Tank Mixing Revisited - Greenhouse Product News

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Tank Mixing Revisited

Recent quantitative research takes a close look at what pesticide mixtures growers are currently adopting.
While popular for its potential to improve pest control, growers should approach tank mixing with caution.

By Raymond Cloyd

Growers mix a wide variety of pesticides in hopes of Pesticides — in this case, insecticides times added to tank mixtures to help manage
achieving success not found with separate applica- and miticides — are used primarily plant diseases.
tions. (Photos: Raymond Cloyd) to control arthropod pests encoun-
tered in greenhouse production There is relatively minimal information cur-
systems. These include greenhouse rently available on the effect of pesticide mix-
whitefly, sweet potato whitefly B biotype, green tures in controlling arthropod pests typically
peach aphid, two-spotted spider mite, western encountered in greenhouses. There is no data
flower thrips, American serpentine leafminer or assessment pertaining to the types of pesti-
and citrus mealybug. cide mixtures (two- and three-way combina-
tions) that greenhouse producers use to control
However, federal rules and regulations, such arthropod pests. As such, we decided to survey
as the Food Quality Protection Act (FQPA), and greenhouse producers at two conferences in
manufacturers’ voluntary withdrawal or can- 2007 and one in 2008, during which the author
cellations have resulted in the continual loss or gave presentations on the fundamentals of tank
registration changes associated with “older” or mixing, to determine the most widely used pes-
conventional, broad-spectrum pesticides, par- ticide mixtures among the participants.
ticularly in the organophosphate and carbamate
chemical classes. This has led to an increase in Survey Distribution and Completion
the development and availability of alternative We distributed pesticide mixture evaluation
pesticides that are more selective or control a nar-
rower spectrum of arthropod pests compared to forms during three sessions at two conferences
conventional pesticides. in 2007: The OFA Short Course on July 14, 2007,
in Columbus, Ohio; and the Greenhouse Expe-
Examples of alternative pesticide groupings rience Conference on Sept. 10, 2007, in Cleve-
include insect growth regulators; insecticidal land. The forms also went out at the Society of
soaps; horticultural oils; selective feeding inhibi- American Florists’ Conference on Pest and Dis-
tors (blockers); microbial agents, such as beneficial ease Management in Ornamentals on March 1,
bacteria and fungi; and related micro-organisms 2008, in Atlanta.
(e.g., spinosad). In addition to their selectivity,
many of these alternative pesticides are less toxic The evaluation forms were provided prior to
to humans, leave minimal residues, are short-lived the start of each session and asked for the respon-
in the environment and have minimal impact on dents’ four most common pesticide mixtures, and
natural enemies, including parasitoids and preda- for what specific insect or mite pests. There were
tors. Although the availability of pesticides that approximately 200 participants in attendance for
demonstrate selectivity may be desirable, this all three sessions, and although not all the par-
presents a dilemma when dealing with multiple ticipants in the three sessions were affiliated with
arthropod pest populations in greenhouses. greenhouse production, a majority — greater than
80 percent — were greenhouse producers.
To regulate or control the myriad arthropod
pests such as thrips, aphids, fungus gnats, leaf- Partial results of the survey are summarized
miners, whiteflies, mealybugs and spider mites in Table 1 (opposite) and represent the first quan-
that feed on ornamental crops, greenhouse pro- titative assessment to determine the pesticide
ducers will mix together two or more pesticides, mixtures conducted by greenhouse producers.
including conventional and alternative insecti- (A full version of the table is available at www.
cides or miticides, into a single spray solution, gpnmag.com.)
which expands the activity of the application.
As such, it may be necessary to tank mix two or A total of 45 fully completed evaluation forms
more pesticides to obtain the same spectrum of were assessed; although 12 of the evaluation
control for multiple arthropod pests that a single forms did not contain the arthropod pests tar-
broad-spectrum pesticide might provide. To fur- geted for the specific pesticide mixtures, they
ther complicate matters, fungicides are some- were still included in the results. The evaluation
form specifically stipulated that only pesticide
mixtures involving insecticides and miticides be

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Top 25 Pesticide Mixtures from Survey Results

TRADE NAMES COMMON NAMES ARTHROPOD PEST(S) COUNT

Two-Way Mixtures 8
6
Avid + Talstar Abamectin + Bifenthrin Mites, whiteflies, mealybugs and aphids 6
6
Avid + Conserve Abamectin + Spinosad Thrips, aphids, and spider mites 5
4
Avid + Ornazin/Azatin Abamectin + Azadirachtin Thrips, spider mites, aphids and whiteflies 3
3
Orthene + Tame Acephate + Fenpropathrin Thrips, caterpillars, whiteflies and aphids 2
2
Conserve + Endeavor Spinosad + Pymetrozine Aphids, thrips, and caterpillars 2
2
Conserve + Pedestal Spinosad + Novaluron Thrips 2
2
Avid + Endeavor Abamectin + Pymetrozine Aphids and mites 2
2
Conserve + Floramite Spinosad + Bifenazate Thrips and mites 2
2
Avid + Flagship Abamectin + Thiamethoxam Aphids, mites and whiteflies 2
2
Avid + Floramite Abamectin + Bifenazate Thrips and mites
1
Avid + Marathon Abamectin + Imidacloprid 1
1
Avid + Mavrik Abamectin + Fluvalinate Aphids and mites 1

Avid + TetraSan Abamectin + Etoxazole Spider mites 1

Avid + Ultra-Fine Oil Abamectin + Paraffinic oil Spider mites

Cleary’s 3336 + Subdue Thiophanate-methyl + Metalaxyl Pythium and thrips

Conserve + Flagship Spinosad + Thiamethoxam Aphids, whiteflies and thrips

Conserve + Marathon II Spinosad + Imidacloprid

Enstar II + Mavrik Kinoprene + Fluvalinate Mites, aphids and mites

Hexygon + Pylon Hexythiazox + Chlorfenapyr Spider mites

Ornazin/Azatin + Talstar Azadirachtin + Bifenthrin Fungus gnats, shore flies and whiteflies

Three-Way Mixtures

Acephate + Azatin + Tame Acephate + Azadirachtin + Fenpropathrin

Avid + Azatin + Pipron Abamectin + Azadirachtin + Piperalin

Avid + Conserve + Decathlon Abamectin + Spinosad + Cyfluthrin Thrips, mites and aphids

Avid + Conserve + MilStop/Compass Abamectin + Spinosad +
Potassium bicarbonate/Trifloxystrobin

Avid + Daconil + Marathon II Abamectin + Chlorothalonil + Imidacloprid

Common name = Active ingredient
Neem oil = Clarified hydrophobic extract of neem oil
Btk = Bacillus thuringiensis spp.. kurstaki
Lure = Attractant
Adjuvant (spray) with the active ingredient: blend of polyether-polymethylsiloxane-copolymer and nonionic surfactant

Table 1. Results of pesticide mixture survey indicating two-, three- and four-way combinations used by the participants. Evaluation forms were distributed at two conferences in 2007 and one in
2008. Forty-five of the 200 distributed surveys were returned.

included, but 13 participants included pesticide chlorfenapyr (Pylon: OHP, Inc.) + acetamiprid and adult) they are most active on are presented

mixtures with fungicides. The return rate of the (TriStar: Cleary Chemical Corp.) two-way mix- in Table 2 (page 24). A number of the miticide

evaluation forms was 22.5 percent (45 out of 200), ture has been shown to provide 86 percent mor- tank mixtures listed in Table 1 were legitimate

which may be considered a small sample size; tality of sweet potato whitefly B biotype nymphs based on the life stage activity of the active

however, the information gathered is useful in 14 days after application. ingredients: abamectin + etoxazole (TetraSan:

determining the extent of what pesticide mix- All the commercially available miticides Valent U.S.A. Corp.), hexythiazox (Hexygon:

tures are being used by greenhouse producers. labeled for use in greenhouses and the two- Gowan Co.) + chlorfenapyr, and abamectin

spotted spider mite life stages (e.g., larva, nymph + clofentezine (Ovation: Scotts-Sierra Crop ➧

Survey Results

The two-way tank mixture cited most often Popular Pesticides
on the evaluation forms — a total of eight times

— was the combination of abamectin (Avid: Syn- Abamectin and spinosad were the pesticides most often included in two-way (abamectin was cited 15

genta Professional Products) + bifenthrin (Tal- times, and spinosad was mentioned 17 times) and three-way (nine mentions for abamectin and seven for

star: FMC Corp.) for control of mites, whiteflies, spinosad) mixtures.

mealybugs and aphids. The other two-way tank Both pesticides are labeled for control of Western flower thrips, one of the most important

mixtures, cited six times by survey respondents, insect pests of greenhouses. In fact, after commercialization in 1998, spinosad is the pri-

were abamectin + spinosad (Conserve: Dow mary pesticide used by greenhouse producers to control western flower thrips due to its

AgroSciences); abamectin + azadirachtin (Azatin: effectiveness against this insect pest although there are now concerns

OHP, Inc., and Ornazin: SePRO Corp.); and regarding resistance. Abamectin, which has been available since

acephate (Orthene: Valent U.S.A. Corp.) + 1980, is commonly used by greenhouse producers to control the

fenpropathrin (Tame: Valent U.S.A. Corp.). two-spotted spider mite, a major arthropod pest of greenhouses.

The two-way tank mixtures of spinosad Several of the two-way mixtures with spinosad including spinosad

+ pymetrozine (Endeavor: Syngenta + abamectin, spinosad + bifenazate (Floramite: OHP, Inc.), and West

Professional Products); and spinosad Two-spotted spider mite spinosad + imidacloprid (Marathon II: OHP, Inc.) did not affect control e r n fl o wer thr ip
+ novaluron (Pedestal: OHP, Inc.) were of western flower thrips.
cited five and four times, respectively. The

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Protection Co.) in Table 2. However, the fol- bifenazate + etoxazole, and hexythiazox + ture for control of thrips, which received two
lowing miticide tank mixtures listed in Table 1 spiromesifen (Judo: OHP, Inc.) in Table 2. counts. Both are fungicides with no insecticidal
were questionable because of similar life-stage activity. The four-way pesticide mixture of abam-
activity of the active ingredients: fenpyroximate One pesticide mixture that was difficult to ectin + spinosad + bifenazate + myclobutanil
(Akari: SePRO Corp.) + clofentezine, fenpyroxi- interpret was the thiophanate-methyl (Cleary’s (Eagle: Dow AgroSciences) was listed for control
mate + etoxazole, abamectin + chlorfenapyr, 3336: Cleary Chemical Corp.) and metalaxyl of mites, aphids, thrips and powdery mildew.
(Subdue: Syngenta Professional Products) mix- However, spinosad is not active on aphids or
mites,and abamectin is labeled only for aphid
Activity of Commercially Available Miticides suppression. A pesticide specifically labeled
for and with demonstrated efficacy on aphids
Active Ingredient Trade Name Activity Type* Eggs Larvae Nymphs Adults should have been included in the mixture.
T and C X X X
Abamectin Avid C X X X X Studies have evaluated the effect of tank mixing
C X X X X pesticides on efficacy against western flower
Acequinocyl Shuttle T and C X X X thrips, two-spotted spider mite and sweet potato
C X X X whitefly B biotype. One study demonstrated
Bifenazate Floramite T and C X X X X that mixing the spinosad with other insecticides
C X X X and miticides (imidacloprid, abamectin and
Chlorfenapyr Pylon C X X X bifenazate) in two-, three- and four-way mixtures
C X X X X did not negatively affect the ability of spinosad to
Clofentezine Ovation C X X X control western flower thrips. Another study eval-
T and C X X X uated the effect of tank mixing the insecticides
Etoxazole TetraSan and miticides buprofezin (Talus: SePRO Corp.),
acetamiprid, chlorfenapyr and bifenazate in two-,
Fenbutatin-Oxide ProMite three- and four-way mixtures on the control of
two-spotted spider mite and sweet potato whitefly
Fenpyroximate Akari B biotype. Overall, most of the tank mixtures did
not affect control of either pest. However, the
Hexythiazox Hexygon buprofezin + chlorfenapyr, and acetamiprid + ➧

Pyridaben Sanmite

Spiromesifen Judo

*Activity Type Codes: C = Contact, T = Translaminar

Table 2. Activity of commercially available miticides for use in greenhouses and the life stages of two-spotted spider mite, Tetrany-
chus urticae, on which they are most effective.

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PATIO CONTAINERS chlorfenapyr + bifenazate tank mix- A “jar test” helps determine whether two pes-
tures resulted in lower sweet potato ticides are incompatible (evidenced by notice-
www.urban-gardener.net whitefly B biotype nymphal mortal- able separation or layering) or compatible
ities (less than 38 percent) than the (evidenced by homogeneous appearance)
For the Retailer other tank mixtures.
not be mixed together in a spray
Ideal for those who don’t have time for a tradi- The survey results demon- solution. Similarly, acephate and
tional garden. strate that greenhouse pro- methiocarb (Mesurol: Gowan Co.),
ducers mix together a diverse despite being in different chemical
Great for small spaces on patios, decks, group of pesticides. However, classes (organophosphates and
porches and balconies. it is not known where or how carbamates), have identical modes
greenhouse producers get the idea of activity. The active ingredient
Floral selection to decorate the outdoor to use specific products in pesticide blocks the action of acetylcholinest-
living area. mixtures. Tank mixing pesticides is erase (AChE), an enzyme that deac-
popular because of the potential for tivates acetylcholine (ACh), which
Vegetables at the doorstep that are fresh improved pest control. But although is responsible for activating recep-
and healthy. there are benefits to tank mixing, tors that allow nerve signals to
there are several issues — discussed travel through the central nervous
For the below in more detail — that growers system. The active ingredients in
Wholesale Grower should consider beforehand. It also both pesticides inhibit or block the
is essential to consider why certain action of AChE by attaching to the
Increased margins over traditional pesticides are being mixed together. enzyme. So, tank mixing these pes-
garden bed plants. ticides should be avoided because
Greenhouse producers need to this exposes the insect pest popu-
Taps into the trends of home deco- develop tank mixtures based on the lation to the same mode of action,
rating and locally grown vegetables. developmental life stage of each pes- which may result in the develop-
ticide’s target pest. For example, tank ment of resistance. This is referred
Offers opportunity for to sell to a mixing two products that have miti- to as cross-resistance.
new clientele. cidal properties, such as abamectin
+ bifenazate, is not recommended Benefits of Tank Mixes
To purchase Urban because both are active on the adult Greenhouse producers often
Gardener growing kits, stage of the two-spotted spider mite
contact one of these (Table 2). However, tank mixing tank mix out of convenience — it
approved Urban Gardener abamectin with either clofentezine is less time consuming, costly and
or etoxazole is appropriate because labor intensive to mix together two
Suppliers: abamectin is primarily active on or more pesticides into a single
adults whereas clofentezine or etox- spray solution and then perform
800-883-0234 azole are active on the eggs, larvae one application compared to two or
www.bfgsupply.com and nymphs (Table 2). These tank more applications. Another reason
mixtures target all life stages of the for tank mixing is the potential for
978-851-4346 two-spotted spider mite. improved pest control or enhanced
www.griffins.com effectiveness. In fact, tank mixing
Considerations two pesticides may result in greater
800-253-0439 for Tank Mixes mortality of arthropod pests than
www.mastertag.com with separate applications.
A concern when tank mixing
The Urban Gardener logo is a registered trademark of Hubie Grown, LLC. pesticides is the potential to Furthermore, tank mixtures
Urban Gardener Patio Containers are protected under patents increase the concentration of sur- may be more effective on certain
(D569, 302), (D569, 304), (D569, 303). factants. Many pesticides already developmental stages of arthropod
Other US and international patents pending contain an adjuvant or surfactant pests. This type of activity is often
©2008 Hubie Grown LLC as a component of the formulation. referred to as synergism or poten-
However, at higher concentrations, tiation. For example, tank mixing
Write in 703 surfactants may be harmful or phy- two different insecticides may
28 GPN D e c e m b e r 2 0 0 8 totoxic to plants. As such, green- result in higher mortality of insect
house producers need to be aware pests, such as western flower thrips
of the consequences of increasing and certain whitefly species, than
the surfactant concentration when when the designated insecticides
mixing pesticides. are applied separately.

Another consideration is the In addition, insecticides con-
need to tank mix pesticides with taining the active ingredient ➧
different modes of action. For
example, although pyridaben (San-
mite: Scotts-Sierra Crop Protection
Co.) and fenpyroximate are in dif-
ferent chemical classes: pyridazi-
none and phenoxypyrazole, respec-
tively. They have the same mode
of action: mitochondria electron
transport inhibitors (METIs), which
disrupt the production of energy or
adenosine triphosphate (ATP). As
such, these two pesticides should

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azadirachtin and the insect-killing or beneficial penetrate the insect. The insect sheds off the spore, vents pesticides from mixing together properly
fungus Beauveria bassiana (BotaniGard: BioWorks; forming conidia along with the old skin. However, in a spray solution. This may result in either a
andNaturalis:OHP,Inc.)appeartobemoreeffective tank mixing azadirachtin with B. bassiana may decrease in effectiveness or phytotoxicity. Incom-
when tank mixed together compared to individual result in synergism or enhanced efficacy because patibility may be due to the chemical or physical
applications. It has been hypoth- azadirachtin, an insect growth regulator, may nature of the pesticides, impurities in the water,
esized that azadirachtin may actu- slow down the molting process, thus allowing the water temperature or the types of formulations
ally “stress” insects, thus enhancing insect-killing fungus to penetrate the target insect mixed together.
the efficacy of the beneficial fungus. For example, pest and initiate an infection.
during the summer months, insect pests such as To determine compatibility between two
thrips and aphids molt or shed their skins (cuti- Concerns Related to Tank Mixes (or more) pesticides, conduct a “jar test.” This
cles) so rapidly that beneficial fungi are unable to Just as synergism improves the efficacy of two involves making a small sample of the spray
solution and placing into an empty jar or other
Tank mixing pesticides is a convenient option for many or more pesticides, the opposite — referred to as container, and allowing the solution to sit for
growers: It’s less expensive and requires less labor than sepa- antagonism — may occur. Antagonism is when approximately 15 minutes. If the pesticides are
rate pesticide applications. mixing two or more pesticides reduces effec- not compatible, there may be a noticeable sepa-
tiveness of the mixture compared to if applied ration or layering, or precipitates such as flakes
separately. In other words, the mixture is less or crystals may form. However, if the materials
effective, based on percent mortality, than indi- are compatible, the solution may appear homo-
vidual applications of each pesticide. It appears geneous or resemble milk. It is important to
that azadirachtin may actually be toxic to certain understand that this procedure only determines
beneficial fungi, thus resulting in antagonism. compatibility, not synergism or antagonism.
In addition to a reduction in effectiveness, there
is also the potential for plant injury or phyto- A concern often affiliated with tank mixing
toxicity. Greenhouse producers need to read pesticides is the prospect of resistance. Although
the label before tank mixing pesticides because this is still not well understood, there is specu-
labels, in general, state which products can and lation that applying two or more pesticides at
cannot be mixed together. different intervals has the same advantages as a
pesticide mixture. However, this is not entirely
Another issue associated with tank mixing true, as each individual arthropod pest in the
is incompatibility, a physical condition that pre- population does not receive a lethal dose or ➧

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concentration of each pesticide, population, and it may be more depends on a number of factors;
and as a result resistance may difficult for individuals in the pop- one of the most important is pre-
evolve more rapidly than with a ulation to develop resistance to vious exposure to either similar or
pesticide mixture. The mecha- several modes of action simultane- different modes of action.
nisms required to resist each ously. However, it should be noted
material in the mixture may not that the ability of arthropod pest In Conclusion
be present in the arthropod pest populations to evolve resistance It is apparent from the survey

Double the Fun Though tank mixing can improve pest con-
trol, it can also lead to incompatibility or even
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and potentially improve control of
arthropod pests (synergism), they
need to be cautious when tank
mixing to avoid problems associ-
ated with antagonism, incompat-
ibility and phytotoxicity.

Additionally, greenhouse pro-
ducers may not be aware of which
pesticide mixtures are compatible.
Although pesticide labels often
state whether certain pesticides can
be mixed, not all combinations can
be evaluated. Because tank mixing
will likely continue to increase,
further research is needed to assess
pesticide mixtures, using the survey
results, that are either synergistic
or antagonistic so that greenhouse
producers can speed up the process
of deciding which pesticide mix-
tures to use and which to avoid.

Acknowledgements
The author is grateful to the OFA

— an Association of Floriculture
Professionals (Columbus, Ohio),
Ball Publishing (Batavia, Ill.) and
the Society of American Florists
(Alexandria, Va.) for making it pos-
sible to conduct the survey during
the designated sessions for each
conference. GPN

Raymond A. Cloyd is associate
professor and extension entomol-
ogist in Kansas State University’s
department of entomology in Man-
hattan, Kan. He can be reached at
[email protected].

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