- Author: Sonia Rios
Shark (carfentrazone) has been currently labeled for use in California avocados. It's widely used in many tree and vine crops. It's a Protoporphyrinogen oxidase (PPO) inhibitor. PPO is an enzyme in the chloroplast cell that oxidizes protoporphyrinogen IX (PPGIX) to produce protoporphyrin IX (PPIX). PPIX is important because it is a precursor molecule for both chlorophyll (needed for photosynthesis) and heme (needed for electron transfer chains). Inhibitors of the oxidase enzyme, however, do more than merely block the production of chlorophyll and heme. The inhibition of PPO by inhibitors also results in forming highly reactive molecules that attack and destroy lipids and protein membranes. When a lipid membrane is destroyed, cell becomes leaky and cell organelles dry and disintegrate rapidly.
PPO Inhibitors have limited translocation in plants and sometimes are referred to as contact herbicides. PPO Inhibitors injure mostly broadleaf plants; however, certain PPO Inhibitors have some activity on grasses. PPO Inhibitors usually burn plant tissues within hours or days of exposure. PPO Inhibitors used in the United States belong to eight different chemistries. It is used in the same niche that Treevix, Venue, and the post rates of Goal are used although registrations vary among those of course (only Goal from that list is registered on avocado).
Carfentrazone is a broadleaf-only herbicide and is interesting in that it has a fairly narrow weed spectrum; it has some species that it is really good on, but misses some other broadleaves almost completely. For example, it is excellent on bedstraw, but pretty weak on fleabane and marestail. It can provide good an inexpensive top-burn of perennial weeds like field bindweed, but will not kill it. Take a look at the label and, if the grower's weed spectrum aligns with some of the labeled weeds, it's worth checking out. Just be aware that it is grass-only and doesn't get all broadleaves equally.
Injury symptoms can occur within 1 to 2 hours after exposure, appearing first as water-soaked foliage, which is followed by browning (necrosis) of the tissue. Symptoms will appear most quickly with bright, sunny conditions at application. Drift injury will appear as speckling on leaf tissue. The necrotic spots are sometimes surrounded by a reddish colored ring. Injury from soil applications or residues appears as a mottled chlorosis and necrosis.
Fig. 1. Phytotoxicity of Shark herbicide on non-target leaf (above)
Phytotoxicity of Shark herbicide on non-target leaf. Since the droplets landing on the
Mixing the formulation depends on the growers sprayer calibration. If applying 20 gal of water per acre, that would be 5 acres per 100 gal mix and would need 10 fl oz product.
For a “spot treatment”, there is a table on the Shark EW label with mix amounts “based on 1 gal of water evenly covering 1000 square feet”. Take a look at Table 4 on this label: https://s3-us-west-1.amazonaws.com/www.agrian.com/pdfs/Shark_EW_Label1q.pdf
- Author: Cheryl Reynolds
UC Statewide Integrated Pest Management Program
The California Department of Pesticide Regulation (DPR) runs the most extensive Pesticide Residue Monitoring Program in the nation and is hard at work ensuring that the fruit and vegetables we purchase and consume are free from illegal pesticide residues. Just last month, DPR detected residues of a pesticide not registered for use on grapes and fined the grower $10,000 for using a pesticide in violation of the label and for packing and attempting to sell the tainted produce.
Cases like this are rare in California but remind growers how important it is to apply pesticides correctly by following all pesticide label directions. Understanding and following label instructions is the focus of a new online course developed by the University of California Agriculture and Natural Resources Statewide Integrated Pest Management Program (UC IPM).
Proper Pesticide Use to Avoid Illegal Residues is targeted to those who apply pesticides or make pesticide recommendations. It explains what pesticide residues are, how they are monitored, and highlights important residue-related information from several sections of pesticide labels. In addition, the course identifies the following as the most important factors leading to illegal residues:
-
Using a pesticide on a crop or against a pest for which it is not registered
-
Applying pesticides at an incorrect rate
-
Ignoring preharvest intervals, re-treatment intervals, or plantback restrictions
Course participants are presented with several real-life scenarios. They must search through actual pesticide labels to determine if the scenario illustrates proper use of pesticides or if the described situation could potentially lead to illegal residues.
The overall goal of this course is to have participants follow pesticide label instructions when they return to the field. Following the label can eliminate incidences of illegal pesticide use.
Proper Pesticide Use to Avoid Illegal Residues is published just in time for pest control advisers and pesticide applicators who are still a few units short to renew their licenses or certificates with DPR. The course has been approved for 2 hours of Pesticide Laws and Regulations continuing education units (CEUs) from DPR and costs $40. If you don't need CEUs, but are still interested in viewing the course content, check it out for free on YouTube.
DPR recommends that renewal packets be submitted before November 1 in order to receive your renewed license or certificate by December 31, as the processing time can take up to 60 days. For additional online courses that UC IPM offers, visit the online training page.
- Author: Cheryl Wilen - Area Wide IPM Advisor
There has been more than the usual number of questions about what I am calling "bio-based" herbicides recently. Arguably, this is coming from news that some school districts and cities specifically calling out the use of glyphosate on the properties they manage. Landscaping departments want to know which of the products available work the best.
To start, please be aware that all of these products are contact herbicides that will not move through the plant. Therefore, they will not be effective if you are trying to get to any underground organ such as the roots, rhizomes, tubers, etc. of any perennial plant. Do not try to make a head to head comparison to glyphosate - glyphosate will win every time. These act more like diquat (Reward) so if you are using Reward, some of these could be a good replacement, if needed.
Here's what I have in:
Suppress* |
CAPRIC ACID + CAPRYLIC ACID |
Finale |
GLUFOSINATE-AMMONIUM |
WeedPharm* |
ACETIC ACID |
AvengerAG* |
LIMONENE |
AXXE*,** |
AMMONIUM NONANOATE |
WeedZap* |
CLOVE OIL + CINNAMON OIL |
Burnout* |
LIMONENE |
Scythe |
NONANOIC ACID |
Fiesta** |
Fe HEDTA |
Roundup Pro |
GLYPHOSATE |
*listed as “organic” but not necessarily OMRI certified
**listed as a biopesticide
I also tried A.D.I.O.S. (active ingredient: sodium chloride + other ingredients: potassium chloride, sodium bicarbonate) in a preliminary experiment and found that it was a waste of my time.
The rates for most of these can be quite high. For example, WeedPharm is applied with no dilution even though it carries a “Danger” signal word on the label. Other are applied at 3-25% rates by volume.
- Author: Oleg Daugovish
Using organic herbicides in production fields and non-crop areas.
The forecasts call for rainy winter and that means a lot of weeds. During dry times perennial weeds tend to grow better than annual weeds, since perennial structures such as underground rhizomes or tubers can support them and give competitive advantage. Seed of annual weeds in dry soil may have been losing viability, senescing or eaten during this time, but many have remained dormant and look forward to the wet winter us much as the rest of us.
Controlling weeds ‘organically' is always an extra challenge whether you are in a certified field or in an area where synthetic herbicides are not desired. Hand-weeding, already expensive, is even a greater burden with limited labor availability, and frankly not much fun either. Of course sanitation and prevention, mechanical and cultural management are essential in organic systems. That requires time and commitment and can quickly become your not-so-favorite pastime.
Organic herbicides have traditionally been contact materials with no systemic activity. This means that they only affect tissue that they contact and do not translocate through the plant like most synthetic herbicides. Thus, good coverage is critical for these contact materials. Many years ago the first herbicides were sulfuric acid and diesel fuel, current organic materials are often acids or oils too, although a lot more benign.
Recent trials by the University of California weed scientists showed that several organic herbicides provided decent control of easy to control pigweed and nightshade when they were small. When weeds were 12 days old, a mixture of 45% clove and 45% cinnamon oil, 20%-acetic acid and d-limonene gave 61-89% control; however only d-limonene controlled 19-day old weeds and none was effective on one-month old ones. As weeds get bigger they also develop a protective cuticle that minimizes efficacy of these herbicides.
This year we conducted trials with a recently OMRI approved herbicide for row crops, trees and vines that is a mix of caprylic and capric acids. It disrupts cell membranes of plans and causes the contents to leak and plants to desiccate. It worked well at 6 to 9% by volume mixture with water and gave 90% control of little mallow and >95% of annual sowthistle compared to untreated checks. We have also tested it in organic strawberry furrows before planting the crop to prevent potential injury from drift. Furrow cultivation does not get close to the plastic mulch that covers the beds to prevent tears, so the weeds in that zone are good target for the herbicide. This fatty acid herbicide provided excellent control of common lambsquarter, reduced the growth of common purslane but didn't do much for yellow nutsedge - one of our notoriously difficult to control perennial weeds (Figure). The bigger weeds need higher rates (9% is the maximum labeled rate) and better coverage. When you have multiple layers of weed leaf canopy and diverse architecture some plants or their parts may be protected by others that intercept the deposition of the herbicide. When on target, this contact material acts fast – you can see results within 2-3 days, however, it does nothing to weed propagules in soil and has no residual activity against wind-dispersed weed seed that fly in after application. This means the control does not last and you will need additional applications or other control measures. Repeated application is not a problem in a non-crop area and is a great way to deplete your weed seedbank, but crop protection from drift, such as shielded sprayers, is necessary to avoid off target plant injury.
Figure. Weed control in strawberry furrows prior to planting with 9% by volume of fatty acid herbicide (top) and weeds in untreated check (bottom)
- Author: Tom Lanini
In recent years, several organic herbicide products have appeared on the market. These include Weed Pharm (20% acetic acid), C-Cide (5% citric acid), GreenMatch (55% d-limonene), Matratec (50% clove oil), WeedZap (45% clove oil + 45% cinnamon oil), and GreenMatch EX (50% lemongrass oil), among others. These products are all contact-type herbicides and will damage any green vegetation they contact, though they are safe as directed sprays against woody stems and trunks. These herbicides kill weeds that have emerged, but have no residual activity on those emerging subsequently. Additionally, these herbicides can burn back the tops of perennial weeds, but perennial weeds recover quickly.
These products are effective in controlling weeds when the weeds are small and the environmental conditions are optimum. In a recent study, we found that weeds in the cotyledon or first true leaf stage were much easier to control than older weeds. Broadleaf weeds were also found to be easier to control than grasses, possibly due to the location of the growing point (at or below the soil surface for grasses), or the orientation of the leaves (horizontal for most broadleaf weeds).
Organic herbicides only kill contacted tissue; thus, good coverage is essential. In test comparing various spray volumes and product concentrations, we found that high concentrations at low spray volumes (20% concentration in 35 gallons per acre) were less effective than lower concentrations at high spray volumes (10% concentration in 70 gallons per acre). Applying these materials through a green sprayer (only living plants are treated), can reduce the amount of material and the overall cost
http://www.ntechindustries.com/weedseeker-home.html
Adding an organically acceptable adjuvant has resulted in improved control. Among the organic adjuvants tested thus far, Natural wet, Nu Film P, Nu Film 17, and Silwet ECO spreader have performed the best. The Silwet ECO spreader is an organic silicone adjuvant which works very well on most broadleaf weeds, but tends to roll off of grass weeds. The Natural wet, Nu Film 17 and Nu Film P work well for both broadleaf and grass weeds. Although the recommended rates of these adjuvants is 0.25 % v/v, we have found that increasing the adjuvant concentration up to 1% v/v often leads to improved weed control, possibly due to better coverage. Work continues in this area, as manufacturers continue to develop more organic adjuvants. Because organic herbicides lack residual activity, repeat applications will be needed to control new flushes of weeds.
Temperature and sunlight have both been suggested as factors affecting organic herbicide efficacy. In several field studies, we have observed that organic herbicides work better when temperatures are above 75F. Weed Pharm (acetic acid) is the exception, working well at temperatures as low as 55F. Sunlight has also been suggested as an important factor for effective weed control. Anecdotal reports indicate that control is better in full sunlight. However, in a greenhouse test using shade cloth to block 70% of the light, it was found that weed control with WeedZap improved in shaded conditions. The greenhouse temperature was around 80F. It may be that under warm temperatures, sunlight is less of a factor.
Organic herbicides are expensive at this time and may not be affordable for commercial crop production. Because these materials lack residual activity, repeat applications will be needed to control perennial weeds or new flushes of weed seedlings. Finally, approval by one's organic certifier should also be checked in advance as use of such alternative herbicides is not cleared by all agencies.