Tuesday, March 31, 2015

Imazapyr: Frill Treatments, Cut Stump Application, Hack and Squirt

From: Comments THP 1-14-148MEN, application of herbicide.

Herbicide applications alter the forest ecosystem on all trophic levels. On the microbial level, growth and function are dramatically diminished after herbicide applications. Both the essential bacteria which fix nitrogen in soil, and the micorrhizal fungi which facilitate nutrient uptake by a plant's root system are inhibited by most herbicides. Bacteria and fungi have similar metabolic functions to higher plants, and so are affected by herbicides in similar ways.

After an herbicide application, the early successional plant species which prevent erosion and nutrient leaching from soil die. Loss of their stabilizing root structure leads to an increase in water movement through the soil, increased nutrient loss, and increased erosion from the spray site. In fact, soil nutrient loss from forest areas treated with herbicides has been shown to be greater than loss after either clearcutting or clearcutting followed by burning. The effect of herbicide treatments on soil quality and nutrient uptake by plants is compounded by the persistence of certain herbicides in soil. The half life of the herbicide imazapyr in soil is calculated as 49.5 months,

MRC should consider the news from San Francisco January 12, 2014:
Under the Natural Areas Program, UCSF, which owns and manages most of Mt Sutro Forest, recently decided not to use pesticides there. This may make it the only wild land in San Francisco that is reliably free of pesticides.
http://sutroforest.com/2013/12/12/ucsf-no-pesticides-for-mount-sutro-forest/


IMAZAPYR
"Classified as a Tier II (More Hazardous) chemical by the San Francisco Department of the Environment, this is another pesticide used mainly by NAP. In 2013, NAP accounted for 97% of the imazapyr used by SFRPD. NAP started using Imazapyr even before the SF DoE had approved its use. The main issues with it are that plants push it out through their root system, so that it can spread and affect other plants; it is very persistent. Its breakdown product is a neurotoxin."

According to a BASF Safety Data Sheet from Europe, it’s Harmful to aquatic organisms, may cause long-term adverse effects in the aquatic environment.” However, a BASF Material Safety Data Sheet from the US says, “There is a high probability that the product is not acutely harmful to fish. There is a high probability that the product is not acutely harmful to aquatic invertebrates. Acutely harmful for aquatic plants.”

Imazapyr is sold under the brand name of “Habitat” when it’s for Native Plant Restoration. Its other trade names are slightly less benign: Chopper. Stalker. Arsenal. Assault.

The 2005 Jackson Demonstration State Forest management plan states: Imazapyr is sold under the trade names of Chopper or Arsenal in California.

This product can be applied by air, but primarily is applied by low-volume hand-held spray equipment as a foliar, basal stem treatment, cut stump treatment, tree injection, or frill. It controls plant growth by preventing the synthesis of amino acids. Action is slower than some other herbicides and can take several months or longer. Imazapyr can remain active in the soil for 6 months to 2 years. It is strongly adsorbed in soil and usually found only in the top few inches. Imazapyr is degraded in soils primarily by microbial action. It is soluble in water. It has a low potential for leaching into ground water. Like other herbicides the potential for movement into streams via stormflow can be reduced by utilizing a no-application streamside management zone.

The half-life of imazapyr in water is about 4 days (SERA, 1999b).

Imazapyr is practically nontoxic to fish and invertebrates (Table 1, Ecotoxicological Categories). EPA has approved an aquatic label in some states. Imazapyr is not expected to accumulate or build up in aquatic animals (I.V. 1995). Imazapyr is considered practically non-toxic to mammals and birds (Category IV, Table 1). Its toxicity to bees is believed to be similar to mammals. Risk to non-target plants may be slightly higher than other herbicides because of its soil activity. 

And from: Agricultural Chemistry Research And Extension, Dept of Environmental and Molecular Toxicology; Oregon State University; National Institute of Health Services, Environmental Health Sciences Center - Community Outreach Program, OSU-

For Comparative purposes, the EPA categorizes pesticides by their short term toxicity on a scale of 1 (most toxic) to 4 (least toxic). Most undiluted imazapyr formulations are Toxicity Category 4. "Imazapyr may be persistent in soils. Reported half-lives range from 14 days to 17 months. In forestry dissipation studies, reported values for the half life of Imazapyr range from 14 – 44 days in forest litter, 19 – 34 days in forest soils, and 12 – 40 days on plants.”

Water soluble, it is highly mobile in soils, and can travel through soil with water and enter groundwater. It can also move with runoff and enter surface water. Forestry uses should be evaluated for potential surface and groundwater contamination.”

The EPA advises, not to walk through freshly-sprayed vegetation. Do not eat berries or mushrooms, or other edibles, or drink the water from newly treated areas.”

 

PRACTICALLY NON-TOXIC

It’s water-soluble, and moves through soil to get into groundwater. “Traces of imazapyr were detected in the groundwater even 8 years after application,” according to a study by scientists from the Swedish University of Agricultural Sciences. (Pest Management Science, June 2004.) Full report is incorporated by reference.

"The long‐term fate of the herbicide imazapyr [2‐(4‐isopropyl‐4‐methyl‐5‐oxo‐2‐imidazolin‐2‐yl)nicotinic acid] applied to a Swedish railway embankment was studied. Imazapyr was applied at 750 and 1500 g ha−1 by a spraying train used for full‐scale herbicide treatment operations. Soil and groundwater were sampled twice a year for 8 years after application of the herbicide, and the dissipation of imazapyr was studied by HPLC analysis of the residues in soil and groundwater. A clean‐up procedure including solid‐phase extraction was performed prior to detection by HPLC. Recoveries of imazapyr from soil and water samples were 76–98% and 61–90%, respectively, and detection levels were 0.003 mg kg−1 and 0.05 µg litre−1, respectively. Sorption, desorption and microbial amount and activity were also measured at the two locations. The organic matter content correlated positively and the pH negatively to the adsorption of imazapyr on soil, and increasing organic matter contents decreased desorption. Apart from the 0–10‐cm top layers of both sites, the microbial amount and activity were small. The main proportion of imazapyr was found in the upper 30 cm of the soil, and degraded with a half‐life in the range 67–144 days."

"Small amounts were transported to lower soil layers and to the groundwater in proportion to the amounts applied. Traces of imazapyr were detected in the groundwater even 8 years after application. It was concluded that environmental risks from the use of herbicides on railway embankments could be reduced by including adsorption layers in the embankment during their construction and by reducing the dose of the herbicide used. Copyright © 2004 Society of Chemical Industry - The Fate Of Imazapyr In A Swedish Railway Embankment - Source: Pest Management Science, Volume 60, Number 6, June 2004, pp. 544-549"

While the Swedish study is a broadcast spray scenario, that Imazapyr is pushed out through the roots into the soil is known and is relevant.

What is the environmental fate of the tree foods? Madrone berries, manzanita berries, oak acorns, this must be considered if herbicides are to be applied. The only other timeframe limitation is wet weather and spring (sap flows). The application of herbicides affects foraging for the NSO. With 11 NSO activity centers in the plan, has this concern been considered by MRC and CDFW?

In fact, some plants actually push it out, so it gets into the tangled roots below the soil and kills other plants. From the Nature Conservancy’s Weed Control Methods handbook: “… imazapyr may be actively exuded from the roots of legumes (such as mesquite), likely as a defense mechanism by those plants… the ability of imazapyr to move via intertwined root grafts may therefore adversely affect the surrounding desirable vegetation with little to no control of the target species.”

From: Agricultural Chemistry Research And Extension, Dept of Environmental and Molecular Toxicology; Oregon State University - National Institute of Health Services, Environmental Health Sciences Center - Community Outreach Program, OSU

For Comparative purposes, EPA categorizes pesticides by their short term toxicity on a scale of 1 (most toxic) to 4 (least toxic). Most undiluted imazapyr formulations are Toxicity Category 4.

May be persistent in soils. Reported half-lives range from 14 days to 17 months. In forestry dissipation studies, reported values for the half life of Imazapyr range from 14 – 44 days in forest litter, 19 – 34 days in forest soils, and 12 – 40 days on plants. Water soluble, it is highly mobile in soils, and can travel through soil with water and enter groundwater. It can also move with runoff and enter surface water. Forestry uses should be evaluated for potential surface and groundwater contamination.”

The half-life of imazapyr in water is about 4 days (SERA, 1999b). (JDSF 2005)

From: CalEPPC 2003, Imazapyr: CalEPPC 2003, Considerations for the Control of Invasive Plants - Imazapyr Wildlife Toxicity – Full report is incorporated by reference.

Stalker, Chopper, Arsenal, Habitat

? Quail 8 day diet LC 50 >5000ppm
? Duck 8 day diet LC 50 >5000ppm
? Honey bees LD 50 >100 Mg/bee
? Earth worm 14 day LC 50 >132.5ppm

Imazapyr - Environmental Fate

? Soil half life 25-142 days
? Microbial Degradation
? Water half life 2-3 days
? Soil mobility 12-18 inches vertically/no lateral movement

So we see that impacts to the food chain are inevitable. The chart above is from the EPA and represents toxicity tests where 50 percent died in control groups. That is the legally allowable toxicity level for use. That 50 percent includes a 10 percent natural mortality in control groups. If more than 50 percent die, the active ingredient is not allowed for use.

Mendocino Redwood Company needs to end herbicide use on it's ownership.

From the IMAZAPYR Specimen Label

STUMP AND CUT STEM TREATMENTS
Imazapyr will control undesirable woody vegetation in forest management when applied as a water solution to the cambium area of freshly-cut stump surfaces or to cuts on the stem of the target woody vegetation. Applications can be made at any time of the year except during periods of heavy sap flow in the spring. Tree injection and cut stem treatments are most effective in late summer and early fall. DO NOT over-apply to cause run-off or puddling of spray solution.

APPLICATION WITH DILUTE SOLUTIONS:
For cut stump treatments: Spray or brush the solution onto the cambium area of the freshly cut stump surface. Thoroughly wet the entire cambium area (the wood next to the bark of the stump).

For tree injection treatments: Using standard injection equipment, apply 1 milliliter of solution at each injection site around the tree with no more than one inch intervals between cut edges. Insure that the injector completely penetrates the bark at each injection site.

For frill or girdle treatments: Use a hatchet, machete or similar implement to make cuts
through the bark around the tree at intervals no more than two inches between cut edges.
Spray or brush mazapyr solution into each cut until thoroughly wet.

APPLICATION WITH CONCENTRATED SOLUTIONS:
For tree injection treatments: Using standard injection equipment, apply 1 milliliter of solution at each injection site. Make at least one injection cut for every three inches of Diameter at Breast Height (DBH) on the target tree. For example, a three inch DBH tree will receive 1 injection cut while a six inch DBH tree will receive 2 injection cuts. On trees requiring more than one injection site, place the injection cuts at approximately equal intervals around the tree.

For hack and squirt treatments: Use a hatchet, machete or similar implement to make cuts
at a downward angle completely through the bark and cambium at approximately equal intervals around the tree. Make at least one cut for every 3 inches of DBH on the target tree as described above, using a squirt bottle, syringe, or similar device apply about 1 milliliter of concentrate solution into each cut, ensuring that the solution does not run out of the cut.

It is a violation of Federal law to use this product in a manner inconsistent with its labeling.

Employ People, Not Poisons
Tomas DiFiore