Helena Chemical Company v. Robert Cox

Supreme Court of Texas
══════════
No. 20-0881
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Helena Chemical Company,
Petitioner,

v.

Robert Cox, et al.,
Respondents

═══════════════════════════════════════
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
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.

2
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,

3
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.

4
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.

5
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

6
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

7
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

8
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.’”

9
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

10
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;

11
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.

12
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

5See, 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

13
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-by-
field 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.”).

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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

15
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.

16
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.

17
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”).

18
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.

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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

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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.

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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.”).

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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.

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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,

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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.

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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

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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.
14Again, the experts acknowledged that observed herbicide damage will
not necessarily result in reduced crop yield. See supra at 23–24.

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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

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