Astm stp 875 1975

The five papers in the Formulations section cover the role of anionic surfactants, seed treatment formulations, computerized optimization of emulsions, tank mix compatibility of pesticid

on Pesticides New Orleans, La., 2-3 Nov 1983

ASTM SPECIAL TECHNICAL PUBLICATION 875 Thomas M Kaneko, BASF Wyandotte

Corporation (retired), and Larry D Spicer, Rhone-Poulenc Chemical Company, editors

ASTM Publication Code Number (PCN) 04-875000-48

#

1916 Race Street, Philadelphia, Pa 19103

Pesticide formulations and application systems

(ASTM special technical publication; 875)

"ASTM publication code number (PCN) 04-875000-48."

Papers presented at the Fourth Symposium on Pesticide

Formulations and Application Systems

Includes bibUography and index

1 Pesticides—Congresses 2 Pesticides—AppUcation

—Congresses I Kaneko, T M (Thomas M.) II Spicer,

Larry D III ASTM Committee E-35 on Pesticides

IV Symposium on Pesticide Formulations and Applications

Systems (4th: 1983 : New Orleans, La.) V Series

Printed in Ann Arbor, Mich

September 1985

Foreword

The Fourth Symposium on Pesticide Formulations and Application

Sys-tems was held in New Orleans, Louisiana, on 2-3 November 1983 ASTM

Committee E-35 on Pesticides sponsored the event Thomas M Kaneko,

BASF Wyandotte Corporation (retired), served as symposium chairman;

Larry D Spicer, Rhone-Poulenc Company, served as symposium co-chairman

Both men have edited this publication

A Note of Appreciation

to Reviewers

The quality of the papers that appear in this publication reflects not only the

obvious efforts of the authors but also the unheralded, though essential, work

of the reviewers On behalf of ASTM we acknowledge with appreciation their

dedication to high professional standards and their sacrifice of time and effort

ASTM Committee on Publications

Allan S Kleinberg Janet R Schroeder Kathleen A Greene Bill Benzing

Contents

Introduction 1

FORMULATIONS Phosphorus-Based Anionic Surface-Active Agents and Their Role in

Agrochemical Formulations—G. P SHERIDAN 5

Seed Treatment Formulations: Development of a Protocol—

c G (BERT) HALLIDAY 15

Evaluation of Factors Affecting Tank Mix Compatibility of Pesticide

Combinations—w E BRENNER, L J BROWN, AND

I E MACHADO 24

A Method for Emulsion Optimization Through Computerized Regression

Analysis—J E LOHR, JR 37

A SmaU-Scale System to Evaluate Anti-Foam Performance—

R FRANK AND T L HAZEN 5 0

APPLICATIONS Initial Studies on the Effects of Droplet Size and Electrostatics on Spray

Deposition Efficiencies—F. R HALL AND D L REICHARD 61

Efficacy of Insecticides Applied Ultra-Low Volume in Vegetable Oils—

R G L U T T R E L L 6 7

Use of Electrostatics, Rotary Atomizers, and Vegetable Oils in

Low-Volume Ground Application—L. E BODE, B I BUTLER, AND

L M WAX 7 8

Control of Spruce Budworm by Ultra-Low-Volume Application of an

Injection of Chemicals for Subsurface Drip Irrigated Cotton—

s TOLLEFSON 98

Evaluation of Plant Growth Regulators—T. F ARMSTRONG 109

Effect of Fonnulation and Pressure on Spray Distribution Across the

Swath with Hydraulic Nozzles—H. R KRUEGER AND

D L REICHARD 113

The Laboratory for Pest Control Application Technology (LPCAT):

A New Interdisciplinary Approach for Solving a Difficult

Problem—F R HALL 122

GRAITOLES Development of Toxic Baits for Control of Imported Fire Ants—

Determination of the Liquid Holding Capacity (LHC) or Sorptivify of

Agricultural Carriers—E. W SAWYER AND R J PURCELL, JR. 167

SUMMARY Summary 185

Index 189

STP875-EB/Sep 1985

Introduction

The Fourth Sjrmposium on Pesticide Formulations and Application

Sys-tems was held on 2-3 November 1983 in New Orleans, Louisiana Like the

previous three similar symposia (Philadelphia, 1980, ASTM STP 764;

Kan-sas City, 1981, ASTM STP 795; Fort Mitchell, Kentucky, 1982, ASTM STP

828) it was sponsored by ASTM Committee E-35 on Pesticides and organized

by Subcommittee E35.22 on Pesticide Formulations and Application

Sys-tems The goals of this series are as follows:

1 Provide an open forum for presentations, discussions, and

state-of-the-art review, covering the area of pesticide formulations, application systems,

and related topics

2 Allow for exchanges of ideas and discussions of problems confronted by

manufacturers, shippers, applicators, and regulatory agencies

3 Include a wide variety of topics in each symposium, such as formulating

and testing procedures, container selection, storage stability ^-equipment and

application techniques, and their relationships to pest control efficiency

4 Discuss advances in overall techniques to improve the quality and yield

of crops

The papers in this volume are grouped into three sections: (1)

Formula-tions, (2) ApplicaFormula-tions, and (3) Granules The five papers in the Formulations

section cover the role of anionic surfactants, seed treatment formulations,

computerized optimization of emulsions, tank mix compatibility of pesticide

combinations, and evaluation of antifoam performance In the Applications

section are nine different papers; the subjects discussed include applications

of electrostatic spraying using water or vegetable oils as carrier for the

pesti-cide in low-volume and ultra-low-volume applications, chemical injection for

subsurface drip irrigation, evaluation of plant growth regulators, and

labora-tory research techniques for pesticide delivery systems Finally, the Granules

section contains a paper each on the topics of carrier-based toxic baits for

control of fire ants, development of water dispersible granules, dry

applica-tion of dry flowables, and sorptivity determinaapplica-tion of clay carriers

As was done for earlier symposia, the program was designed to appeal to

the entire audience, which consisted of people representing industry,

aca-demia, applicators, regulatory agencies, and research institutions The

en-thusiasm and keen interest expressed by the audience led the committee to

expand the symposium to cover two full days

This Special Technical Publication gives the reader a state-of-the-art

over-view of pesticide formulations and application systems The subject matter

covered by the papers reported herein indicates the broad scope of the

sympo-sium This volume is expected to serve as useful reference for anyone involved

in the formulation, manufacture, distribution, and application of pesticides

Formulations

Phosphorus-Based Anionic

Surface-Active Agents and Their

Role In Agrochemical Fornnulations

REFERENCE: Sheridan, G P., "Phosphorus-Based Anionic Surface-Active Agents and

Their Role in Agrochemical Formulations," Pesticide Formulations and Application

Sys-tems: Fourth Symposium, ASTMSTP875, T M Kaneko and L D Spicer, Eds.,

Ameri-can Society for Testing and Materials, Philadelphia, 1985, pp 5-14

ABSTRACT: Phosphorus-based anionic surfactants prepared by reacting an alcohol or

an ethoxylate with tetraphosphoric acid (TPA) or with phosphorus pentoxide (P2O5) are

complex in structure, yielding differing compositions of mono- and diprotic species of

alkyl phosphates When surfactants prepared from TPA-based product and P205-based

product are compared, it is seen that whilst the free alcohol content is essentially the

same, the monoester content has been considerably increased at the expense of the

"di-protic" or polyphosphate species The properties exhibited by these surface-active agents

can be directly attributed to these structural differences and are particularly emphasized

in the formulation of agrochemicals Phosphates prepared using P2O5 can be of

signifi-cant advantage in the formulation of emulsifiable concentrates and suspension

concen-trates where the influence of the diprotic species assists emulsion stability and dispersion

rheology, whereas the TPA route is preferable in circumstances involving high electrolyte

conditions such as fertilizer solutions

KEY WORDS: phosphorylating agent, tetraphosphoric acid, phosphorus pentoxide,

phosphate esters, emulsifier, dispersant, hydrotropic properties, suspension concentrate,

fertilizer, active ingredient

The organic phosphates under discussion are those normally prepared by

reacting an alcohol or an ethoxylate with the so-called tetraphosphoric acid

(TPA) or with phosphorus pentoxide (P2O5) The chemistry of the formation

of these phosphates is complicated, which makes it difficult to assign precise

formulas to their composition It is certain, however, that the composition

and properties of the alkyl acid phosphates are significantly different when

prepared using different phosphorylating agents In order to properly discuss

' Section Leader, Surfactant & Surface Coatings, Lankro Chemicals Ltd., a subsidiary of

Dia-mond Shamrock Europe Ltd., Eccles, Manchester, England

6 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

the effect these will have on agrochemical formulations practice, it is essential

to briefly discuss the chemistry of the compounds with which we are

con-cerned

The chemistry of the preparation of alkyl acid phosphates using TPA is

reasonably well understood following the work of Clark and Lyons [/]

Te-traphosphoric acid is essentially a mixture of polyphosphoric acids of the

that the reaction between a hydroxylic compound and TPA proceeds via the

attack of the - O H on the - P - O - P bond:

O

II ROH + H - ( 0 - P ) n - O H — ^

formed (via attack from both ends of the chain), then this molecule would not

cleave further The resulting product therefore contained free

orthophospho-ric acid, monoalkyl ester, and dialkyl pyrophosphate ("diprotic species")

The evidence for this postulate was supported by the absence of di-ester and

middle-group phosphorus in analysis by NMR

Analysis of products prepared using TPA as phosphorylating agent tends

to confirm the proposed mechanism Calculation by the results from

7 7.7

> 7 18.9

tions using standard alkalis and based on the foregoing premises gives the

following approximate results for a typical phosphated alcohol:

_%

Monoalkyl phosphates: 0 - P ( O H ) 2 OR 68

OH

I Dialkyl pyrophosphate: 0 = P —OR 2

As can be seen, there is a preponderance of monoester, a significant amount

of free orthophosphoric acid, and only a small amount of the diprotic

pyro-phosphate

The alkyl acid phosphates prepared using phosphorus pentoxide as

phos-phorylating agent are less completely defined The structure of phosphorus

pentoxide is still open to some discussion There is good evidence to show that

some forms of the oxide exist as tetrahedral structures of P4O10, but the

nor-mally commercially available material probably also contains high and very

high polymeric material It is therefore advisable, and convenient, to retain

the formulation P2O5 for general usage

It can be assumed that the alcoholysis of highly polymerized chain

po-lyphosphoric oxides will generally follow the paths outlined for TPA, but the

alcoholysis of the tetrahedral P4O10 and other ring polyphosphoric oxides can

theoretically follow a number of different reaction paths, giving rise to a

num-ber of different product mixes This is reflected in the fact that if the

guide-lines used for the alcoholysis of TPA are used here, it is difficult to totally

reconcile the theoretical compounds with the results obtained by conventional

analysis Typical results can be summarized as:

Monoalkyl phosphate: 0 = P ( 0 H ) 2 OR 35 Orthophosphoric acid: 0 = P ( 0 H ) 3 1 Free alcohol: ROH 22

"Polyphosphates" by difference 42

8 PESTICIDE FORRMULATIONS: FOURTH SYMPOSIUM

Whatever the true interpretation of the results, they indicate that the

com-position of a phosphate prepared from phosphorus pentoxide differs

signifi-cantly from that prepared from TPA When the results are compared with

those obtained from a TPA-based product, it will be seen that whilst the free

alcohol content is essentially the same, the monoester content has been

con-siderably reduced at the expense of an increase in the "diprotic" or

polyphos-phate content These differences are usually carried through into the

practi-cal uses of the products where the different compositions are found to be more

or less effective in different applications

Properties and Applications of Phosphate Esters

We have already explained that alteration in the type of phosphorylating

agent used can considerably alter the structural properties of the surfactant

molecule and consequently change the surface-active nature of the resultant

phosphated compound Similarly, alteration of the ratio of base compound to

phosphorylating agent can alter the surfactant properties However, there are

certain general properties that can be identified with phosphated nonionic

alkoxylates Some examples follow

Solubility

Phosphated surfactants are much more hydrophillic in character than their

nonionic bases, although they can still retain similar solubility in both polar

and nonpolar solvents Examples are given in Table 2

Certain phosphated nonionic surfactants in their free acid form can be

in-soluble in water, whilst their corresponding alkali metal salts exhibit water

solubility This is an important property that accounts for the increased

bility of phosphated surfactants in a wide variety of alkali electrolyte

solu-tions, which is considerably better than that of the corresponding base

non-ionic and many annon-ionic surfactants of the sulfate or sulfonate type (Table 3)

TABLE 2—Solubility

Product

Mineral Methylene Kerosene Oil Xylene Chloride Isopropanol Nonyl phenol + 9 moles EO insoluble insoluble

° Phosphated nonyl phenol + 9

moles EO insoluble insoluble

Lauryl alcohol + 3 moles EO soluble soluble

* Phosphated lauryl alcohol +

3 moles EO soluble soluble

soluble soluble soluble slightly turbid

soluble soluble soluble soluble

soluble soluble soluble slightly turbid

" Reaction product of 2 moles nonionic to 1 mole tetraphosphoric acid

* Reaction product of 3 moles nonionic to 1 mole tetraphosphoric acid

TABLE 3—Electrolyte concentration

Electrolyte Concentration

soluble soluble insoluble soluble soluble soluble

10%

insoluble soluble insoluble soluble soluble insoluble

15%

insoluble soluble insoluble soluble insoluble insoluble

Nonyl phenol + 9 moles EO

Nonyl phenol + 9 moles EO phosphate

Lauryl alcohol + 7 moles EO

Lauryl alcohol + 7 moles EO phosphate

Nonyl phenol + 9 moles EO sulfate

Alkyl benzene sulfonate

Surface Active Properties

Surface Tension and Wetting—As a direct result of the increased

hy-drophilicity, they are generally inferior in surface tension depression and

wet-ting properties than the base nonionic from which they are derived At high

temperatures and in electrolyte conditions, however, they do not suffer from

the inverse solubility (cloud point) effects and become more effective under

such conditions This is illustrated by the results in Table 4

Foaming—Foam produced by phosphated nonionic surfactants is only

slightly higher than that formed by the base nonionic although it is somewhat

more stable The foam profile is substantially lower, however, than that

ex-hibited by sulfonated or sulfated products and generally the salts foam more

than the free acids (Table 5)

It is clear that the chemistry of this class of compounds is so versatile that

the hydrophiUic-lipophillic balance and surface properties can be controlled

Several important properties are directly attributable to the presence of the

phosphate radical, and included amongst them are:

• Improved electrolyte tolerance

• Heat and alkali stability

Nonyl phenol + 9 moles EO

Nonyl phenol + 9 moles EO phosphate

Lauryl alcohol + 7 moles EO

Lauryl alcohol + 7 moles EO phosphate

31.8 35.5 30.3 37.0

34.5 34.0 33.7 3.42

8.0 29.0 20.0 17.0 7.5 31.5 26.0 21.5

"Measured by Du Nouy tensiometer in dynes/cm

* Measured by modified cotton tape test (see Ref 2) in the presence of 1% sodium chloride

10 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

TABLE 5—Foam height

Product Nonyl phenol + 9 moles EG

Nonyl phenol + 9 moles EC phosphate

Lauryl alcohol + 7 moles EG

Lauryl alcohol + 7 moles EG phosphate

Nonyl phenol 4- 9 moles EG sulfate

Alkyl benzene sulfonate

One can readily identify the advantages of such multifunctional properties in

the formulation as well as the application of agrochemicals whether as

emul-sifiers to improve the robustness of emulsifiable concentrates to differing

wa-ter hardness conditions, as dispersing agents to enhance the stability and

rhe-ological properties of suspension concentrates, or merely as an external tank

addition to ensure successfully spraying combinations of pesticides and

fertil-izers

Formulation Development

Optimization of these properties is, however, dependent upon the factors

already described such as chemical structure and product composition The

practical examples which follow should serve to illustrate how a formulator

must be aware of such factors when commencing his formulation

develop-ment

If we consider then an emulsifiable concentrate where the active ingredient

is solubilized in a preferred solvent, certain minimum requirements are

nec-essary The concentrate should be chemically stable and readily dilutable in

water with minimum agitation to provide spray strength emulsions stable for

the duration of the spray tank storage Such requirements are not always

eas-ily attained if one introduces widely differing water hardness conditions,

dilu-tion in fertilizers, or the presence of several active ingredients in the same

concentrate Phosphate ester surfactants can be used to overcome these

diffi-culties, but production route is essential to achieving the best possible results

This can be shown by the properties given by two formulations involving the

organo-phosphorus insecticide Malathion (Table 6) Both these concentrate^

were diluted at 5% v/v in test solutions containing 50 to 1000 ppm water

hardness at 30°C (Table 7) These results and the evidence amassed from

TABLE 6—Properties of two Malathion formulations

60% w/v Malathion (tech)

7.5% w/v Agriwet PC (high mol weight

ethylene oxide, propylene oxide copolymer)

2.5% w/v Agriwet UE (nonyl phenol + 4 E 0

P2O5 prepared phosphate)

to 100 vols xylene

60% w/v Malathion (tech) 7.5% w/v Agriwet PC 2.5% w/v nonyl phenol +-4EO TPA-prepared phosphate

1 cream

1 cream 1.5 cream

Stability

2 h stable stable stable stable trace cream stable

3 cream

5 oil/cream

5 oil/cream

5 oil/cream

Others show the advantages of a P2O5 prepared phosphate over a TPA

pre-pared phosphate albeit initiated from the same nonionic ethoxylate

In suspension concentrates they can be used to advantage, once again, to

enhance stability in dilution waters However, they can if chosen correctly

have a remarkable effect on the processing of such formulations and the

phys-ical properties of the finished concentrate

Suspension concentrates are usually prepared by premixing active

ingredi-ent(s), adjuvants (dispersants, wetters, defoamers, etc.) in a carrier medium,

usually water, and wet grinding using horizontal bead milling equipment

The rheology of the suspension is of vital importance in determining the

maximum active ingredient concentration attainable, the ease of

manufac-ture, and the ultimate stability and dosing of the finished formulation Our

work in the area of suspension concentrate formulation with these

phos-phated compounds has taken into account the hydrophobe type as well as the

phosphation route, the latter proving to be the most

performance-determin-ing factor We can compare this effect by studyperformance-determin-ing the viscosity profile of a

suspension concentrate against adjuvant concentration using sulfur at 800

g/L concentration The active ingredient was agitated in a high-speed mixer

12 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

(5000 rpm) in the presence of wetter/dispersant, antifoam antifreeze

com-pound, and water The premix was then milled to effect a particle size of

approximately 3 to 4 /im using a horizontal bead mill The optimum amount

of phosphate ester was determined by measurement of viscosity against

per-cent conper-centration of dispersing agent See Fig 1

These results with sulfur have been repeated with many other active

ingre-dients and their mixtures and suggest that the P2O5 phosphated or products

with a higher "diprotic" species are a more economical and effective additive

for the preparation of aqueous suspension concentrates

In the previous two examples we were able to show the advantages of

phos-phate ester surfactants as primary adjuvants for agrochemical formulation

However, there are many occasions where existing registered formulations

based on more conventional emulsifiers or dispersants need to be adopted to

meet the more severe conditions encountered in multispraying operations

The conditions encountered in the simultaneous spraying of liquid fertilizers

and toxicants is a good example

Many formulations are not designed to dilute readily to meet regulation

stability in such conditions Therefore the result can be the formation of

cream or oil separation in the case of emulsifiable concentrates or flocculation

of the active ingredient in the case of wettable powders or suspension

concen-trates

The use of phosphated surfactants is well known in this field of so-called

"compatibility agents," particularly in the United States, where they are

mar-keted as aids to stabilize emulsions and dispersions by tank additions in the

presence of fertilizer solutions In such a situation one does not want to

inher-ently change the performance of the original formulation but merely retain it

under different and more severe electrolytic conditions A comparison will

show that the hydrotropic properties of phosphated surfactants are ideally

suited to cope with this problem and in particular those manufactured via the

tetraphosphoric acid route

Once again a comparison can be made by taking a proprietary fertilizer

compounded from 40% ammonium nitrate, 32% urea, and 28% water To

95 mL of this test liquid was added 5 mL of an emulsifiable concentrate based

on 400 g/L Diazinon and a suspension concentrate containing 800 g/L sulfur

Further experiments were carried out incorporating a "compatibility agent"

in the form of phenol +4 moles ethylene oxide phosphated by both

phos-phorylating routes with results Table 8

TABLE 8—Formulation types and compatibility agents

Appearance After 1 h Formulation Compatibility

Type Agent Zero 0.1 0.2 0.3 0.4 0.5

Diazinon EC phenol 4EO (TPA) immediate oil 2.0 stable stable stable stable

phosphate separation cream

phenol 4EO (P2O5) < Immediate oil >• 5.0 3.0

phosphate separation cream cream Sulfur SC phenol 4EO (TPA) immediate slight stable stable stable stable

phosphate flocculation sediment

phenol 4EO (P2O5) -< immediate flocculation *• flocculation

phosphate after 15 to 30

14 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

Conclusions

The evidence presented in this paper is not intended as a means of

intro-ducing agrochemical formulators to the use of phosphated surface-active

agents as those we know are already used It is merely to emphasize the

com-plex structure of those compounds that can be altered by choice of

phosphory-lating agent, the knowledge of which can be very useful in seeking out the

most effective one for a given application

Acknowledgments

I wish to thank Dr D R Karsa and Mr T Fay of Diamond Shamrock

Europe and acknowledge their contributions to this paper

References

[/] Clark and Lyons, Journal of the American Chemical Society, VoL 88, No 4, pp 4401-4405

[2] Ashworth and Lloyd, Journal of the Science of Food and Agriculture, Vol 12, 1961, p 234

Seed Treatment Formulations:

Development of a Protocol

REFERENCE: Halliday, C G., "Seed Treatment Formulations: Development of a

Pro-tocol," Pesticide Formulations and Application Systems: Fourth Symposium, ASTM

STP 875, T M Kaneko and L D Spicer, Eds., American Society for Testing and

Mate-rials, Philadelphia, 1985, pp 15-22

ABSTRACT: Since the late 1940s, and perhaps even earlier, pesticidal compositions to

treat seeds prior to planting, for the control of certain fungi as well as soil insects, have

been developed and manufactured Until the late 1960s, organo-mercury compounds

dominated the seed treatment field, especially in the treatment of cereals (wheat, barley,

etc.) With the banning of organo-mercury compounds for seed treatment use by various

governments throughout the world, a new breed of fungicidal compounds was developed

for treating seed, with many of these having systemic properties This paper describes

briefly a protocol for the development of seed treatment formulations which has been used

successfully by the author over the last 15 years The protocol outlines the desirable

physi-cal and chemiphysi-cal properties of these types of pesticide formulations as well as laboratory

storage and field tests which it is felt are required

KEY WORDS: seed treatments, pesticide, formulations, protocol

The use of seed treatments dates back to 60 A.D where Pliny described the

use of wine and crushed cypress leaves for this purpose [1,2] In 1637

Rem-nant [2] described a seed treatment for bunt It is obvious from this that

farmers, prior to the chemical age, recognized that there were diseases and

possibly insects in the soil which affected the germination of seeds and hence

their yield of certain crops

Up until the advent of the organo-mercury compounds such as "New

Im-proved Ceresan" (5% ethyl mercury phosphate), which appeared in 1933,

and "Ceresan" M (7.7% 7V-(ethylmercuri)-p-toluene sulfonanilide in 1948,

seed treatments were mainly simple inorganic compounds such as copper

salts and their solutions and brine Then came mixtures of phenyl mercury

acetate/ethyl mercury chloride, and eventually methyl mercury

dicyandiam-'Laboratory Manager, Chipman Inc., Stoney Creek, Ont., Canada

16 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

ide and methyl mercury nitrile These mercury compounds were used at very

low application rates (21.3 mL/bushel of seed), and relied upon their vapor

action to permeate through the seed during storage; thus, if the seed was not

very evenly treated, it did not really matter

With the banning of the organo-mercury compounds, first in Sweden and

then in other countries, a search was on for nonmercurial seed treatments

This led to the development of seed treatment formulations of maneb, dexon,

captan and thiram, etc., as dry powders for the planter box applications, as

well as flowable formulations for the seed processor

In the 1970s, certain systemic seed treatment compounds such as Vitavax

were synthesized However, none of these compounds had the vapor action

property of the organo-mercury compounds and thus the resulting

formula-tions had to meet certain desirable properties Also, dual and even triple

ac-tive-ingredient seed treatment formulations began to appear which could

contain possibly two fungicides and an insecticide, or a fungicide and two

insecticides, such as AGROX D-L Plus, which contains captan, diazinon,

and lindane These formulations were developed in order to protect against a

variety of seed or soil-borne pathogens, as well as soil insects

Desirable Properties of a Seed Treatment

The formulation chemist must consider the following desirable properties

of a seed treatment formulation:

1 The product must be toxic to pathogens or insects or to both

2 The product must be noninjurious to seed, even at two and four times

the recommended application rates

3 The product should be noncorrosive to equipment

4 The product should have good chemical and physical stability when

stored for at least three years under typical warehouse conditions It is

recom-mended that, during the development stage, samples be stored in various

warehouses and recalled at certain intervals for analysis of the active

ingredi-ents, as well as examination for physical incompatibilities

5 The product should be packaged in a suitable and convenient manner,

so that it is easy to handle and will not create a dust problem when used

ac-cording to label directions

6 The product should exhibit good adhesion and retention properties

Results of one test procedure used are given in Table 1

7 A seed treatment should be colored in such a manner that treated seed

can be clearly distinguished from untreated and, if the treated seed is mixed

with untreated, the contamination can be readily seen by visual inspection

The aforementioned properties deal only with the desirable characteristics

of the product itself The formulation chemist must also then consider the

way in which the product will be used in the field This includes not only the

Processor Equipment

% Lindane % Retained L09 70.3 L21 78.1 1.49 96.1

Planting Equipment

% Lindane % Retained 0.95 61.3 1.05 67.7 1.48 95.5

"Percent retention of product is based on the lindane analysis of the treated seed

equipment used by the seed processor, but also the appHcation equipment

that will be used by the grower and, of course, the type of seed that is to be

treated

Seed Treatment Equipment

Over the years, there have been numerous developments in seed treating

machinery which can be used by the seed processor as well as by the grower to

plant seed

Process treating equipment ranges from dipper cup type treaters, which

dispense small volumes of liquid treatments onto a known trip weight of seed,

to treaters which dispense a known volume through a mist spray system

Treating equipment used for corn is different from the type of equipment

used for small-grain cereals such as wheat and barley, as the seed treatment

products are usually diluted with water prior to treating seed corn for storage

The formulation chemist should be acquainted with all types of equipment,

because the product he is developing will eventually be used through certain

equipment by the grower or the processor or both Therefore the following

aspects of the seed treating must be considered:

• The seed being treated must receive the correct amount of treatment

and, hence, the product should be developed to flow smoothly and rapidly

through the processor's equipment

An example of the above would be the development of a flowable seed

treat-ment which, due to a somewhat high viscosity, will allow the processor to treat

only 2400 kg of wheat per hour at the correct treatment rate

The equipment is designed to treat at a rate of 6000 kg/h, and a

competi-tive product treats at 5100 kg/h It is obvious that the formulation chemist

must develop a product which can be used satisfactorily and meets or is better

than the competitive product

• The treatment must adhere strongly enough on the seeds to avoid losses

during the handling from the processor treatment stage to the planting

pro-cess

1 8 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

The data in Table 1 illustrate the results obtained during the development

of a seed treatment for Canola

The seed treatment was guaranteed to contain 50% lindane and 10%

cap-tan, and the application rate was 775 g/25 kg of Canola seed After the seed

was treated, samples were taken from the processor equipment and planting

equipment and analyzed for lindane by gas chromatography If the seed

re-tained 100% of the product, the lindane content would have been 1.55% by

weight The percentage retention of the product was calculated on this basis

Needless to say Formulation No 3453-C was eventually registered for sale

• The treated seed will not clog planting equipment and cause mechanical

problems at planting time This is most important in the development of

planter box treatments Hence, the planting rates of seed treated with trial

formulations should be checked through various types of equipment, first in

the laboratory and then in the field

Table 2 outlines data obtained in the development of a new corn seed

treat-ment using a laboratory plate planter The seed was placed in the hopper and

treated according to product directions The treated seed then fell through a

planter plate and was held captive by plastic cups which revolved on a belt

device, using an electric motor set at 8 km/h At any given time, the

equip-ment could be turned off and the seeds in the cups counted

Field results confirmed the laboratory findings that Formulation Nos

3169-A and B built up on the plates and eventually clogged the seeding

mech-anism Formulation No 3169-D was found to be satisfactory and eventually

was registered for sale

Certain other factors should be considered when developing a seed

treat-ment formulation They are briefly outlined below:

1 Climatic conditions—temperature, humidity, etc In some regions,

seed is treated in the winter at temperatures of —10 to — 25°C and therefore

cold stability must be considered

2 The chemical stability of the active ingredients on the seed over a

stor-TABLE 2—Flowability evaluation of Product 3169 using an

International Harvester plant plate tester

No

3169-A 3169-B 3169-C 3169-D

age period prior to planting should be considered, because seed sometimes is

treated several months in advance of planting

3 Cosmetic effect—very important because the grower does not want a

dusty product but does require good seed coverage and color; in fact,

colora-tion of the product should be ideally the same from batch to batch Growers

and seed processors can be quite critical of batches of the same product which

differ in shades of color

Protocol

From the above data, the following protocol has been developed for the

research and development of seed treatment formulations

Protocol—Phase I

Phase I is basically the decision-making phase where compounds are

inves-tigated and acquired for the formulation development process The items

dealt with at this stage are:

(a) A literature search on active ingredients which are active against soil

or seed-borne pathogens and/or soil insects

(Z>) A review of available technical data, physical and chemical, on the

respective compound(s)

(c) A decision on the types of formulations which can possibly be

pro-duced

{d) The issuing of tentative armchair formulations for costing purposes

(e) If {d) appears acceptable, acquisition of formulation ingredients

(/) The preparation of prototype formulations for initial screening and

phytotoxicity studies

ig) Finally, further costing of the prototype formulations to see whether

they are still economical

Protocol—Phase II

Phase II can be divided into two sections: (1) Chemical and Physical

Evalu-ation, and (2) Biological Evaluation of the Trial Formulations

Chemical and Physical Evaluation:

1 Specimens are analyzed for active ingredients prior to commencing the

program

2 Storage tests are initiated on all promising formulations at room

tem-perature and under accelerated aging conditions The specimens held at

room temperature are analyzed after three months, six months, one year, and

two years from date of placing in storage; the accelerated aging specimens are

stored at 37.5°C, and sometimes 50°C as well, for three months These

speci-20 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

mens are then analyzed after six weeks and three months from date of placing

in the heated chambers

3 The seed is treated with the recommended rate of product, at twice and

sometimes four times the rates, and then analyzed for adhesion and retention

properties of the product Formulation refinements should be made if the

above properties are not considered acceptable

4 The treated seed is analyzed for active ingredients and samples of the

treated seed are placed under field storage conditions for one year Samples of

the seed should be removed at three-month intervals for chemical stability

analysis and germination testing (see Biological Evaluation section below)

5 As soon as possible, evaluation of containers for packaging of the

prod-uct should be initiated by placing the most promising formulations in the

con-tainers which will eventually be used for marketing the product These

sam-ples should be stored under accelerated aging conditions for three months as

well as for one and two years at ambient temperatures

Biological Evaluation—ki the same time as the above tests are being

initi-ated, the following biological tests should be commenced:

1 The treated seed, at various application rates, is subjected to petri-dish

germination tests and, if the results are acceptable, then further germination

tests on soil are undertaken

2 These germination tests are repeated at three-monthly intervals on the

stored treated seeds from the chemical evaluation program

3 As soon as the weather permits, field trials for efficacy and residue data

should commence Data, such as plant stand, phytotoxicity observations,

dis-ease, and insect counts and yields should be collected Samples of the crop,

and possibly soil, should be taken for residue analyses

An example of test data which can be obtained from field plot trials is

out-lined in Table 3

TABLE 3—Evaluation of Compound No 3646 liquid seed treatment

formulations for Winolta-variety wheat

Treatment 3646-A 3646-A 3646-B 3646-B 3646-C 3646-C Check

Rate"

0.075 0.150 0.075 0.150 0.075 0.150 untreated

Germination' Lab Petri Dish

"Grams active ingredient per kilogram of seed

'Average number of seeds germinated from 4 reps (50 seeds/rep)

'Plant vigor rating: 1 = poor; 10 = excellent

Protocol—Phase III

Phase III is as follows:

1 Evaluate the product through the appropriate processor and planting

equipment

2 Carry out more extensive field evaluation through company and grower

trials, keeping in mind that research permits are usually required for these

trials

3 Carry out a final costing and eventually issue formulation procedures to

the production department for pilot-scale manufacture

4 Initiate plans to develop larger-scale manufacture as the market

ex-pands

Formulation Development

Seed treatment formulations are not the easiest of pesticide products to

develop The simple blending and milling of active ingredients with such

in-erts as talcs or clays or both, plus the addition of dye for coloration purposes

for powder products, can lead to field equipment problems The simple

dis-solving of an active ingredient in a solvent, plus dye addition, can cause

pene-tration of an active ingredient into the seed, which then could cause

germina-tion and even residue problems Even the addigermina-tion of small amounts of oils or

stickers to a power formulation, to prevent dustiness, can have side effects

Conclusions

1 Formulation 3646-C was found to be phytotoxic, both in the soil and in

the petri-dish test

2 Germination and vigor of seed treated with 3646-B was superior to that

of seed treated with 3646-A and 3646-C at the 0.150 g active ingredient per

kilogram of seed

3 Formulation 3646-B was selected as the candidate formulation for

fur-ther field trials to establish the efficacy of the product

Therefore the chemist developing seed treatments must be extremely

care-ful in the ingredients he chooses for the development of each product He

must be patient, willing to put up with certain frustrations, and spend

consid-erable time and effort on the development program

Finally, Ref 3 is recommended as an excellent source of material on the

subject of seed treatment

Acknowledgments

The author wishes to thank Mr D B Smith for the use of the laboratory

and field germination data included herein

22 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

Referances

[1] Martin, H., The Scientific Principles of Crop Protection, Edward Arnold, London, 1959

[2] Mossfall, J G., Fungicides and Their Action, Waltham, MA, 1945

[3] Seed Treatment, K A Jeffs, Ed., Collaborative International Pesticides Analytical Council

Ltd., 5C Andrew's Lodge, Southdown Road, Harpendon, Hertfordshire, England, 1978

Evaluation of Factors Affecting Tank

Mix Compatibility of Pesticide

Combinations

REFERENCE: Brenner, W E., Brown, L J., and Machado, I E., "Evaluation of

Fac-tors Affecting Tanlc Mix Compatibility of Pesticide Combinations," Pesticide

Formula-tions and Application Systems: Fourth Symposium, ASTM STP875, T M Kaneko and

L D Spicer, Eds., American Society for Testing and Materials, Philadelphia, 1985, pp

24-36

ABSTRACT: Laboratory tank mix compatibility testing presents the challenge of

predict-ing the ultimate physical fate of mixtures under a large variety of often poorly known field

use conditions Most procedures, as dictated by practical necessity, involve only a few test

conditions, are easy to perform, and utilize common laboratory equipment By reason of

their simplicity, however, these tests may fail to adequately mimic, hold fixed, or consider

many of the field variables which may influence compatibility

Studies were conducted with two formulations of each of two pesticides to explore the

effects of some of the variables generally known or perceived to affect formulation

perfor-mance and physical compatibility Fractional factorial experimental designs were

con-ducted in stages to study the effects and interactions of water hardness, temperature,

co-pesticide ratio, order of addition, degree of agitation, residence time of the mix in the

tank, and dilution rate For one of the formulation pairs multiple regression and analysis

of variance were used to construct a model which was able to adequately predict the

fail-ure or success of experiments not yet performed The results indicate that all these factors

can affect tank mix compatibility Complex interactions between the factors were

ob-served The effects and interactions of the factors appeared to vary both qualitatively and

quantitatively from the other formulation pairs, indicating that the major effects and

crit-ical ranges of factors are different for different tank mixes These results indicate the

types of difficulties which can be expected to be encountered in devising simple

standard-ized tests for tank mix compatibility

KEYWORDS: pesticide, formulation, physical/chemical properties, tank mix,

compati-bility, dilution rate, temperature, shear rate, ratio, addition order, agitation

Selectivity for control of a pest or range of pests is an increasingly common

attribute of modern-day pesticides This selectivity, although desirable from

' Shell Development Company, Biological Sciences Research Center, Modesto, CA 95352

24 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

many respects, often presents the problem of dealing with a spectrum of pests

(insects, weeds, etc.) which is wider than that controlled by a single pesticide

Consequently, and driven by economic considerations, mixing of two or more

complementary materials has become common practice Occasionally,

com-bination formulations are available for a given task More often, however, the

mixing is performed at the user level in the spray tank Obviously, the

co-pesticides must be chemically compatible In addition, the co-co-pesticides'

for-mulations must also be physically compatible so that application is not

im-paired

Laboratory testing of physical tank mix compatibility presents the

chal-lenge of predicting the ultimate fate of mixtures under a large variety of often

poorly known and sometimes practically uncontrollable field use conditions

Most procedures, as dictated by practical necessity, involve only a few test

conditions, are relatively easy to perform, and utilize common laboratory

equipment By virtue of their simplicity, however, these tests may fail to

ade-quately mimic, hold fixed, or ignore many of the field variables which may

influence compatibility A large number of variables are known or perceived

to affect compatibility, including nature of the spray carrier (water hardness,

pH, fertilizer type, etc.), temperature, order of addition of the materials to

the tank, degree of agitation, residence time of the mixture in the tank,

co-pesticide ratio, final spray (dilution) rate, aeration/foaming induction,

agita-tion shut-off/quiescence/restart, rate/speed of addiagita-tion of mix components,

etc The present study was conducted to investigate the effects of some of

these variables on the compatibility of combinations of two formulations of

each of two different pesticides, tested by a relatively simple laboratory

method The ultimate aim was to discover a relatively small set of

experimen-tal conditions which could be used to characterize the compatibility of a range

of similar formulation tank mixes

Test Procedures and Materials

Test procedures involved addition of mix components into 250-mL mixing

cylinders followed by transfer into 0.5 L (1 pt) bottles and agitation on a

bench-top reciprocating shaker for a prescribed period of time.^ The mixtures

were then poured through U.S Standard 50-mesh (300 /xm opening) screens

and given a failure (compatibility/incompatibility) rating on a scale from 0 to

10 The scale was based on increasing degree of screen blockage and amount

of material retained on the screen, visually assessed by an experienced

ob-server Failure ratings of 0 to 2 would generally be considered acceptable,

while ratings of 8 to 10 would be clearly unacceptable While the definition of

physical compatibility/incompatibility may be the subject of considerable

de-^ Shell Development Company Test Method MMS-C-521-2, Dec 1981; available upon request

from the authors

bate, and this assessment basis may be viewed as over simplistic, it was

deemed to serve the purpose of the test From a pragmatic point of view, the

mixtures' ability to clear the screen indicates they are "sprayable" and

there-fore "compatible." Conversely, blockage of this widely used size screen

indi-cates potential application problems

Two formulations, each of distinct composition, of two complementary

pesticides, A and B, were selected for this study.-' Formulations of A (Al, A2)

were concentrated suspensions ("flowables") and those of B (Bl, B2) were

emulsible concentrates (ECs) Water was used throughout the study as the

spray carrier

Experimental Procedure and Discussion

Of the many potential experimental variables, seven were chosen for study:

water hardness, temperature, pesticide ratio, order of addition of the

co-pesticides to the water, degree of agitation/shear, residence time of the

mix-ture in the vessel, and spray (dilution) rate Two levels were selected for the

first six variables and three for dilution rate Water hardnesses tested were 35

and 900 ppm as calcium carbonate Test temperatures were 4 ± 1°C (40 ±

2°F), conducted in an environmental chamber, and 22 ± 1°C (72 ± 2°F),

room temperature (RT) Two different co-pesticide ratios, representing

po-tential field uses, were chosen and are designated by Rl and R2 Order of

addition is denoted by, for example, A l / B l , indicating formulation Al was

added first, followed by B l Degrees of agitation, designated "high" or

"low," represent shaking on a bench-top Eberbach reciprocating shaker with

a 3.8 cm (1.5 in.) stroke at 270 and 135 cycles/min, respectively Residence

times chosen were 1 and 6 h Dilution rates were equivalent to 19, 47, and 94

L/ha ( 2 , 5 , and 10 gal/acre)

For any given pair of co-pesticide formulations, the testing of 192 (3 X

2^ = 192) combinations of experimental conditions would be required to

de-termine all possible interactions between the seven variables at the chosen

levels Since this was considered an inordinate number of tests, a fractional

factorial experimental design was conducted in stages The first stage,

con-ducted with formulations Al and Bl, consisted of a Vs replicate (8 of the 2*

possible combinations of the two-level factors at each of the 3 dilution rates,

or 24 experimental points) of the complete factorial design The 24

experi-mental combinations were performed in duplicate and in random order so as

to minimize any possible temporal changes and to provide a true estimate of

the experimental error No temporal changes were observed throughout the

conduct of these experiments The first stage experiment was designed to

screen whether only main (single variable) effects or additional interactions

' Identity of the pesticides is withheld for proprietary reasons The ensuing discussion and

con-clusions are not believed to be affected

2 6 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

existed Upon completion of these tests, it was noted that water hardness had

a highly significant effect Tests in 35 ppm water consistently resulted in high

(8 to 10) failure ratings In 900 ppm water, results were scattered (although

reproducibly so) throughout the rating scale Statistical analysis of the 900

ppm water data about a "main effects only" model gave an error term (all

interactions lumped together) which was too large to be attributable to

exper-imental error, particularly in light of the excellent reproducibility observed

This indicated that additional tests were needed to qualify the interactions

which must be present but were not estimable because of the fractional

repli-cation At this time, further testing in 35 ppm water was deemed useless for

the purpose of the study and was consequently discontinued Nonetheless, the

overwhelming effect on this co-pesticide formulation pair was duly recorded

for comparison with other pairs

With the elimination of water hardness as a study variable (all subsequent

tests with the A l / B l pair were conducted in 900 ppm water), the number of

combinations required to determine all interactions was reduced to 96 The

next stage in the study involved completion of a 48-point experiment (1/2

replicate of the 3 X 2 ^ complete factorial) designed so that all two-variable

interactions would be estimable, provided three-way and higher order

inter-actions were negligible Predictions for the 48 combinations not tested could

then be made if the assumption proved correct On completion, the

second-stage experiment revealed that a main effect plus the two-variable interaction

model still had too large an error term (although significantly lower than that

of the first stage) and thus indicated the probable presence of complex higher

order interactions for this formulation pair Additional experimental points

were tested and compared with the predictions of increasingly complex

models in order to revise and improve the predictive capability Upon

comple-tion of 77 experimental points, a 22-term model had been constructed which

was consistently predicting correctly the outcome of experimental points not

yet conducted The scatter of the data about this model had a standard

devia-tion of ± 1.9 failure rating units Using this model, it was felt that the

remain-ing 19 experimental combinations could be calculated, allowremain-ing for the

devel-opment of a final model equation which included all significant interactions

The model equation permits the separation of main effects and interactions

of factors Single-variable effects are shown in Fig 1 For dilution rate, each

point represents the mean of 32 combinations, while for all other variables,

each point represents the mean of 48 At this juncture, it should be noted that

the points are connected only for ease of interpretation purposes and not to

signify expected results within the variable ranges By themselves, these

graphs would indicate for the particular variable setting chosen that, on the

average, agitation time and degree, dilution rate and co-pesticide ratio had

the most effect, while temperature and order of addition had practically no

effect When interactions are examined, however, the complexity of effects

becomes more apparent Examples of two-variable interactions are shown in

Fig 2 It is of particular interest to note the interaction between temperature

and order of addition, both of which appeared to show insignificant effects

when viewed as single variables On the average, now, the failure rating is

higher for order of addition B l / A l at 4°C but lower at 22°C Examples of

three-way interactions are shown as pairs of graphs in Fig 3 By themselves,

each graph in a pair shows, qualitatively, the same two-factor interaction

The quantitative differences between the two graphs demonstrate the

interac-tion of the third variable For example, in the temperature X co-pesticide

ratio X order of addition pair, each graph shows an interaction between

tem-perature and ratio for a given order of addition, but the failure ratings

in-crease for one order of addition and dein-crease for the other, demonstrating the

third-factor interaction It is also of interest to compare this three-variable

interaction with the two-way interaction between temperature and order of

addition previously discussed The reversal of the temperature X order of

addition effect observed in Fig 2 can be seen to be more pronounced for ratio

Rl than for R2

A graphical example of four-variable interactions is given in Fig 4 By

themselves, all four graphs show two-way interactions between temperature

and co-pesticide ratio for a given agitation rate and time Comparisons of

graphs (a) and (b) or (c) and (d) adds the time factor interaction; comparison

of (a) and (c) or (b) and (d) adds degree of agitation as an interacting factor

Higher order (five and all six) variable interactions were fortunately negligible

relative to lower order interactions

Although a ranking of order of importance for the single variables and all

interactions is available from the analysis of variance table, such a ranking

must be viewed with caution in that only two arbitrary levels were chosen for

five of the variables and three for the sixth This point is illustrated by Fig 5,

where experimental data are compared for fit to the mathematical model

Within the test boundaries, the actual and predicted data (calculated from

the model) show an adequate fit, with 59 of 77 data points (77%) within ± 2

rating units of ideal correlation, 74 (96%) within ± 3 units, and all 77 points

within + 4 Although only 27 points are shown on the graph, they represent

the 77 observations, with many having the same predicted/actual ratings A

few tests were conducted at a 188 L/ha (20 gal/acre) dilution rate but with all

other factors within the original test boundaries These points display a much

poorer correlation, indicating that differences in main effects and/or

interac-tions can be expected as the boundaries are changed

The ultimate objective of this study was to discover if the results of one

formulation pair could be used to predict, at least qualitatively, the important

factors affecting and test results of a similar formulation pair To fulfill that

purpose, the same first-stage set of experiments (24 points) conducted with

formulations Al and Bl were also conducted with formulation pairs A1/B2

2 8 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

3

I

/ / / /

4

ONl-LVa^ 3 i ^ d n - ] l V ^ N V ^ t ^

30 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

M

/ \ /

CO r - t o lO " + TO M

3 2 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM

DILUTION * CO-PESTICIDE RATIO * TEMPERATURE

1 0 | w

-19(2) 47(5) 94(10)

DILUTION RATE, I/ha (gal/ocrs)

DILUTION RATE, I/ha (gal/acre)

DILUTION * CO-PESTICIDE RATIO * ORDER OF ADDITION

47(5) 94(10) DILUTION RATE, l/hc (gol/ocre)

•

- — • *

• • 0

19(2) 47(5) DILUTION RATE l A o (gal/acre)

FIG, 3—Examples of three-variable interactions

and A2/B1 Examination of the pattern created by plotting the failure rating

for one formulation pair against that of the other pair (Fig 6) shows that

different effects and/or interactions exist for each pair Had the points fallen

within normal scatter from a discernable trend (e.g., a straight line) it would

have indicated similar variable/interaction effects, and cross-pair predictions