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I do so hope that all of you
loyla loyal followers are having a lovely summer. We here at the
palace (a.k.a. WSU's Pesticide Information Center, a.k.a. PIC) are warm
and weel well. Because things here are Royally Relaxed, I admit
I had somewhat let down my guard about pesticide labels. In fact, I have
been so relaxed that I haven't reminded the U.S. Environmental Protection Agency (EPA) about
my pending appointment as the Queen Bee of Pesticide Labels (that's QBL
to you) in quite some time. (ED. NOTE: Please refer to “If I Were the
Queen of Labels,” AENews Issue
No. 169, May 2000, http://www.aenews.wsu.edu/May00AENews/May00AENews.htm#anchor5232326
, in which HRH QBL introduces Herself as the rightful rulemaker and arbiter
of All Things Concerning Pesticide Labels.)
Hoover However, several labels, also longing lounging poolside,
have managed to force their way into the Queenly Consciousness and I now
see that it is time once again to take fnigers fingers to the keyboard
and issue a short missive.
Before I begin
my latest dignified discussion, this time concerning alleged typographical
(commonly referred to as typos)
errors, I must confess that I too, on rare and royal occasions (and only
sometimes) have been known to have some
troubel trouble with typing.
I konw know that this will surprise my loyal followers but bare
bear in mind, I am, after all, human and I do, very infrequently, make
a mistake. My troubles with typing stem from failing to listen to the
Queen Mum who, years ago, urged Us to take a typing class. Pleas from
the QM of "learn to type so that you will have a skill to fall back
on" feel fell on deaf, albeit majestic and well-shaped (if
I do say so myself) ears. After all, as a future monarch, what need did
I have to tpye type? Should One require tasks of such a nature,
One simply appoints an underling. With a surprising lack of foresight,
I did not anticipate the advent of computers, e-mail, and word porcessing
processing. So, yes, I will admit that the QBL dicsuscing discussing
typos is somewhat akin to the crown calling the jewel showy.
All this aside,
I do not, simply, do not, understand how
regnistarnts registrants can
produce and subsequently distribute, pesticide labels containing typos.
As I know that htere there are no lack of underlings in the world,
I presume that this is also the case among the ranks at the various registrants.
Surely the registrants employ a host of people whose job it is to review
pesticide labels. These people would naturally check for errors to make
sure that no label containing a typo was ever distributed. As we will
see in the flowing following examples, obviously these poople
people either don't exist or they are not being thorough. (As the QM always
used to say "Any job owrht worth doing is worth doing well.")
In the psat past I have gone on and on (and on and on) about EPA's
failings in the area of pesticide label review. Having spent some imer
time onthe on the issue of typeo typos recently, it seems
that now I must expand my flogging to include registrants.
this said, typos on
pesruxusw pesticide labels do make for some
interesting reading here at the PIC. Most of the time these typos result
in scintillating conversation such as "Do you happne happen
to know if boxweed is some type of ornamental?" This conversational
gem was thanks to Bonide's (Trusted Since 1926) Cygon Systemic label.
The label did say boxwood on the frint front cover but when you
really got into the heart of the matter, somehow boxwood had been typmogrified
Trilogy's (now Certis) Deliver Biological Insecticide
me a bit of embarrassment. You see some of these typos are just official-looking
enough to fool the QBL. And, in case it is necessary, please make a royal
note - I do not like to be fooled. The label fro for this product
states that it is for use on "field crop, pop corn, seed corn."
I am embarassed to say that I actually thought they did mean field crop.
You see, in looking at the many labels we see at the PIC we do come across
these all-encompassing label statements (see "QBL
II (No, It's Not a Boat)," AENews Iuuse Issue No. 171,
July 2000). When I called the registrant, ready to go on the Royal
Rant (Just what did they mean by "field crop?" Where was it
defined? Did they have a list?), I was informed that this was simply a
typo and that they had intended the label to read filed cron field
corn, pop corn, and seed corn. It all made so much sense after it was
explained and I must admit to feeling that I had somehow been taken in.
It's just (I assure myself) that I am sensitized to these all-encompassing
label terms and could not see the corn for the trees.
now brings us to the final example that I would like to discuss today:
The label for
Sungent'a Syngent's Ambush 25W Wettable Powder. With
all due repsect respect to the QM, when I first saw this label
I thought that I was looking at the Queen Mother of all typo examples.
In fact I was sure of it.
garphics graphics are scans of various sections of the copy of
the Ambush label that was submitted to the Washington State Department
of Agriculutre Agriculture (WSDA to those in the know). This lable
label was sent to WSDA in October of 2001 as part of the process of registering
a new porduct product for use in the state.
Now I will
admit that I am not as well versed on matters
as some, but what I found on this label somewhat threw me. One thing that
is true of all good lead3ers leaders is that we know when to seek
expert advice. So, faced with insect names that stumped me, I called Dr.
John Brown, the chair of Washington State University's Entomology Departmetn
Department. I explained that I was looking at a label from one of the
major U.S. registrants and that I was sure I was looking at a vast array
of typos. "What? Typos on a Syngenta label? I really doubt it. What
are the naems names of the insects that you are concerned about?"
asked Dr. Brown.
I put forth my first example, "beat" armyworms, I was quite
surprises surprised by Dr. Brown's response. "Ah....beat armyworms.
I can see why you might have thought that this was a typo. Beat armyworms
are very rare now but thye they used to be problematic. They were
prelavent prevalent in the 1950s wghen when they were most
often found in dark, somke smoke-filled clubs and caffee
coffee houses. Perhaps Syngenta, in anticipating their comeback, felt
the need to include these on their label." After a minute's thought
Dr. Brown continued "You know I have a text here that includes some
illustrations of some of the more exotic insects. The drawings are cvery
ggod very good. They are by the famous artist Salí Coãtés. Would you
like me to send you the illustration of the beat armyworm?" Dr. Brown
offered. I acknowledged that this would be most helpful.
that certainly clears up the confusion over the
beet beat armyworms"
I replied, "but what about the mention of leafhippers on the label
under Ornamaentals Ornamentals/Nursery Stock? Certainly that is
Dr. Brown chuckled.
"Boy, Syngenta really is on some type of rare bug kick. Leafhippers
are only found in
urbane urban landscapes in areas of high population
density, fast food, and loud rap music. I seriously doubt that they spens
spend much time hanging around any filed field-grown ornamentals.
That's much too outdoorsie for leafhippers. I am not at all sure why Syngenta
felt the need to discuss the hippers in a field grown context. Luckily
my Salí Coãtés reference includes a leafhipper illustration. I'll get
a copy of that on its way to you also."
By this time
I was feeling a bit disconcerted. Obviously there was more to this entomology
bsiness business than I, the QBL, had ever deined deigned
to give Royal Thought to. Somewhat deflated, I next brought up the coding
moths mentioned in the pear and walnut sections of the Ambush label.
ieemedialty immediately changed at the mear
mere mention of coding moths. "I really don't think that we should
be discussing this over a regular phone line. Let me call you back from
a pay phone."
A few minutes
later, we were reconnected and Dr. Brown continued. "Little is known
about the coding moth. It is
syspected suspected that they were
developed by the government. They are masters of disguise and are most
often found lurking in confidentail confidential fiels files.
Needless to sya say, coding moths lead very secret lives and, consequently,
are diffucult difficult to detect and study. Many of the coding
moth researchers are unavailable for consultation with thise those
interested in this insect. Rumor has it htat that anyone who studies
these bugs has taken a blood oath of sworn secrecy."
It was now time to bring up my last example from the Ambush 25W label. "But Dr. Brown," I inquired, "what about the pea aphides mentioned in the alfalfa section?"
believ e believe that that is a typo."
disucssion discussion had been somehwat discouragin
explained Dr. Brown, "is technically 'pea aphidé.' Apparently the
relatively sophisticated accent mark
ecscaped escaped Syngenta."
Dr. Brown confirmed that pea aphidés spend most of thier their
life cyccle cycle in outdoor cafes along the Champs-Elysées.
thrive on a diet of eclairs, fresh bread, and wine." We both agreed
sis did seem rather odd that Syngenta would mention pea
aphidé on alebel a label sent to WSDA for registration in Washington
State. Dr. Brown wondered how the aphidé could survive. "Washington
produces some very high quality wines, but without the eclairs and the
bread...I just don't see how the little devils could survive and be a
threat to alfalfa."
While it turns
out that I was
wring wrong about the Ambush 25 being the Queen
Mother of all pesticide label typos, the lable label is thought-provoking.
Is Syngenta aware of some pending invasion of exotic insects? Are they
trying to position themselves so that they are the only registrant with
a product on the market that will control pea aphidé, beat armyworm, coding
moth, and leafhipper? Are the only crops that are in danger alfalfa, walnut,
pear, soybean, and ornamentals/nursery stock ( filed field grown)?
There really is only one sensible course of action to follow: I shall
cool the Royal Heels (poolside, of course, and perhaps with a chilled
glass of a fine Washington State chardonnay) and wait to see what develops.
As to the issue
of pesticide label typos, I have one
fnial final word fpr
for registrants: Quit. Stop. Cease. Desist. Hire those underlings. Put
them to work ad and then chuck check their work. Registrants,
be better corporate citizens and quit polluting our file cabinets with
your sloppy work. Thank you. Yours Regally, the QBL. Noted
Notes to the Reader:
For some reason Syngenta does not mention the exotic insects discussed
above in its electronic copy of the Ambush 25W label that can be found
online at the
Greenbok Greenbook Web site or in other electronic
resources. Perhaps the version distributed to WSDA is a special edition!
Dr. Brown has never referred to
nay any insects as "the
little devils." Some literary license was taken with this artiucle
article for the sake of readability.
3. Oh, very well. You caught me. Not only did esteemed professor and department chair Dr. John Brown never say "little devils," Dr. Brown, his heirs, his successors, nor his underlings participated in this article in any fashion. Capisce? I MADE IT UP.
Jane M. Thomas, a.k.a. Her Royal Highness the Queen Bee of Labels, spends her days (when not poolside) at WSU's Pesticide Information Center, where she reigns over the Pesticide Notification Network (http://www.pnn.wsu.edu) while awaiting her Rightful Royal Cornonation with the EPA.
Insect Biological Control of Dalmatian Toadflax in Washington
Dalmatian toadflax, Linaria genistifolia spp. dalmatica, a member of the figwort and snapdragon family, is one bad weed! Like so many other villainous plants encountered in Washington State, this one is not native to North America. It originated in Eurasia and was intentionally introduced into the United States in the 1890s for its ornamental and medicinal value. In no time at all, this aggressive plant escaped from its garden confines and spread to infest farmland, pastures, rangeland, and transportation rights-of-way throughout the country. Today, the most serious infestations are located in the western United States, including Washington State, especially east of the Cascade Mountains.
The weed's high genetic variability enables it to adapt to a wide variety of conditions. It prefers sunny, south- or southeast-facing slopes and sparsely vegetated, sandy or gravelly soils, but it will grow in heavier soils. Disturbed or cultivated ground is highly susceptible to colonization by Dalmatian toadflax. The plant is a strong competitor for soil moisture, especially with winter annuals and shallow-rooted perennials. Its presence in pastures, rangeland, some cropping systems, Conservation Reserve Program (CRP) lands, clear cuts, and natural areas suppresses the development of native and/or more desirable plant species and diminishes land values. Monopolistic stands greatly reduce livestock and wildlife grazing opportunities. Infestations along transportation and utility rights-of-way impede line-of-sight and access and they are costly to manage.
Dalmatian toadflax is classified as a short-lived (three to five years), herbaceous perennial. The plant has a large taproot that can penetrate to a depth of six or more feet. Lateral roots, produced two to eight inches beneath the soil surface, can extend up to twelve feet in all directions from the parent plant. Buds along these roots produce new plants that, after a period of time, become independent of the parent. This vegetative reproduction gives rise to patches of the plant than can persist at a site for over a decade.
Seeds germinate in the fall or spring. Growth begins with a rosette-like mat of short, prostrate, vegetative stems with broad, egg-shaped leaves. The leaves produce sugars required for subsequent root and stem development. The vegetative stems die once flower stem production begins during the spring. The flower stems are upright, robust, and waxy. They are somewhat woody toward the base and branched near the top, and they can grow to four feet in height. An established plant can produce up to twenty-five stems. The alternately arranged leaves are thick and leathery, somewhat heart-shaped with pointed tips, and bluish-green in color with a distinct whitish film or waxy appearance. The leaves tightly clasp the stem and appear to be somewhat crowded together along its length. The upright flower stems are killed by fall frosts but remain standing throughout the winter.
The flowers, produced between May and August, are borne in loose, elongate, terminal racemes (i.e., stalks of flowers arranged singly on an elongated, largely unbranched axis). The individual flowers are similar in structure to a garden snapdragon: three-quarters to one and one-half inches long, bright yellow with an orange "throat"and a long, tubular, downward-directed spur. The petals have two lips; the upper one is two-lobed and the lower one three-lobed. The flowers are pollinated by bumblebees and halictid (small, ground-nesting, dark-colored) bees.
Dalmatian toadflax is a prolific seed producer. Seeds are produced in upright, oval-shaped capsules; each capsule yields from thirty to 250 blackish-brown, pyramid-shaped seeds. Seed production can begin on the lower portions of the stems while upper portions are still in various stages of bloom. A mature plant will often yield half a million seeds. Seed dispersal begins in late June and continues into winter. Dissemination is facilitated by wind, animals, and people. Studies have shown that seeds may remain viable in the soil for at least ten years.
Integrated management of a problematic weed such as Dalmatian toadflax draws upon several approaches. The objective is to reduce the damage caused by the plant while minimizing the negative impact on the environment resulting from the control strategy. In the case of Dalmatian toadflax, it is particularly important to focus upon the prevention of seed formation and vegetative spread. Because the weed is most difficult to manage once it becomes established, it is critical to prevent seed movement from infested to uninfested areas. Once the weed is established, its abundance can be reduced through hand removal, sheep grazing, use of herbicides, planting competitive replacement species, and biological control. Cultivation can be effective, but also contributes to reinfestation by offering a favorable seedbed. The herbicides currently registered for control of this weed vary greatly in efficacy, rarely achieving complete short- or long-term suppression without integration of other control strategies. Further, Dalmatian toadflax often occupies low-value or difficult-to-access lands, which makes herbicide use economically impractical. Consequently, researchers have renewed their efforts to acquire and establish various biological control organisms that effectively suppress populations of the plant in its native homeland.
Weed scientists from Europe, Canada, and the western United States have collaborated to introduce several new Dalmatian toadflax-attacking insects into North America during the last decade. These host-specific natural enemies include the root-boring moths Eteobalea intermediella and E. serratella, the root-galling weevil Gymnetron linariae, and the stem-mining weevil Mecinus janthinus. Of these biocontrol agents, M. janthinus has proven to be the most damaging to Dalmatian toadflax populations thus far.
This beetle was collected in the former Yugoslavia and released in Canada and the United States in the 1990s. The adults are shiny bluish-black, somewhat cylindrical in shape, about one-quarter-inch in length, and have a long snout. They spend the winter inside the previous year's damaged Dalmatian toadflax stems, chewing their way out of them in early May. The weevil is a strong flier and quickly disperses throughout Dalmatian toadflax-occupied areas. Studies at Canadian release sites have shown that M. janthinus has spread over two miles in just four years. Adult beetles use their mouthparts to puncture and feed on the plant's succulent leaves and stems during the early spring. When beetle populations are high, adult feeding usually causes death of the terminal portions of the erect stems, thus inhibiting potential flower development and seed formation.
Depending on weather conditions, females begin laying an egg a day in late May or early June and continue until late July. They typically lay their eggs in flowering stems with diameters of 0.04 inch or greater. Eggs are deposited individually in cavities gnawed in the stems, then concealed with caps of masticated plant tissue to protect them from possible desiccation and predation. Over 100 eggs can be laid in a single stem by different females.
The eggs hatch in six to seven days. The creamy-white, C-shaped larvae immediately begin consuming tissues inside the stems. During the four to five weeks the larvae feed, they tunnel short distances (one-half inch to three inches) within the stems. This mining activity impairs plant vigor by reducing sugar supplies, causes premature wilting of the stems when water-conducting tissues are severed, and suppresses flower bud formation, especially under conditions of high weevil density. Up to 100% of the plants in an area may experience injury from larval feeding once the bioagent becomes well-established. Pupation occurs in oval chambers formed within the mines. Adults emerge several weeks later and proceed to overwinter within the chambers. One generation is completed annually.
A 2001 survey of several northeastern Washington counties revealed M. janthinus' "surprise" occurrence in the state as a consequence of immigration following releases in nearby British Columbia, Canada. It is not known with certainty when the beetles first crossed the border, but a mid-1990s arrival is suspected. Plants were being severely injured at many of the sites examined in northeastern Washington. This is good news for Washingtonians as this natural enemy can now be collected in substantial numbers for relocation to other areas plagued by the weed.
The first intentional release of M. janthinus as a biological control agent in Washington was made in 2000, followed by subsequent releases in 2001. Extensive statewide redistribution of the weevil will occur during the next five to ten years. The beetle by itself may substantially reduce populations of the weed in time, but the importation and release of other approved insect natural enemies along with the coordinated use of additional management tactics will most likely be necessary to further suppress Dalmatian toadflax populations to environmentally acceptable levels in western North America.
Dr. Gary L. Piper is an Entomologist and Biological
Control of Weeds Specialist located at Washington State University in
Pullman. He can be reached at (509) 335-1947 or at firstname.lastname@example.org.
Learning Ways to Control an Invasive Species
Smooth cordgrass (Spartina alterniflora), native to the Atlantic coast of North America, has been widely introduced elsewhere and now has become a problematic invasive species in estuaries throughout the world. Here in Willapa Bay, near Long Beach, Washington, we have one of the largest infestations in the world. In order to determine an effective and cost-efficient strategy for controlling Spartina with minimal impact on non-target species, we evaluated a range of chemical and mechanical strategies over the past six years. Our research has been supported in part by the Washington Commission on Pesticide Registration.
The mouth of a river, the point where it widens and joins the ocean, is known as an estuary. Estuaries serve as rearing grounds for numerous species of fish. They also function as breeding, migration, and wintering habitat for a variety of migrating birds and other wildlife and they form an economic base for many communities involved with commercial fishing, mariculture, tourism, and shipping. Currently, the biological viability of many estuaries is being compromised due to invasion by Spartina. Several species are problematic, including S. alterniflora in the U.S. West Coast and New Zealand; S. anglica in the U.S. West Coast, Europe, Australia, and New Zealand; and S. townsendii in Western Europe and Australia.
Spartina is a perennial, deep-rooted saltmarsh grass that resprouts each year from a dense, persistent root mass. It spreads as a clone through horizontal underground rootstocks known as rhizomes and disperses longer distances by way of broken root fragments and floating seeds. It colonizes several substrates where salinity can range from 1 to 35 parts per thousand. As rhizomes intermingle, circular patches ultimately grow together to form dense meadows that entrap sediments, physically raising the elevation of the tidelands. Marshes colonized by Spartina have exhibited build-up at rates from 2 to 20 cm/year, transforming mudflats into marshes and eliminating much of the upper part of existing tidal flats. Long-term ecological impacts of invasive Spartina marshes include drastic decline in shorebird populations, eelgrass beds, and waterfowl presence.
Control of Spartina is limited by lack of effective tools. New biological, mechanical, and chemical control programs are under development. Recent studies have shown that Spartina populations in Washington can be stressed by the leafhopper Prokelisia marginata. Mechanical control programs have undergone numerous anecdotal evaluations. Multiple mowing has been found to be largely ineffective, but other mechanical methods such as crushing, ripping, tilling, or harrowing show promise as they are beginning to be implemented at some sites in Washington.
Chemical control of Spartina varies by location. Glyphosate, fluazifop-P, and haloxyfop-ethoxyethyl have been used in the United States and England, Australia, and New Zealand, respectively. Rodeo (glyphosate) is the only herbicide registered for aquatic use in an estuary in the United States. The low label rate for aerial applications (3.7 qt/ac) has been ineffective. While the higher label rate for hand application (5% volume-to-volume [v/v] applied at 100 gallons per acre) is more effective, it lacks consistency, is costly (>$1000/ac) and slow (~4 ac/day), and requires exacting weather conditions and expensive airboats for transporting water, equipment, crew, and chemicals. All treated areas in Washington have so far required re-treatment in subsequent years. Research by Sally Hacker at WSU-Vancouver has recently shown that three to four years of follow up are required to gain full control of Spartina anglica in Puget Sound.
The difficulties and time constraints of transporting and applying herbicides to remote and frequently inaccessible tidal marshes will continue to hamper any chemical control program. Without an effective herbicide that can be applied by air or with tracked vehicles using low spray volume, any major progress in Spartina control will remain elusive. And, of course, regardless of efficacy or apparent environmental toxicity profile, all new chemical approaches to Spartina control in the United States must pass regulatory risk assessments.
The focus of risk assessments to date has been on short-term water quality effects, neglecting long-term impacts to habitat. The result is that irreversible ecological damages may be allowed to occur in order to avoid short-term water quality impacts. Shorebird feeding success and survival, for example, depend on the birds' ability to access prey in the upper layer of soft tidal sediment. Management strategies that control Spartina but fail to restore mudflats to their original soft sediment containing ample food sources would have less value than those that did, if one were taking the long view. Risk assessments thus far have failed to evaluate eradication or management cost or the effectiveness of restoring ecosystem function and habitat use.
The objectives of our study were to compare efficacy, environmental risk, non-target impact, cost efficiencies, and habitat restoration of select chemical and mechanical controls of S. alterniflora in Willapa Bay.
We conducted chemical control research under tidal estuary conditions in Willapa Bay, a large, shallow, bar-built estuary, between 1997 and 2001. Herbicide treatments were applied after tidal water receded. We applied herbicides to well-established Spartina meadows in the inter-tidal zone at multiple locations. Plants ranged from 5 to 6 ft. in height at application. The first incoming tide following application usually covered the top of the canopy. "Dry time" before tide coverage ranged from 4 to >24 hours. Applications were usually made in the early morning, with dew present on the canopy, under cloudy conditions. The stage of plant development at application varied from before flowering (late June to mid-July) to after seed drop (October).
We evaluated the herbicides imazapyr and glyphosate, using a crop-oil concentrate with imazapyr and a non-ionic surfactant with glyphosate. We applied Arsenal (imazapyr) at 3 or 6 pt/ac and Rodeo (glyphosate) at 1, 2, or 4 gal/ac using a CO2 backpack sprayer. Spray volume, depending on the treatment, ranged from 10 to 100 gal/ac. We evaluated efficacy based on a visual rating of percent control and stem density compared to an untreated check 9 to 14 months after treatment.
We found imazapyr to be more effective than glyphosate for Spartina control. The low and high rate of imazapyr provided similar control to glyphosate applied at the medium and high rate. For the high rate of each herbicide, there was less variability in control with imazapyr. The lowest rate of glyphosate resulted in little Spartina control. Imazapyr was more effective, more consistent, and required a shorter drying time than glyphosate.
To evaluate short-term environmental risk, we determined concentrations of imazapyr in the water and sediment following applications to bare mud or Spartina through measuring within the sediment and tidal water as it crossed over treated areas. Concentrations of glyphosate, fluazifop-P, and haloxyfop-ethoxyethyl were determined through reviewing available literature. We evaluated immediate maximum concentration (< 3 hours after applications) and short-term concentration (24 to 48 hours after applications), then compared these figures to the most sensitive aquatic invertebrate and fish toxicities, both acute and chronic.
Based on both the literature and the monitoring data, the initial concentration of active ingredients in the tidal water was similar between the products, with the exception of haloxyfop-ethoxyethyl, which was less. After 24 to 48 hours, the glyphosate concentration in the water was reduced 66-fold, but it was still two orders of magnitude greater than imazapyr or fluazifop-P concentration. In sediment, imazapyr had the highest initial concentration, but after several days it equalled that of glyphosate. Fluazifop-P had the shortest persistence in estuary sediment, rapidly decomposing into a less-toxic substance. The initial glyphosate and imazapyr levels in both water and sediment were 1,000- to 10,000-fold below the acute LC50s for fish and aquatic vertebrates (i.e., the concentration that kills 50% of test subjects). The 48- to 96-hour levels were 8,000 to 1,000,000-fold below the LC50s and the chronic NOEL (No Observable Effects Level). Imazapyr had a 15-fold greater margin of safety than glyphosate for aquatic NOEL. For fluazifop-P, initial concentrations were at or near LC50s for fish and aquatic invertebrates, but its decomposition rate is so rapid that there was little potential for aquatic toxicity. The haloxyfop also decomposes quickly to a less toxic form.
We also sought to determine the effects of our treatment on three nontarget species, Chinook salmon, native eelgrass (Zostera marina), and non-native eelgrass (Zostera japonica). For salmon, we tested the potential effect of acute imazapyr exposure on young salmon's abilities to regulate their own internal and external pressure and transmission of fluids, known as osmoregulatory capability; no detrimental effects were shown at the rates 470-fold above the maximum exposure level. For eelgrass, we evaluated the effects of direct applications of imazapyr and glyphosate as a function of location on the tidal mudflats (absence or presence of a tidal water film over the plants at the time of application). Data were collected across multiple sites and times of applications. Results varied considerably between species and location within the tideflat. Z. marina was not affected by herbicides. Z. japonica density was suppressed by both herbicides when applications were made to sites in the tidal flats where the tidal water had completely drained off the eelgrass beds and the foliage did not have a protective film of water over it. Z. japonica was more sensitive to imazapyr than glyphosate. Suppression of Z. japonica was short-lived, however; affected areas were completely re-infested by eelgrass with twelve months after treatment. Overall, applications of herbicides to moist sites had no effect on eelgrass.
To observe mechanical control, we mowed a 200-hectare Spartina meadow 2 to 4 cm above sediment surface during July to October of 2000, then tilled the meadow 4 to 6 cm deep in the winter and spring of 2001. The combination of mowing and tilling resulted in excellent Spartina control (<0.01% ground coverage) when tilling was done in December and January. Tilling February through April reduced ground coverage to 10 to 20%, while tilling in May reduced it to 17 to 50%. The later the tilling occurred, the larger was the size of the Spartina plant clump remaining above the ground.
An additional objective of our research was developing an indication of habitat restoration by observing shorebirds' foraging in treated areas. We observed actual usage patterns among birds on tilled and untilled sites. Data for bird usage of treated areas was monitored for tilled compared to Spartina-infested mudflats during October to January. Average density in a 120- acre tilled meadow was 1973 for shorebird species and 1353 for waterfowl species. Shorebirds were recorded feeding and waterfowl roosting and obtaining shelter during storms. No birds of any species were observed in adjacent Spartina meadows during that time period.
Mechanical and chemical control strategies were evaluated on the basis of initial investment and control cost in dollars per acre that would be required to eradicate a typical 2000-acre Spartina infestation within two years. These evaluations required a great deal of simplification and numerous assumptions. One assumption was that we could obtain good control and achieve eradication within two years. To do this with a combination of mechanical and chemical (glyphosate) control combination required a large upfront investment in equipment (>$800,000) and over $700/acre. Eradication using imazapyr applied via aerial and airboat applications was the least expensive at less than $300/acre. Eradication using glyphosate from a boom off of amphibious vehicle and hand spraying off of an airboat cost a minimum of $460/acre.
Our cost-of-control estimates are conservative. In reality, the dynamic nature of the Spartina invasion would magnify both the overall cost and time period required to eradicate. Oyster growers who have indicated to us that they have been successful in eradicating Spartina from their land say their true costs have been >$6000/ac.
Imazapyr was a more effective herbicide for controlling Spartina across the range of estuary conditions than glyphosate. Effective rates for imazapyr were one tenth those of glyphosate. Spartina control was also more consistent with imazapyr than with glyphosate. Finally, from an operational perspective, imazapyr had the logistic advantage of being effective using one-tenth the carrier volume of water required for glyphosate efficacy. The cost of control is directly related to the quantity of fresh water required for herbicide application.
For both products, the risks to aquatic organisms were negligible: 1,000 to 1,000,000-fold below the LC50 and NOEL for the most sensitive invertebrates and fish species. From an aquatic toxicity profile, these data compared favorably to other herbicides (fluazifop-P and haloxyfop-ethoxyethyl) used for Spartina control elsewhere in the world. From an ecosystem management perspective any effect of imazapyr on nontarget plants would be insignificant. In fact, many estuarine ecologists consider the non-native eelgrass (Z. japonica) to be invasive, therefore any short-term effects of imazapyr on Z. japonica would not be construed as negative.
Mechanical control of Spartina using winter tilling was quite effective. Based on bird usage tilling appears to help restore Spartina-infested mudflats to habitat suitable for shorebird foraging.
To manage large-scale Spartina infestation, the cost-efficiency of the control program must be considered along with herbicide efficacy, aquatic risk assessment, and habitat restoration value. A comparative analysis of different programs is somewhat subjective, as many assumptions must be made in the course of evaluating them. Nevertheless, such an analysis provides an ecosystem manager with the tools to evaluate relative costs.
Our data indicate that by increasing efficacy and reducing the spray volume required to achieve herbicide efficacy, the use of imazapyr is significantly more cost-effective than the use of glyphosate. Although an aerial application of imazapyr may be the most desired method to control large-scale infestations, it is also politically contentious.
In summary, we compared efficacy, environmental risk, nontarget impact, cost efficiencies, and habitat restoration indices of chemical and mechanical control of S. alterniflora in Washington State's Willapa Bay. Chemical control presented negligible aquatic risks. Imazapyr had greater efficacy and cost-effectiveness than glyphosate. Mechanical control was effective in habitat restoration, but not cost-effective.
Kim Patten is with Washington State University in Long Beach. He can
be reached at (360) 642-2031 or email@example.com.
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