.
• They also support healthy soil ecology by exuding nutrients through their roots while they’re alive, as their determined taproots break up compacted soil and improve tilth.

Weeds are generous givers! Farmers have struggled with the presence of weeds in their fields since the beginning of agriculture. Weeds tend to decrease crop yields by increasing competition for water, sunlight, and nutrients while serving as host plants for pests and diseases. Since the invention of herbicides, farmers have used these chemicals to eradicate weeds from their fields. Using herbicides not only increased crop yields but also reduced the labor required to remove weeds.

Weed Classification:

Summer Annuals: Most well-known example: Crabgrass, Lambsquarters, Mallow, Pigweed, Spurge

Winter Annuals: Most well-known example: Annual Bluegrass (Poa annua), Shotweed, Chickweed, Mustards.

Some of the weeds, you come upon In your daily life are:

Chickweed, Clover (Hop, Red & White), Dandelion, Dollar Weed, English Lawn Daisy, False Dandelion, Florida Betony, Ground Ivy, Lespedeza, Black Medic, Parsley-Pier t, Broadleaf Plantain, Buckhorn Plantain, Virginia Buttonweed, Crabgrass, Barnyardgrass, Foxtail, Black-Eyed Susan, Buttercup, Catnip, Chickweed, Ground Ivy, Jimsonweed, Morning Glory, Poison Ivy, Poison Oak, Ragweed, Sunflower, Thistle, and other broadleaf weeds.

All weeds have a survival strategy and cannot be completely eliminated because they have different life cycles and methods of reproduction.

Seeds can lay dormant for years before they germinate, surviving drought, fire, and herbicide applications.  Even if you were to completely clear a property of seeds, seed, and vegetative propagules can easily be transported to the property by wind, water, animals, or human activity.

Herbicides?

• Yes! They are defined as any substance, individually or in mixtures, whose function is to control, destroy, repel or mitigate the growth of weeds in a crop.
• since the widespread use of agrochemicals has resulted in purported environmental and health problems farmers have a renewed interest in organic methods of managing weeds.
• It has also been found that herbicide use can cause some weed species to dominate fields because the weeds develop resistance to herbicides.
• Besides, some herbicides are capable of destroying weeds that are harmless to crops, resulting in a potential decrease in the biodiversity of farmers.

Pre-emergent timing: Late summer/early fall (rule of thumb is by September 15th)

Pre-emergent herbicides:

• They are designed to control germinating weed seeds.
• Pre-emergent is targeted towards weeds that have not yet emerged from the soil.
• To get the best results and to avoid wasting time and labor costs down the road, the weeds shouldn’t be visible above ground at the time of application.

Important: Pre-emergent is not designed to control existing weeds or weed seeds.

The weed will only be killed when it begins to sprout from the seed and hits the herbicide barrier. It is possible for seeds to remain dormant and not be harmed by the pre-emergent herbicide application. This is why weed control is a constant process. There will always be seeds under the surface and a portion will germinate each season. Annual applications must be made to significantly reduce large infestations.

Pre-emergent must be mixed correctly and applied evenly over the target area for best results. Thorough coverage is key. Think of pre-emergents like a blanket – you need to cover an entire area through which the weed seeds cannot germinate. Spot spraying achieves nothing, as there is plenty of open space for weeds to come through. Manufacturer instructions will indicate how much product to use “per 1000 square feet” or “per acre”,

• Pre-emergent herbicides need to be mixed correctly for the spray solution to be at the appropriate strength. Take the time to read the manufacturer’s recommendations and don’t forget to calibrate your sprayer!
• Watering inactivates the herbicide, creating a barrier just below the surface. Most products call for 0.5 inches of irrigation or rain within 21 days after application.
• If you’re working with a non-irrigated area or a drip zone, apply the pre-emergent just before rain is anticipated.

Remember, pre-emergent herbicide can affect desirable plants. That includes turf.

• Caution must be taken if you’re applying pre-emergent and seeding the turf in the same season.
• Seed first, then apply pre-emergent at least 6 weeks later to allow for lawn establishment.
• Or seed at least 3 months after the pre-emergent has been applied.

Postemergence period: It is the stage between the emergence of a seedling and the maturity of a crop plant.

Post-emergent Herbicides:

1. Post-emergent herbicides are some of the most popular substances for weed control.
2. While pre-emergent herbicides work to prevent weeds from ever-growing, post-emergent herbicides work on weeds that have already grown.
3. They utilize a mixture of chemicals to kill the weed and ensure that it does not grow back.

There are multiple types of post-emergent herbicides available to help eradicate different kinds of weeds in various environments.

1. Systemic herbicides: They are specifically designed to be absorbed into the plant. This ensures that the entire structure of the weed, from the roots upward, is destroyed. They are ideal for stopping perennial weeds from return.
2. Contact herbicides: They are a smart choice when it comes to getting rid of annual weeds. They kill on contact, destroying the leaves and stem of a weed so that it cannot continue to photosynthesize
3. Selective herbicides: They are specifically designed to target weeds without damaging any surrounding grass.
4. Non-selective herbicides: They are typically more powerful, but they usually kill any plants they come into contact with, including grass and other blooms gardeners may want to keep safe.

How to Apply Post-Emergent Herbicides:

1. Methods for applying post-emergent herbicides vary depending on the type of herbicide gardeners want to use.
2. When applying systemic herbicides, simply saturate the ground around the base of the weed with the herbicide.
3. For contact herbicides, it is important to cover all exposed leaves and stems with the substance.
4. Both types of herbicides are potentially very toxic, so it is important to use them only in well-ventilated areas.

Gardeners may also want to wear gloves and use a dust mask when applying herbicides to protect themselves from any direct contact.

Organic system:

Successfully managing weeds in organic systems requires a dramatic change in approach. Simply substituting organic herbicides for synthetic ones rarely works. Knowing your weeds and understanding their damaging potential is a key factor in developing a successful weed management program.

It is important to understand that under an organic system of seed control, weeds will never be eliminated but only managed.

What is an Organic Herbicide?

Herbicides may be inorganic, that is, synthetically created in a lab, or organic, meaning the product is made from chemicals that naturally occur in nature. Both have advantages and disadvantages.

Advantage:

1. Organic herbicides break down quickly, leaving no residual effects, and have low levels of toxicity.
2. Organic herbicides are gaining in popularity due to both environmental and health concerns.

Disadvantage:

1. That being said, organic herbicides for weeds can be expensive for the commercial organic farm or the home grower.
2. They don’t work in every situation and the results are often temporary and/or a reapplication must follow.
3. They are generally used in conjunction with cultural and mechanical weed killer practices.
4. They are non-selective, meaning they cannot differentiate between weeds or basil. Organic herbicides also are most effective on post-emergent plants, those that are currently growing.

Do Organic Weed Killers Work?

• Since they are contact herbicides, they require completely covering the plant with spray. The organic components then remove the waxy plant cuticle or damage cell walls causing the weed to lose too much water and die.
• The effectiveness of these organic herbicides varies depending upon the type of weed, the size, and even the weather.
• These organic herbicides work best on weeds that are less than four inches (10 cm.) tall.
• Mature perennial weeds will likely need multiple dousings and, even then, the leaves may die but the plant may rapidly re-sprout from the undamaged roots.
• For the best results, apply organic herbicides to young weeds on a hot, sunny day.
• Non-synthetic herbicides with no residual activity such as acetic acid (vinegar) can effectively control weeds when applied during hot sunny days. It kills upon contact but does not provide systemic weed control (i.e. not absorbed into the roots).

An optimum weed management strategy often depends on the life cycle of a weed (annual, biennial, or perennial). Weed seeds respond to light, moisture, and temperature. For example, summer annual weeds germinate in warming soils. Thus, implementing and integrating several weed management tactics that include cover crops, higher-density plantings, and mulching between rows with straw would minimize light interception and reduce soil temperatures.

Organic Weed Removal Practices:

Blanket layers of cardboard paper and newspapers

• Plants will grow when they have sunshine and water. Cut off this supply, and you strangle the weeds. Use the black and white pages and avoid the color pages so that you don’t seep chemicals from the ink into your soil. Layer seven sheets of newspaper and wet it down thoroughly to anchor it in place. Cover the newspaper blanket with mulch and form another blanket layer of paper and mulch.
• The paper blankets will break down to their carbon nature and enrich your soil while inhibiting weed growth. If you do see some weeds growing in the mulch, keep repeating the paper blanket process until there is no sign of the pesky plants.

Spray concentrated vinegar directly on weeds

Vinegar has acetic acid which acts as a drying agent when it comes into contact with plant leaves. When you spray vinegar on young plants, the vinegar is more effective because the roots are immature and weak.

Liquid detergent soap:

Soap is an excellent aid in gardening and weed removals. It compromises the surfaces of hairy and waxy weeds, allowing the acetic acid of the vinegar to adhere itself to the leaves. A few drops of liquid soap in your vinegar spray will boost the killing effect of the solution.

Spread some corn gluten meal around your plants

This is a by-product of corn starch and corn syrup and is a competent pre-emergent technique for controlling weeds. It thwarts germination so it must be applied before the weeds start to germinate. Apply it around the plants and seedlings that have taken root in the soil so that the weeds do not have the opportunity to use up the nutrients that your plants require.

Scald the weeds with boiling water

• Pouring water from a boiling kettle onto the weeds will burn them up. This method is especially useful on walkways and paved surfaces since the water gets into all the cracks and spaces quite quickly.
• Trying too hard to get every last weed in a field can waste time, labor, and may do damage to the crop.                                                                  

Solarization: You can also solarize a weedy area by covering it with a layer of clear plastic. This isn’t an herbicide, but it is an effective means of destroying weeds, especially in large areas with no other plants. 

Mow or weed whack any tall weeds and then cover the area during the hottest 6 weeks of summer. Weigh down the edges of the plastic so it doesn’t blow away. After the 6 weeks have passed, the weeds, along with any of their seeds, have been roasted dead. 

Crop rotation:

It is the core of organic weed management. This practice keeps weed communities off balance by mixing cropping systems and long rotations to enhance soil fertility without fertilizers and economic diversity.

Allelopathy:

• Some plant species compete with each other by releasing chemical substances from their roots that inhibit the growth of other plants.
• This “allelopathy” is one of nature’s most effective techniques of establishing plant dominance.
• Allelopathic crops include barley, rye, annual ryegrass, buckwheat, oats, sorghum, Sudan-sorghum hybrids, alfalfa, wheat, red clover, and sunflower.
• Selecting allelopathic crops can be useful in particularly weedy fields with reducing overall weed pressure. Integrating cover crops in your crop and weed management program offers many benefits such as reduced soil erosion, improved soil structure and fertility, and weed suppression.
• Allelopathic cover crops such as cereal rye, sorghum Sudan grass, mustard, and oats inhibit germination of weed seeds.
• In place of a fallow period, plant annual or short-term perennial cover crops.

Timing and Spacing:

Manipulate planting dates to escape weed germination windows or increase seeding density to suppress late-germinating weeds. When perennial weeds are a problem, seasonal cash crops can be rotated with perennial crops that can be mowed or grazed.

Mulch:

Weed-free straw, thick layers of leaf mulch, well-composted manure, or plastic mulch can be used to cover the soil surface. When composting crop residues, manure, or other agricultural wastes, it’s necessary to achieve temperatures above 131°F for a defined period of time to kill weed seeds and human pathogens.   

Flaming:

Flaming can be used as a pre-emergence tactic to control broadleaf weeds from emerging. This practice can be cheaper and quicker than hand weeding.

Variety Selection: Careful selection of crop varieties is essential to limit weeds and pathogen problems and satisfy market needs. It is important to consider planting disease-resistant varieties if certain pathogens are prevalent in the area.

Field Scouting

It involves the systematic collection of weed and crop data from the field (weed distribution, growth stage, population, crop stage, etc). The information is used, in the short term, to make immediate weed management decisions to reduce or avoid economic crop loss. In the long term, field scouting is important in evaluating the success or failure of weed management programs and for making sound decisions in the future.

Is There Any Organic weed control cookbook” to replace the precise herbicide protocols?

An effective organic weed management system cannot be spelled out precisely because ecological weed management is inherently site-specific and responsive to changes in the farm ecosystem.

There is effectively no “organic weed control cookbook” to replace the precise herbicide protocols that have been developed for the conventional production of row crops and some vegetables.

No scientist can come up with a better weed management strategy for a particular farm than the strategy a skillful organic farmer can develop by applying ecological weed management principles to the particular suite of crops, weeds, soil conditions, and available resources on her or his farm.