What Is an Organic Herbicide?
The battle against weed is an eternal one. Weed is one of the reasons maintaining a lawn is tedious work for homeowners. Often, many of us spend long hours pulling the irritating nuisances. You might have considered using an herbicide to make your job easier but are worried about the effect it’ll have on your edible plants, kids, pet, or yourself. It’s time to consider using organic herbicides. Read on to discover what an organic herbicide is and how it works.
Do Organic Herbicides Really Work?
Several organic herbicide products have entered the market in recent years. Weed Pharm (20 percent acetic acid), C-Cide (5 percent citric acid), GreenMatch (55 percent d-limonene), Matratec (50 percent clove oil), WeedZap (45 percent clove oil 45 percent cinnamon oil), and GreenMatch EX are examples (50 percent lemongrass oil). These organic weed control products have some limitations. In this article, I will summarise what we have learned from trials on the efficacy of these herbicides as well as economic considerations for commercial use.
Although these products are appealing for use in sustainable production systems, organic growers should always consult with their organic certifier prior to the intended application, as use of the alternative herbicide may not be approved by all agencies.
Weed Control and Selectivity
Organic herbicides kill weeds that have already emerged but have no residual activity on weeds that emerge later. Furthermore, while these herbicides can kill perennial weeds by burning off their tops, perennial weeds recover quickly.
When weeds are small, these organic products are effective at controlling them, but they are less effective on older plants. We found that weeds in the cotyledon or first true leaf stage were much easier to control than older weeds in a recent study (tables 1 and 2).
If these weeds were exposed to high concentrations of these materials when they were only 12 days old, the control ranged from better than 60% to 100%. When broadleaf weeds were 26 days old, even high volumes of these materials provided only about 40% control.
We also discovered that broadleaf weeds were easier to control than grassy weeds, with only about 40% control on even young, 12-day-old grass weeds. This could be due to the location of the growing point (at or below the soil surface for grasses) or the leaf orientation (horizontal for most broadleaf weeds).
All of these substances are contact herbicides that will harm any green vegetation they come into contact with. They are, however, safe to use as directed sprays on woody stems and trunks. Organic herbicides could be used to prepare the seedbed for turfgrass sod production and then again with the first flush of weeds. To delay turfgrass emergence, plant grass seed a little deeper (1/4 to 1/2 inch deeper) so that the organic herbicide can control the broadleaf flush without harming the turfgrass.
Effectiveness of Organic Herbicides
The question is whether any of these organic herbicides are effective. Because they are contact herbicides, they must be completely sprayed on the plant. The organic components then remove the plant’s waxy cuticle or damage the cell walls, causing the weed to lose too much water and die.
The effectiveness of these organic herbicides varies according to weed type, size, and even weather. These organic herbicides are most effective against weeds that are less than four inches (10 cm) tall. Mature perennial weeds will almost certainly require multiple dousings, and even then, the leaves may die, but the plant may quickly re-sprout from the undamaged roots.
Apply organic herbicides to young weeds on a hot, sunny day for the best results.
Herbicides can be organic or inorganic. When it’s inorganic, it means it’s synthetically manufactured in a lab. Organic herbicides are made from chemicals that naturally occur in nature. Both types of herbicides have their advantages and disadvantages.
Organic herbicides break down quickly and are low in toxins. They’re also very popular due to their environmental and health benefits to both the plant and the soil. But organic herbicides are often reapplied because the result doesn’t last like the inorganic counterpart.
Organic herbicides can’t differentiate between weed and plants. They’re most active on post-emergent weeds (weeds that are currently growing). Therefore, sadly, your days of pulling weeds might not be over, but organic herbicides will reduce the work.
Applying Organic Herbicide
Since most organic herbicides are nonselective, they’re great for eradicating weed from a specific area than using it on the whole garden. The organic herbicide called corn gluten meal is a natural pre-emergence herbicide used to remove grass weed and broadleaf in grasses. To use corn gluten meal, spread around 20 pounds per 1,000 feet of garden to cover the areas you need to weed out. After five days of application, water the applied area well, its effect will last for up to 6 weeks.
How Organic Herbicides Works
Also called contact herbicides, these weed killers kill only the parts of the plant it touches, which is generally everything above the soil level. While it’s enough to kill some plants, it isn’t enough to kill plants that regrow from root fragments. One benefit of contact herbicides is the ability to kill weeds quickly. Some herbicides contain a mixture of both contact and systemic (inorganic) for better weed control.
Some Organic Herbicides Available in Stores
- Vinegar (Acetic acid)
- Corn Gluten Meal (CMG)
- GreenMatch and GreenMatch EX
Weed is something homeowners will continue to battle. These stubborn plants give the home an unpleasant look, not to mention that it competes with the plants in your garden for nutrients and sunlight. Weeding is very time consuming and strenuous, so consider hiring the services of Eden. We have experts on ground to help you get rid of those annoying plants and restore your lawn to the beauty you desire.
Organic herbicides kill only the tissue that comes into contact with them, so thorough spray coverage is essential. In turfgrass production, for example, a large, flat nozzle would be preferable. High concentrations at low spray volumes (20 percent concentration in 35 gallons per acre) were less effective than lower concentrations at high spray volumes in tests comparing various spray volumes and product concentrations (10 percent concentration in 70 gallons per acre). Because organic herbicides have no residual activity, repeated applications will be required to control new weed flushes.
Aside from high volume, we discovered that adding an organically acceptable adjuvant resulted in better control. Natural wet, Nu Film P, Nu Film 17, and Silwet ECO spreader have performed well among the organic adjuvants tested thus far. Although 0.25 percent volume per volume (v/v) is the recommended rate for these adjuvants, increasing the adjuvant concentration up to 1 percent v/v often results in improved weed control, possibly due to better coverage. Work in this area is ongoing, as manufacturers continue to develop more organic adjuvants.
When using organic weed control products, optimal environmental conditions are required. Temperature and sunlight have both been proposed as factors influencing the efficacy of organic herbicides.
We found that organic herbicides work better when temperatures are above 75° F in several field studies, so winter applications may be less effective than summer applications.
Organic herbicides all work if the volume and concentration are high enough to directly contact the weeds. These herbicides, however, are costly and may not be affordable for commercial crop production at this time. In 2010, the cost of broadcast application was approximately $400 to $600 per acre, which may be significantly more expensive than hand weeding. Furthermore, due to the lack of residual activity in these materials, repeat applications will be required to control perennial weeds or new flushes of weed seedlings. We anticipate that these herbicides will be used commercially with camera-based precision applicators that “see” weeds and deliver herbicides only to the weeds, not the crop or bare ground.