Supreme Court of Texas

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No. 20-0881

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Helena Chemical Company,

Petitioner,

v.

Robert Cox, et al., 

Respondents

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On Petition for Review from the

Court of Appeals for the Eleventh District of Texas

═══════════════════════════════════════

Argued October 26, 2022

JUSTICE BLACKLOCK delivered the opinion of the Court.

JUSTICE YOUNG did not participate in the decision.

The plaintiffs are farmers who claim that an aerial herbicide 

drifted onto their farms and damaged their cotton crops. The defendant 

is Helena Chemical Company, which oversaw the aerial application of 

herbicide that the farmers blame for the damage. The district court 

granted summary judgment for Helena, but the court of appeals 

reversed. This Court is now asked whether the evidence that Helena’s 

application of herbicide caused the plaintiffs’ injury raises the genuine 
2

issue of material fact required to survive summary judgment. As 

explained below, we agree with the district court that it does not. The 

court of appeals’ judgment is affirmed in part and reversed in part, and 

the summary judgment for Helena is reinstated.

I.

A.

The plaintiffs farm cotton in Mitchell County.1 Defendant Helena 

distributes an herbicide called Sendero, which is primarily used to kill 

mesquite trees. Sendero contains two active ingredients—clopyralid 

and aminopyralid. These ingredients are used in many other products, 

but their use in combination is apparently unique to Sendero.

The plaintiffs allege that Helena supervised an aerial application 

of Sendero over several non-contiguous parcels of the Spade Ranch, a 

large ranch spanning parts of Coke, Sterling, and Mitchell Counties. 

Two planes sprayed roughly 3,300 gallons of Sendero over several days 

in July 2015. The spray was released from eight to ten feet above the 

treetops. The plaintiffs allege that the herbicide drifted onto their 

properties and damaged cotton crops planted in 2015 and 2016.

The plaintiffs blame Helena for reduced crop yields in over 14,000 

acres of cotton fields scattered across hundreds of square miles of 

Mitchell County. These fields are located between 1.8 miles and 25 

miles from the places on the Spade Ranch where Helena sprayed 

Sendero. The precise locations of the allegedly affected fields are not 

1 The plaintiffs are Robert Cox, James Cox Trust, Cox Farms, Tanner 

Cox, Loren Rees, Tyson Price, Russell Erwin, David Stubblefield, Rushnell 

Farms, Brooks Wallis, Hoyle & Hoyle, and Jack Ainsworth.
3

entirely clear from the record, which contains only a high-altitude map 

showing color-coded parcels identifying most of the plaintiffs’ fields. The 

placement of the fields follows no discernable pattern. Some fields are 

bunched together, while some are isolated by many miles.

After Helena’s application of Sendero over the Spade Ranch, the 

plaintiffs complained of crop damage. Texas Department of Agriculture 

(TDA) inspector Cory Pence investigated the incident in July 2015. He 

concluded that the Spade Ranch application of Sendero was a possible 

cause of the plaintiffs’ crop damage. He claimed to find “markers” for 

both aminopyralid and clopyralid. He was unable, however, to identify 

a “consistent pattern” or “drift pattern” of crop damage over this large 

area. Pence conducted only a visual inspection, and TDA never 

conducted any laboratory tests for aminopyralid or clopyralid. When 

deposed, Pence could not explain the difference between markers for 

aminopyralid and clopyralid.

The plaintiffs allege that Sendero is highly toxic to cotton plants 

and should only be applied when the risk of drift onto nearby, sensitive 

areas is minimal. Warnings on Sendero’s label say as much, and Helena 

does not contend otherwise. The plaintiffs allege that weather 

conditions—including wind, temperature, and humidity—were such 

that Sendero should not have been sprayed on the days in question. 

They further allege that application of the herbicide at an 

inappropriately high altitude resulted in greater drift onto neighboring 

properties.

The plaintiffs harvested and sold what they could from their 2015 

crops. They gathered only limited evidence of the herbicide damage, 
4

either at the time they noticed it or at the time of harvest. Notably, 

many of the plaintiffs filed insurance claims attributing their crop losses 

to drought or other adverse weather. The record contains three 

photographs of allegedly damaged crops. These photos come from 

unidentified fields and were taken on unknown dates.2

B.

The plaintiffs sued Helena and other defendants in 2015 in 

Mitchell County. They sought recovery under various theories for the 

reduced cotton crop produced by their land in 2015 and 2016, as well as 

mental-anguish damages and punitive damages.

Helena filed several dispositive motions. The district court 

granted Helena’s motion for partial summary judgment as to mental 

anguish, gross negligence, and punitive damages. Helena also filed a 

no-evidence motion for summary judgment, arguing that no evidence 

supported the element of causation essential to recovery under all the

plaintiffs’ claims. Helena simultaneously filed a motion to strike the 

plaintiffs’ expert opinions on causation, arguing that the opinions were 

unreliable and therefore inadmissible. Helena further contended that 

even if the experts’ opinions were admitted, they would constitute no 

evidence of causation, requiring summary judgment for Helena.

2 Plaintiffs’ experts Ronald Halfmann and Tracey Carrillo, whose 

opinions are discussed below, attested that they had reviewed “hundreds” of 

photographs of crop damage in Mitchell County, but these photographs are not 

in the record, which is silent as to the dates, the precise locations, or any other 

specifics regarding the crop damage depicted in the photographs reviewed by 

the experts.
5

The plaintiffs retained five experts whose testimony bears on 

causation: Ronald Halfmann, Tracey Carrillo, Daylon Royal, Paul 

Rosenfeld, and Paul Ward. Their affidavits, expert reports, and 

deposition testimony are part of the record and were the focus of the 

no-evidence summary-judgment motion and the motion to strike.3 The 

experts did not visit the affected fields or collect cotton samples. They

relied on reports from TDA inspector Pence and from the plaintiffs, as 

well as on other available information.

Ronald Halfmann is a former inspector with the TDA. He 

identified himself as an expert “in agricultur[al] application of 

pesticides” with “extensive experience investigating pesticide drift.” He 

opined that Helena breached the standard of care for use of aerial 

herbicides, that weather conditions and faulty application techniques 

caused excessive drift, and that the Spade Ranch application of Sendero 

damaged 15,000 acres of cotton as claimed by the plaintiffs. He stated 

that Sendero can drift up to 20 miles under hazardous weather 

3 A separate group of plaintiffs sued Helena in Reagan County. The 

lawyers in that case and in this case agreed that certain expert affidavits and 

depositions could be used in both cases. Although they did not so argue in the 

district court, the plaintiffs now contend that this Rule 11 agreement restricted 

Helena’s right to challenge the reliability of the experts’ testimony. We 

disagree. We read the agreement as intended to eliminate needless duplication 

of discovery and to permit the use of the expert opinions insofar as they recite 

the experts’ “qualifications and experience,” the “methodology employed” by 

the experts, and the “scope and extent” of the opinions. We do not read the 

agreement as intended to waive Helena’s right to challenge the substance of 

the experts’ opinions as unreliable. The attorneys who executed the agreement 

did not argue in the district court that the agreement has the effect now 

claimed.
6

conditions and that, in his opinion, only a large application of herbicide 

would have caused the damage reported by the plaintiffs.

Tracey Carrillo is an agronomist and entomologist. He has many 

years of experience in cotton farming and herbicide drift. In his opinion, 

damage from Sendero occurred in all the plaintiffs’ fields. He based this 

opinion on the Sendero label, plant tissue samples that were tested for 

clopyralid and aminopyralid, observations from the farmers, the report 

of TDA investigator Pence, and other information. He explained that 

damage to cotton fields from Sendero is prolonged and substantial and 

that damage from aerial-drift events is widely known and accepted. He 

opined that crop damage in 2015, 2016, and 2017 was consistent with a 

large-scale application of Sendero. He concluded, based on his review of 

the evidence, including lab test results, that “there is no doubt that [the 

plaintiffs’] cotton was contaminated from spray drift of applications of 

Sendero conducted by [Helena].”

Daylon Royal is a crop-dusting pilot. He also addressed physical 

drift. He advised Carrillo that it was highly probable that Helena’s 

application of Sendero had caused the herbicide to drift onto the 

plaintiffs’ fields because of wind and temperature conditions at the time. 

He relied on a “rule of thumb” that as much as 50% of aerially applied 

pesticide drifts away from the targeted field.

Paul Rosenfeld is an environmental chemist who has studied the 

effect of Sendero on crops. He provided evidence that Sendero results in 

long-term damage to cotton fields. Based on Pence’s TDA report and 

other information, Rosenfeld concluded that Sendero drifted onto the 

plaintiffs’ farms and damaged their cotton crops. He testified that 
7

Helena’s 2015 Sendero application would remain in the soil and damage

the plaintiffs’ crops in 2016.

Paul Ward grew bean plants in soil samples taken from Mitchell 

County and compared them to samples grown in potting soil. He had no 

prior experience evaluating herbicide exposure and no experience with 

Sendero, clopyralid, or aminopyralid. He did not know whether any 

scientific studies confirmed that his methods were reliable to show what 

actually happens in cotton fields.

The district court held an extensive hearing on the motion to 

strike the expert testimony. It later granted the summary-judgment 

motion and the motion to strike and rendered judgment for Helena. The 

court of appeals reversed, in large part. 630 S.W.3d 234, 249 (Tex. 

App.—Eastland 2020). It reasoned:

Although Halfmann, Carrillo, and Rosenfeld could not 

specifically trace the purported drift of clopyralid from the 

Spade Ranch to Appellants’ cotton fields, they provided a 

reliable scientific basis for their opinions that Appellants’ 

cotton crops were damaged by a large-scale aerial 

application of clopyralid to the south of Appellants’ fields. 

Relying on Pence’s investigation and observations that 

Helena’s aerial application of Sendero, which was done in 

conditions that exacerbated drift, was the only such 

large-scale application at the relevant time and place, they 

concluded that the damage to Appellants’ cotton crops was 

caused by Helena. We see no analytical gap in such a 

conclusion. We sustain Appellants’ second issue as to 

Appellants’ expert witnesses with one exception: that 

exception being Royal’s attempt to offer an opinion that 

Sendero drifted from Helena’s application site to 

Appellants’ fields.

Id. at 243–44. Because it concluded that the experts’ evidence was 

reliable and therefore admissible, the court of appeals also concluded 
8

that there was evidence of causation sufficient to survive summary 

judgment. Id. at 244–45.

The court of appeals did, however, agree with Helena that it was 

entitled to partial summary judgment as to claims for mental anguish 

and punitive damages. The plaintiffs do not challenge the court of 

appeals’ affirmance of summary judgment in this regard. After 

affirming in part and reversing in part, the court of appeals remanded 

the case to the district court for further proceedings. Id. at 249. Helena 

petitioned for review in this Court, and we granted the petition.

II.

A.

A party may move for summary judgment, after adequate time 

for discovery, “on the ground that there is no evidence of one or more 

essential elements of a claim or defense on which an adverse party 

would have the burden of proof at trial.” TEX. R. CIV. P. 166a(i). The 

court must grant such a “no-evidence” motion unless the non-moving 

party responds with “evidence raising a genuine issue of material fact.” 

Id. Appellate courts review summary judgments de novo. Valence 

Operating Co. v. Dorsett, 164 S.W.3d 656, 661 (Tex. 2005). In so doing, 

we examine the evidence in the light most favorable to the non-moving 

party, indulging reasonable inferences and resolving doubts against the 

party seeking summary judgment. City of Keller v. Wilson, 168 S.W.3d 

802, 824 (Tex. 2005).

The issue before this Court is whether the plaintiffs’ evidence 

raised a genuine issue of material fact on causation, which is an 

essential element of all the plaintiffs’ claims on which they bear the 
9

burden of proof. To survive summary judgment, the plaintiffs’ causation 

evidence must raise a genuine fact issue as to whether it is more likely 

than not that Helena’s application of Sendero in July 2015 caused a 

reduced yield of cotton and therefore reduced income for the farmers.

The central inquiry—viewed either through the lens of a motion 

to strike the evidence or a summary-judgment motion—is whether the 

plaintiffs’ experts offered reliable evidence of causation. As for the 

motion to strike, “[a]dmission of expert testimony that does not meet the 

reliability requirement is an abuse of discretion.” Cooper Tire & Rubber 

Co. v. Mendez, 204 S.W.3d 797, 800 (Tex. 2006). As for the 

summary-judgment motion, if the expert’s opinion is not reliable, it is 

no evidence and will not defeat a no-evidence motion for summary 

judgment. Seger v. Yorkshire Ins. Co., 503 S.W.3d 388, 410 n.23 (Tex. 

2016) (“Unreliable expert testimony is legally no evidence.”); Merrell 

Dow Pharms., Inc. v. Havner, 953 S.W.2d 706, 713 (Tex. 1997) (“If the 

expert’s scientific testimony is not reliable, it is not evidence.”). To 

resolve this appeal, we will assume the experts’ opinions have been 

admitted, and we will ask whether these opinions are reliable evidence 

of causation sufficient to overcome Helena’s motion for summary 

judgment.

A witness may be qualified to testify as an expert based on his 

“knowledge, skill, experience, training, or education.” TEX. R. EVID. 702. 

Although an expert witness need not always be formally credentialed as 

a scientist, expert testimony on scientific matters—such as the aerial 

drift of herbicide particles or the effect of herbicide exposure on plants—

naturally must be “grounded ‘in the methods and procedures of science.’” 
10

E.I. du Pont de Nemours & Co. v. Robinson, 923 S.W.2d 549, 557 (Tex. 

1995) (quoting Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579, 590 

(1993)); see also Gammill v. Jack Williams Chevrolet, Inc., 972 S.W.2d 

713, 721–22 (Tex. 1998) (discussing reliability analysis for scientific 

opinion based on witness’s skill, experience, or training). Unreliable 

testimony, by contrast, includes that which “is no more than ‘subjective 

belief or unsupported speculation.’” Robinson, 923 S.W.2d at 557

(quoting Daubert, 509 U.S. at 590). “If the expert brings only his 

credentials and a subjective opinion, his testimony is fundamentally 

unsupported and therefore of no assistance to the jury.” Cooper Tire, 

204 S.W.3d at 801. The mere ipse dixit of the expert—that is, asking 

the jury to take the expert’s word for it because he is an expert—will not 

suffice. See City of San Antonio v. Pollock, 284 S.W.3d 809, 816 (Tex. 

2009). Instead, an expert’s conclusions must have a reliable basis other 

than the expert’s say-so. And “if no basis for the [expert] opinion is 

offered, or the basis offered provides no support, the opinion is merely a 

conclusory statement and cannot be considered probative evidence.” Id. 

at 818.

In determining the reliability of expert testimony, courts must 

consider not just whether the expert’s methods are grounded in science, 

but also whether the data to which the expert applies his methods are 

reliable. “If the foundational data underlying opinion testimony are 

unreliable, an expert will not be permitted to base an opinion on that 

data because any opinion drawn from that data is likewise unreliable.” 

Havner, 953 S.W.2d at 714. Moreover, “an expert’s testimony is 

unreliable even when the underlying data are sound if the expert draws 
11

conclusions from that data based on flawed methodology. A flaw in the 

expert’s reasoning from the data may render reliance on a study 

unreasonable and render the inferences drawn therefrom dubious.” Id. 

Likewise, “if an expert’s opinion is based on certain assumptions about 

the facts, we cannot disregard evidence showing those assumptions were 

unfounded.” City of Keller, 168 S.W.3d at 813.

We have also recognized that expert testimony is unreliable if 

“there is simply too great an analytical gap between the data and the 

opinion proffered.” Gammill, 972 S.W.2d at 727 (quoting Gen. Elec. Co. 

v. Joiner, 522 U.S. 136, 146 (1997)). “We are not required . . . to ignore 

fatal gaps in an expert’s analysis or assertions that are simply 

incorrect.” Volkswagen of Am., Inc. v. Ramirez, 159 S.W.3d 897, 912 

(Tex. 2005). “Analytical gaps may include circumstances in which the 

expert unreliably applies otherwise sound principles and methodologies, 

the expert’s opinion is based on assumed facts that vary materially from 

the facts in the record, or the expert’s opinion is based on tests or data 

that do not support the conclusions reached.” Gharda USA, Inc. v. 

Control Sols., Inc., 464 S.W.3d 338, 349 (Tex. 2015) (citations omitted).

Augmenting the above standards, our decision in Robinson 

identified six non-exclusive factors courts may consider in determining 

whether expert testimony is reliable:

1. the extent to which the theory has been or can be tested;

2. the extent to which the technique relies upon the 

subjective interpretation of the expert;

3. whether the theory has been subjected to peer review 

and/or publication;

4. the technique’s potential rate of error;
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5. whether the underlying theory or technique has been 

generally accepted as valid by the relevant scientific 

community; and

6. the non-judicial uses which have been made of the 

theory or technique.

923 S.W.2d at 557. The “Robinson factors” are not always determinative 

when assessing an expert’s reliability, but even when they are not, the 

court must be provided with some way of assessing the reliability of 

objected-to expert testimony, apart from the expert’s credentials and 

say-so. Gammill, 972 S.W.2d at 726.4

B.

“[T]he ultimate issue . . . in a toxic tort case . . . is always specific 

causation—whether the defendant’s product caused the plaintiff’s 

4 Amicus curiae High Plains Wine & Food Foundation, unlike the 

parties, relies heavily on this Court’s decision in Pitchfork Land & Cattle Co. 

v. King, 346 S.W.2d 598 (Tex. 1961). Pitchfork Land assessed expert testimony 

in an aerial-drift case, but unlike the amicus, we do not understand Pitchfork 

Land to require a unique “standard for measuring the legal sufficiency of 

causation evidence in crop-dusting cases.” Rather than cordoning off 

crop-dusting cases into a special category, we should read Pitchfork Land in 

conjunction with our more recent caselaw on expert testimony on scientific 

matters in toxic-tort cases, in which we have established more searching

standards for evaluating the reliability of any such testimony. Robinson, in 

particular, was a landmark 1995 case that largely adopted the federal 

standards articulated in Daubert and signaled the beginning of this Court’s 

modern approach to expert testimony in cases alleging exposure to toxic 

substances. Robinson involved facts remarkably similar to those here; the 

allegation was crop damage caused by fungicide. It would be quite odd for one 

approach to the reliability of expert causation evidence to apply in a case about 

crop damage from herbicides, but another approach to apply in a case about 

crop damage from fungicides. The reality is that cases like Daubert and 

Robinson marked an important development in the courts’ approach to these 

matters, which has since become settled law. It should be unremarkable to 

observe that many earlier cases, including a 1961 spray-drift case, do not fully 

reflect the approach to expert testimony required by Robinson and later cases.
13

injury.” Bostic v. Georgia-Pacific Corp., 439 S.W.3d 332, 351 (Tex. 2014). 

It is important to emphasize at the outset that the plaintiffs’ injury here 

is not “damage” to cotton plants, such as wilted leaves. Instead, the 

injury for which the plaintiffs seek recovery is a financial one—

decreased revenue from a reduced yield of cotton at harvest. It is 

therefore not enough for the plaintiffs to show that drifting herbicides 

reached their plants and “damaged” them in some way. Instead, they 

must show that Helena’s application of Sendero caused their plants to 

yield less cotton at harvest. They need not prove this at the 

summary-judgment stage, however. To survive Helena’s motion for 

summary judgment, the plaintiffs must proffer some evidence creating 

a genuine fact issue as to whether Helena’s application of Sendero 

caused the reduced crop yield. Draughon v. Johnson, 631 S.W.3d 81, 88 

(Tex. 2021).

The plaintiffs suggest that, apart from the expert testimony on 

which they rely, the lay opinions of the farmers themselves about the 

source of their crop failure can provide evidence of causation sufficient 

to survive summary judgment. In the context of this case, we disagree. 

“Expert testimony is required when an issue involves matters beyond 

jurors’ common understanding.” Mack Trucks, Inc. v. Tamez, 206 S.W.3d 

572, 583 (Tex. 2006); accord Gharda, 464 S.W.3d at 348. Determining 

whether a particular application of aerial herbicide substantially 

contributed to the failure of crops miles away requires knowledge and 

analysis of scientific matters beyond the competence of laymen.5 It goes 

5 See, e.g., Cerny v. Marathon Oil Corp., 480 S.W.3d 612, 620 (Tex. 

App.—San Antonio 2015, pet. denied) (stating that the requirement of expert 
14

without saying that plants, like all living things, become sickly or die for 

any number of natural and man-made reasons. And the expected aerial 

migration of herbicidal particles over vast distances due to weather 

conditions and spray techniques is plainly not a matter with which 

laymen are generally familiar. The plaintiffs were not offered as expert 

witnesses, and their lay opinions, standing alone, are insufficient to 

survive summary judgment.

As another initial matter, Helena argues that the required 

evidentiary showing of toxic exposure at a sufficient dose must be made 

for each “field” for which the plaintiffs seek recovery. According to 

Helena, “the term ‘field’ is used by the [U.S. Department of 

Agriculture’s] Farm Services Agency to designate the smallest unit of 

land for agricultural production.” Helena asks us to require discrete 

proof of causation as to each such “field” at the summary-judgment 

stage. Although the U.S.D.A.’s field designations provide a convenient 

way to categorize vast swaths of farmland, we cannot say that as a 

matter of law every plaintiff in a crop-loss case must proffer field-byfield proof using the U.S.D.A.’s field boundaries. To be sure, proof of 

toxic exposure at one spot on a farmer’s land is not proof of exposure 

throughout all of the farmer’s land. The plaintiff must show causation 

testimony is “obvious” where the “claims arise out of alleged emissions and 

migration of hazardous substances”); Foust v. Estate of Walters, 21 S.W.3d 495, 

505 (Tex. App.—San Antonio 2000, pet. denied) (“A negligence claim against 

an aerial applicator [of herbicide] must be established with expert testimony.”); 

Hager v. Romines, 913 S.W.2d 733, 734–35 (Tex. App.—Fort Worth 1995, no 

writ) (“We find that the standard of care in the aerial application of herbicide, 

as well as the violation of such standard, must be established by expert 

testimony.”).
15

for the entire area for which he seeks recovery, and using the U.S.D.A’s 

field designations may be a useful way to do so. But how a plaintiff goes 

about making that proof—or how a defendant goes about opposing it—

need not in every case invoke the field boundaries defined by the federal 

government.

C.

In a toxic-tort case alleging human exposure to harmful 

substances, the “minimal facts necessary to demonstrate specific 

causation” include “[s]cientific knowledge of the harmful level of 

exposure to a chemical, plus knowledge that the plaintiff was exposed to 

such quantities.” Builder Servs. Grp., Inc. v. Taylor, No. 03-18-00710-

CV, 2020 WL 5608484, at *6 (Tex. App.—Austin Sept. 17, 2020, pet. 

denied); see also Robinson, 923 S.W.2d at 557. What is true of injured 

plaintiffs in a toxic-exposure case is also true of injured crops in an 

herbicide-drift case. There must be reliable evidence that the failed 

crops for which recovery is sought were more likely than not (1) exposed 

to the harmful chemical, (2) at levels of exposure sufficient to cause the 

lost yields alleged. In addition, there must be reliable evidence ruling 

out other plausible alternative causes of the lost yields. Bostic, 439 

S.W.3d at 350; Havner, 953 S.W.2d at 720. Without some scientifically 

reliable evidence of these facts, the evidence of causation offered does 

not rise above subjective belief and will not survive a no-evidence motion 

for summary judgment. Robinson, 923 S.W.2d at 557.

We turn first to whether the plaintiffs’ evidence that their crops 

were exposed to Helena’s Sendero was sufficient to survive summary

judgment. Although the “field-by-field” proof demanded by Helena is 
16

not required, the plaintiffs must nevertheless come forward with 

reliable evidence of causation for any area for which they seek recovery. 

One obvious way to begin to show toxic contamination over a widespread 

area in such a case would be laboratory test results from spots 

throughout the allegedly affected area, coupled with reliable evidence 

that the tested areas are representative of the whole area for which 

damage is claimed. Yet rather than proffer lab testing confirming the 

presence of Sendero in representative areas, the plaintiffs offer only 

three positive lab results indicating the presence of clopyralid at 

identifiable locations. Three or four other tests indicated the presence 

of clopyralid at unknown locations within the allegedly damaged 

acreage.

No test indicated the presence of aminopyralid, the other active 

ingredient in Sendero. The plaintiffs’ experts acknowledged that 

herbicides other than Sendero contain clopyralid. Thus, the laboratory 

tests do not establish the presence of Sendero—as opposed to other 

herbicides—anywhere in the plaintiffs’ fields. Nevertheless, the 

plaintiffs’ experts also stated that aminopyralid often does not show up 

in laboratory testing because it is present in such small quantities. 

Deficiencies in aminopyralid testing are a matter within the expertise 

of Halfmann and Carrillo, and their opinions in this regard qualify as 

some evidence, at the summary-judgment stage, that (1) lab tests 

indicating positive results for clopyralid can indicate the presence of 

Sendero, and (2) lab testing will not necessarily distinguish Sendero 

from other herbicides.
17

The problem with the plaintiffs’ lab-testing evidence, however, is 

that their witnesses offered no reliable way to extrapolate from the small 

number of positive lab tests any conclusion at all about the presence of 

clopyralid—much less Sendero6—in the rest of the vast and scattered 

acreage for which recovery is sought. Even if the lab results are some 

evidence indicating Sendero’s presence in the areas with positive test 

results, they are no evidence that Sendero was present anywhere else.7

This is not to say that the plaintiffs needed to test every field in 

order to survive summary judgment. But they do need to show, using 

reliable methodology, that the acreage for which they actually have the 

kind of hard scientific data our cases typically require is representative 

6 TDA inspector Pence testified that he found “markers” for clopyralid 

and aminopyralid in the plaintiffs’ fields, and it appears the plaintiffs’ experts 

may have relied on this statement in concluding that Sendero was present. 

But Pence could not explain, at his deposition, what damage to a plant is a 

“marker” of aminopyralid, as opposed to other herbicides. And none of the 

plaintiffs’ experts—who relied heavily on pictures of the plants and reports 

from visual inspections by the farmers—provided an additional basis for 

concluding that the plants exhibited damage from Sendero, as opposed to other 

products. Carrillo testified that a visual inspection, even by an agronomist like 

himself, cannot distinguish between cotton plants exposed to Sendero and 

plants exposed to products containing only clopyralid or other herbicides. 

Plaintiffs’ experts Ward, Rosenfeld, and Halfmann agreed. Helena offered 

unrebutted evidence that clopyralid is found in numerous herbicides, including 

many herbicides used more commonly in the area during the summer months 

than Sendero. Halfmann confirmed that herbicidal treatment of mesquite by 

multiple land owners would likely occur during the summer.

7 As for the sites that tested positive for clopyralid, the causation 

evidence is insufficient to survive summary judgment for the reasons explained 

in Parts II.D and II.E, even if the positive clopyralid test is some evidence of 

Sendero’s presence at these sites.
18

of the larger area for which they seek recovery.8 They could do so, 

perhaps, by showing that the location of the positive clopyralid tests 

relative to the aerial Sendero application are such that the herbicide 

must have drifted through other, untested areas before reaching the 

tested area. They did not attempt to do this. Nor have they made any 

other effort to demonstrate with reliable methodology that positive lab 

results in a few places are indicative of the wider presence of clopyralid 

throughout the affected area.

To help fill the gap in testing data, the plaintiffs could have 

proffered a recognized model of the herbicide’s drift through the air onto 

the allegedly affected properties. Such evidence could provide a reliable 

indication that Helena’s product actually reached the allegedly damaged 

areas. The plaintiffs’ experts did not attempt to do this, however. They 

acknowledged that scientific models of aerial drift exist, but they did not 

employ these models or make any effort to recreate the aerial drift that 

would have occurred from the Spade Ranch given the weather conditions 

on July 1–4, 2015. They acknowledged that aerial drift typically occurs 

in a predictable pattern, in which fields closer to the source exhibit more 

8 See Plunkett v. Conn. Gen. Life Ins. Co., 285 S.W.3d 106, 115–17 (Tex. 

App.—Dallas 2009, pet. denied) (affirming no-evidence summary judgment 

where expert relied on positive mold test of furniture from one unit of a 

241-unit apartment complex, purported to extrapolate that test to “all property 

from all units,” and failed to provide “empirical evidence or methodology” 

explaining the validity of the extrapolation); Purina Mills, Inc., v. Odell, 948 

S.W.2d 927, 934, 937 (Tex. App.—Texarkana 1997, pet. denied) (holding that 

expert testimony was insufficient where plaintiff claimed 200 cattle were 

injured by defendant’s feed due to metal contamination, only two or three cattle 

were diagnosed with “hardware disease,” and experts had failed to conduct “a 

methodological or technical study of all the cattle or representative samples of 

the feed”).
19

damage than those farther away. And they acknowledged that the 

scattered pattern of steady damage in this case does not fit the usual 

aerial-drift model. Yet the only analysis provided of the drift pattern is 

that there was a heavy south wind on the days in question and the 

affected fields are north of the Spade Ranch.9 This observation certainly 

indicates the likelihood that some Sendero floated in the general

direction of the plaintiffs’ fields, but it is no evidence of causation 

because it amounts to no more than speculation that Sendero actually 

landed on these particular, scattered fields in a concentration sufficient 

to cause the crop damage and attendant loss of yield alleged.

The only testimony offered about aerial-drift patterns was 

inconclusive or speculative. Carrillo stated that there was no 

discernable pattern of harm to the damaged crops that would be “a 

common characteristic of physical drift.” Halfmann similarly testified 

that the “patchiness of the damage” in this case could not 

“scientifically . . . be explained by anyone” under a theory of drift 

patterns or a drift mechanism, and that the observed “sporadic effects” 

were “unexplainable.” The experts essentially expressed the view that 

aerial drift must have occurred here because of the widespread damage 

alleged—even though the damage pattern was not consistent with 

typical drift patterns. But their conclusions in this regard lack a reliable 

foundation grounded in science and amount to no more than speculation. 

They offered no drift model that had been tested, cited no studies 

9 Pence, who personally investigated the incident, was likewise unable 

to identify any “consistent pattern” or “drift pattern” of crop damage over this 

large area.
20

supporting their analysis, offered no reasoned discussion of the potential 

rate of error of their analysis, gave no indication that their approach to 

understanding aerial drift had been accepted in the scientific 

community, and could point to no non-judicial use of their methods. 

Robinson, 923 S.W.2d at 557. Thus, none of the Robinson factors are 

present, and the plaintiffs offer no alternative basis on which a court 

could find that their expert testimony on aerial-drift patterns is 

scientifically reliable. Just as in Robinson, the experts failed to present 

a scientifically valid model that could explain why there was “no 

consistent pattern of damage to the trees,” or in this case, the cotton 

crops. Id. at 551.

We do not suggest that precision of proof is required in such a 

case. Nor do we suggest a rigid requirement that such cases must 

always be proved with scientific modelling of the aerial-drift pattern or 

with any other precise category of evidence. But it defies reason to 

suggest that Helena’s aerial application of Sendero landed in roughly 

equal quantities on all 111 fields scattered across hundreds of square 

miles of Mitchell County. Some scientific attempt to model where the 

Sendero probably drifted, in what amounts, and why, could at least have 

provided rational estimates of how much of Helena’s Sendero, if any, 

reached these scattered fields. This information might enable the 

plaintiffs to establish that Helena’s Sendero substantially contributed 

to their losses across the entire area. Or it might narrow the area for 

which the plaintiffs can obtain recovery. Either way, assignment of 

liability to Helena could be based on a rational analysis bearing some 

indicia of reliability—not on the kind of assumptions and speculation we 
21

have repeatedly deemed insufficient. See, e.g., Marathon Corp. v. 

Pitzner, 106 S.W.3d 724, 729 (Tex. 2003); Cooper Tire, 204 S.W.3d at 

801–07; Burroughs Wellcome Co. v. Crye, 907 S.W.2d 497, 499–500 (Tex. 

1995).10

D.

A scientific model of the aerial drift—which the plaintiffs’ experts 

did not attempt to offer—could also have provided evidence on another 

important facet of causation in toxic-exposure cases: the dosage. We 

have often articulated the requirement in similar cases that the plaintiff 

establish with evidence the dosage required to produce the alleged 

injury. For example, in Robinson, we held that an expert’s testimony 

regarding contamination of pecan trees by fungicide was unreliable 

because the expert had “no knowledge as to what amount or 

concentration of [contaminants] would damage pecan trees.” 923 

S.W.2d at 559. Similarly, in Cooper Tire, we held that an expert’s theory 

that a tire suffered a manufacturing defect because of wax 

contamination was unreliable, in part because the expert “conducted 

nothing in the nature of a quantitative analysis of wax contamination, 

such as calculating the amount of wax deposited on the skim stock or 

10 We do not purport to be aware of all possible methods of proof in cases 

such as this one. By suggesting that the plaintiffs might have raised a genuine 

fact issue on causation by proffering additional types of evidence, we do not 

hold that all plaintiffs in spray-drift cases must proffer such evidence to 

survive summary judgment.
22

the amount of wax necessary to cause a tire malfunction.” 204 S.W.3d 

at 802.11

Later, in Borg-Warner Corp. v. Flores, we observed: “One of 

toxicology’s central tenets is that ‘the dose makes the poison.’” 232 

S.W.3d 765, 770 (Tex. 2007). We rendered judgment for the defendant 

because “absent any evidence of dose, the jury could not evaluate the 

quantity of respirable asbestos to which [the plaintiff] might have been 

exposed or whether those amounts were sufficient to cause asbestosis.” 

Id. at 771–72. Still later, in Bostic, we required proof of dose in 

mesothelioma cases, even though “relatively minute quantities of 

asbestos can result in mesothelioma.” 439 S.W.3d at 338. The Court 

held that “proof of ‘some exposure’ or ‘any exposure’ alone will not suffice 

to establish causation.” Id. Instead, “the dose must be quantified” 

because “[t]he essential teaching of Flores is that dose matters.” Id. at 

353, 360; see also Abraham v. Union Pac. R.R., 233 S.W.3d 13, 21 (Tex. 

App.—Houston [14th Dist.] 2007, pet. denied) (“Knowledge of the extent

of exposure to a potentially harmful substance is essential to any 

reliable expert opinion that the particular substance caused a disease.”) 

(emphasis added).

Just as it was no answer in Bostic to say that any exposure to 

asbestos can harm a person, it is no answer here to say that any 

exposure to Sendero can harm cotton plants. Sendero’s product label 

says that it is toxic to broad-leaf plants, which include cotton. And 

11 See also Pollock, 284 S.W.3d at 820 n.33 (“[A]ny agent, even tap 

water, may produce a toxic effect at a sufficiently high level of exposure,” while 

“even the deadliest poison is harmless at a sufficiently low level of exposure.”).
23

Rosenfeld opined that exposure as diffuse as ten parts per billion could 

harm cotton. But there is simply no evidence at all in this case about 

the amount of Helena’s Sendero that is alleged to have landed on the 

plaintiffs’ crops miles away from the Spade Ranch. Halfmann conceded 

that he had not “reconstructed how much Sendero drifted to any specific 

cotton field.” Nor is there any evidence that the unspecified amount of 

Sendero alleged to have landed on these fields was sufficient to make 

Helena’s Sendero application a substantial factor in the lost crop yields 

suffered by the plaintiffs.

Crucially, while it is undisputed that very small amounts of 

Sendero can damage cotton plants, no evidence was proffered indicating 

how much exposure would be required to substantially contribute to the 

lost crop yields suffered by the plaintiffs. In fact, two of the plaintiffs’ 

experts acknowledged that cotton plants showing signs of herbicide 

damage do not necessarily end up suffering reduced yield. According to 

Carrillo, “It could go either way. . . . They could or could not [have 

diminished yield].”

12 And none of the plaintiffs’ experts knew how much 

exposure to Sendero would cause reduced crop yield.

The plaintiffs do not seek recovery for wilted leaves in July. They 

seek recovery for reduced cotton harvests months later, long after the 

application of Sendero to the Spade Ranch. The damaged crops were 

harvested and sold, although they did not produce the volume of cotton 

desired. Whether Helena’s airborne Sendero was a substantial factor in 

12 Rosenfeld also acknowledged that exposure to clopyralid and 

resulting physical symptoms in cotton plants do not necessarily result in yield 

losses, especially at low levels of exposure.
24

causing the plaintiffs’ lost yield depends in part on how much Sendero 

landed on the crops. It also depends on the presence of other factors 

contributing to reduced yields, such as unfavorable weather (for which 

the farmers made insurance claims seeking recovery of the same losses). 

Without knowing how much Sendero exposure was required to produce 

the plaintiffs’ injuries and without a reliable estimate of how much 

Sendero landed on the fields, the factfinder could not even begin to 

reasonably determine whether Helena’s Sendero—rather than 

something else, such as weather or other herbicides—caused the losses.

E.

This brings us to the question of plausible alternative causes. We 

have often said in similar cases that the plaintiff bears the burden to 

account for such causes. “We recognized in Havner, generally, that ‘if 

there are other plausible causes of the injury or condition that could be 

negated, the plaintiff must offer evidence excluding those causes with 

reasonable certainty.’” Bostic, 439 S.W.3d at 350 (quoting Havner, 953 

S.W.2d at 720); accord JLG Trucking, LLC v. Garza, 466 S.W.3d 157, 

162 (Tex. 2015); Transcon. Ins. Co. v. Crump, 330 S.W.3d 211, 218 (Tex. 

2010). And in Robinson, we observed that an expert’s “failure to rule 

out other causes of the damage renders his opinion little more than 

speculation.” 923 S.W.2d at 559; see also Cooper Tire, 204 S.W.3d at 

807–08.

Alternative causes need not necessarily be ruled out entirely, 

however. In Bostic, we explained that in cases where multiple causes 

might have contributed to the injury, the expert does not have to 

completely eliminate the other causes as possible contributors. Instead, 
25

the analysis of alternative causes must be sufficient for the factfinder to 

reasonably conclude that the defendant’s conduct was a “substantial 

factor” in causing the injury. Bostic, 439 S.W.3d at 350–51. Nor must 

the plaintiff negate every conceivable alternative cause imagined by the 

defendant or the court. The testimony need only account for “other 

plausible causes raised by the evidence.” Transcon. Ins. Co., 330 S.W.3d 

at 218 (emphasis added).

Here, the evidence clearly indicates the plausibility of two 

alternative causes—weather and other herbicides. First, none of the 

experts accounted at all for the possible effect of weather on the reduced 

crop yields. On this record, the undisputed fact that many of the 

plaintiffs applied for insurance benefits for losses caused by weather 

confirms the need for their experts to account for this plausible 

alternative explanation for their losses. But the expert testimony makes 

no attempt to carry this burden.

Second, the record indicates that there could have been any 

number of other herbicide applications in the area, including efforts by 

individual property owners or by oil and gas operators. Halfmann 

acknowledged that herbicides other than Sendero are commonly used in 

the area during the summer. Most importantly, the record shows that 

there was another aerial Sendero application in the area. The record 

contains no indication that the experts investigated or analyzed the 

alternative reasons that clopyralid would have been detected in the 

tested fields—or that herbicide damage would have been visually 

observed—other than because of Helena’s use of Sendero. 
26

The plaintiffs’ evidence thus fails to account for two plausible 

alternative causes—weather and other herbicides—either of which 

might wholly explain the damage or render the defendant’s contribution 

trivial. Bostic, 939 S.W.3d at 351 (recognizing “that a defendant’s trivial 

contribution to multiple causes will not result in liability”).

In an effort to rule out other applications of clopyralid-containing 

herbicides as alternative causes, Carrillo and Halfmann observed that 

Helena’s application in early July 2015 was the only application large 

enough to cause the heavy losses alleged by the plaintiffs. This idea—

that only Helena’s large application of Sendero on a windy day could 

account for the widespread losses alleged—appears throughout the 

plaintiffs’ evidence and argument. But this approach largely assumes 

the matter to be proved. If we assume that all the reduced crop yields 

claimed in all the plaintiffs’ scattered fields had one source, then 

Helena’s application of Sendero in July 2015 is perhaps a likely culprit 

(although weather remains a possibility, and the plaintiffs’ experts 

made no attempt to account for it). The law does not permit this 

assumption, however.

Instead, the law acknowledges the reality that an injury may 

have many plausible sources, and it puts the burden on plaintiffs to 

proffer evidence accounting for plausible alternative causes other than 

the defendant’s conduct. When an injury may have multiple

contributing causes, the plaintiff must at least show that the defendant’s 

conduct was a substantial factor in causing the injury, taking into 

account any plausible alternative causes raised by the evidence. Bostic, 

439 S.W.3d at 350–51; Transcon. Ins. Co., 330 S.W.3d at 218. Here, the 
27

plaintiffs’ experts failed altogether to account for the potential 

contribution of plausible alternative causes—such as other herbicides or 

weather—to the plaintiffs’ reduced crop yields.13

The plaintiffs cannot account for plausible alternative causes of 

reduced cotton harvests in the fall and winter merely by demonstrating 

crop damage in July.14 There must instead be an affirmative showing 

13 Carrillo acknowledged that expert testimony in this case would need 

to exclude “other sources for the possible damage that the plaintiffs are 

alleging in this case” but that he did not do so. Rosenfeld testified that he did 

not know whether other applications of herbicides containing clopyralid could 

have been responsible for the damage to the plaintiffs’ crops. Halfmann 

testified that he had not personally excluded other causes but that he relied on 

TDA inspector Pence in that regard. None of the plaintiffs’ experts conducted 

an independent study or systematic review of other applications of herbicides 

during the relevant time period that might account for the plaintiffs’ reduced 

harvest. Instead, they relied on Pence’s TDA report. In this regard, Pence’s 

report cannot fairly be characterized as scientifically reliable evidence. Pence 

testified that his investigation indicated a possibility, as opposed to a 

probability, of crop damage in Mitchell County that could be tied to Helena’s 

application of Sendero. The only effort he made to eliminate other sources of 

the crop damage, over an area comprising hundreds of square miles, was to 

“drive up and down [four] roads looking for effects” from other applications and 

to ask some of the farmers if they saw anything. He did not meet with all the 

farmers or look into herbicide use by oil and gas operations in the area. 

Moreover, he ignored a TDA computerized database known as the PIER 

System, which tracks herbicide applications. Pence’s investigation cannot be 

characterized as a scientific effort to account for other herbicide applications, 

much less weather. Importantly, Pence made no attempt to determine the 

cause of the plaintiffs’ reduced crop yields later in the year. To be fair, such 

analysis was outside Pence’s job description. The burden was on the plaintiffs 

and their attorneys to obtain expert testimony explaining the effect of the 

alleged Sendero exposure in July 2015 on crop yields several months later, 

taking into account other plausible explanations for reduced yield, such as 

weather or other herbicides.

14 Again, the experts acknowledged that observed herbicide damage will 

not necessarily result in reduced crop yield. See supra at 23–24.
28

that the defendant’s conduct was a substantial factor in causing the 

reduced crop yield at harvest time, notwithstanding plausible 

alternative explanations. Any such proof is lacking here. Other than 

the experts’ say-so, the record is silent regarding the extent of the causal 

connection between the crop damage observed by Pence and the farmers 

in July and the reduced crop yield several months later. This “analytical 

gap” in the causal chain between the allegedly tortious conduct and the 

damages suffered requires summary judgment for Helena. See Gharda, 

464 S.W.3d at 349; Ramirez, 159 S.W.3d at 912; Gammill, 972 S.W.2d 

at 727.

III.

For these reasons, the evidence of causation offered by the 

plaintiffs fails to raise the genuine issue of material fact necessary to 

survive summary judgment. The court of appeals’ judgment is affirmed 

in part and reversed in part, and a take-nothing judgment on all claims 

is rendered.

James D. Blacklock

Justice

OPINION DELIVERED: March 3, 2023