1.PG Economics Ltd studies
2.National Center for Food and Agriculture Policy  (NCFAP) studies

NOTE: The recent report, 'Impacts of Genetically Engineered Crops on Pesticide Use: The First Thirteen Years', by Charles Benbrook has stirred a lot of interest and some attempted rebuttals. All of the latter - from the Biotechnology Industry Organisation down, seem to draw heavily on the findings of the UK consultancy PG Economics Ltd.

For instance, an article published by the pro-GM lobby group Truth About Trade states, "It's possible to point to statistics that say the exact opposite [to the Benbrook study]. PG Economics Ltd., a well-regarded English consulting firm, recently issued its own findings and said that the use of pesticides on global biotech acreage has dropped almost 800 million pounds--or nearly 9 percent--during the same period."

Curiously, although the Truth About Trade article brands Benbook's study "activist-sponsored", it fails to mention that PG Economics work in this area is almost invariably funded by the biotechnology industry. It also fails to mention, possibly because like other critics the author failed to read the actual study, that Benbrook includes a review of PG Economics' work (see below - item 1) within his study.

What's apparent from Benbrook's review is the extreme lengths to which the PG Economics' analysts have had to go to come up with their conclusions. This includes such "creative and highly questionable methodological strategies" as disavowing their own "data-driven estimates". (item 1)

This is not the first time PG Economics has been accused of methodological creativity in achieving their results.

Any such creativity might perhaps owe its origin the passionate commitment they, and those around them, display towards GM crops. According to one press report:

"A presentation by Graham Brookes, director of the England-based PG Economics Limited, showed hard evidence of the overwhelmingly positive economic and environmental impacts of the crops. Mind you, this is a man whose company gets a paycheck from such pro-GM trade associations as CropLife International and Green Biotech Europe, and who summed up his view of the Indian environmental activist Vandana Shiva with the couplet 'bloody idiot.'"

Incidentally, Brookes' co-director at PG Economics, Peter Barfoot, heads an organisation with the motto: "Serving the biotechnology industry".

It's sometimes claimed that some of PG Economics work has been "peer-reviewed". But such claims are based on publication in the Journal of Agrobiotechnology Management & Economics - otherwise known as AgBioForum. AgBioForum has such enthusiastic GM proponents as C. S. Prakash on its editorial board and is funded by the Illinois-Missouri Biotechnology Alliance who say their purpose is "to fund biotechnology research... directed at expanding the volume of profitable businesses in the US food and agricultural sector".
 
Below we include Benbrook's review of PG Economics' studies, and also his review of studies by the National Center for Food and Agriculture Policy (NCFAP), whose work PG Economics draw on. (Note that in the Benbrook study he reviews the work of NCFAP ahead of that of PG Economics - we've reversed the order).

To access the Benbrook study:
Full report - pdf (3.68 MBs, 69 pages)

Executive Summary - pdf (1.44 MBs, 15 pages)
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1. PG Economics Ltd Studies

From Dr Charles Benbrook, Impacts of Genetically Engineered Crops on Pesticide Use in the United States: The First Thirteen Years, November 2009

A UK based consulting firm, PG Economics Ltd., has carried out several studies of GM crops funded by the pesticide and biotechnology industries. Their latest was released in May 2009. The PG Economics report uses methods and sources similar to NCFAP [dealt with earlier - see below], and claims its estimates are based on "the average performance and impact recorded in different crops."

The PG Economics report estimates a 4.6% reduction worldwide in herbicide use attributable to GM crops from 1996 through 2007 (the first 12 years of commercial use). This report [Benbrook's] estimates that GM HT [Herbicide Tolerant] corn, soybeans, and cotton have increased herbicide use in the U.S. by 382 million pounds over 13 years, or by about 10% (NASS [the USDA's National Agricultural Statistics Service] reports that 3.82 billion pounds of herbicides applied to these three crops from 1996-2008). It is worth noting that the increase in 2008 the extra year covered by this analysis was 100 million pounds, or about 26% of the total increase over the 13 years.

The methodology in the PG Economics report is worth a closer look. HT soybeans are by far the most important GM crop in the U.S. in terms of impacts on pesticide use, and so the focus herein is on the PG Economics analysis of herbicide use on conventional and HT soybeans.

The authors begin by noting that there are two primary sources of data on pesticide use in the U.S. NASS surveys and private farm-level surveys (survey data from DMR Kynetec was used in the PG Economics report).  

Their Table 33 reports herbicide use on HT and conventional soybeans for 1998 through 2007 in the U.S., based on Kynetec survey data. In every year, herbicide use was higher on HT soybeans than conventional soybeans. The margin was typically less than 0.2 pounds until 2002, when the margin increased to around 0.3 from 2003-2007.
 
Estimates of herbicide use on HT soybean acres as reported in the PG Economics report and this analysis differ modestly, and are accounted for largely by the rate per crop year of glyphosate herbicides. Likewise, the PG Economics and this report's estimates of total herbicide use on conventional soybean acres, and the differences between HT and conventional acres, are relatively close for 1998 through 2004. The Kynetec dataset then projects increases in the total rate of herbicide application on conventional acres from 2004 through 2007, despite the continued trend toward greater reliance on relatively low-dose herbicides, as evident in the projections based on NASS data.

This deviation in estimates of herbicide use on conventional soybeans accounts for this report's progressively larger margin of difference in herbicide use rates on HT in contrast to conventional soybean acres.

Despite some differences, it is significant that the industry-sponsored Kynetec survey, as reported by PG Economics, supports the same basic conclusion as this report HT soybeans have increased herbicide use by a substantial and growing amount.

But curiously, right after reporting the Kynetec results in Table 33, the authors of the PG Economics report state:

"The comparison data between the GM HT crop and the conventional alternative presented above is, however, not a reasonable representation of average herbicide usage on the average GM HT crop compared with the average conventional alternative for recent years."

The PG Economics analysts disavow their own data-driven estimates, asserting that herbicide use is lower on conventional soybean acres in the Kynetec dataset because the majority of farmers planting conventional soybeans must be among those facing the lightest weed pressure. This creative argument, however, is incompatible with the pattern of adoption of HT soybeans across the states. Since 2006, the rate of adoption of HT soybeans varies modestly between states from 81% to 97%, with no clear pattern between states with relatively low weed pressure (Minnesota, South Dakota) and states with much higher levels of weed pressure (Mississippi, Arkansas).

After rejecting the Kynetec survey findings that were based on real data, the PG Economics team then turns to another source for supposedly more reliable estimates the National Center for Food and Agricultural Policy [see below]. The PG Economics team revises its soybean herbicide use projections drawing on NCFAP's faulty simulations, and reaches the basic finding of a 6.8% reduction in herbicide use as a result of HT soybeans.

Similarly creative and highly questionable methodological strategies are employed by the PG Economics team in projecting the impacts of other GE crops on pesticide use. Like the NCFAP, the PG Economics team never explains the discrepancies between their estimates and those based on NASS data.

NB: The findings of the PG Economics report were featured at the Biotechnology Industry Organization (BIO) 2009 conference and subsequently used by most biotechnology and pesticide industry trade associations in public relations efforts designed to promote awareness of the benefits of GE crop technology.  Note that in [a] posting [on the BIO website, 21 May 2009] by Michael Phillips, BIO Vice President for the Food & Agriculture program, the PG Economics report is highlighted as a "counter" to the 2004 UCS report on the impacts of GM crops on pesticide use over the first nine years of commercial use.
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2.National Center for Food and Agriculture Policy  (NCFAP) studies

Several studies by the National Center for Food and Agriculture Policy (NCFAP), an organization funded in part by the biotechnology industry, have addressed the impact of GM crops on pesticide use. The most recent report was released in November 2006 and projects impacts in crop year 2005.

NCFAP's general method is to simulate pesticide use on GM and non-GM crops by simply extrapolating from particular pest management systems recommended by university extension agents for adoption on all GM and non-GM crop acres. Such simplistic models are highly vulnerable to error, since actual pest management systems often are not the same as those recommended by university specialists.

NCFAP on corn

NCFAP estimates that GM HT corn was planted on 35% of corn acres in 2005, a considerably higher share compared to NASS's (the USDA's National Agricultural Statistics Service) corresponding figure of 26%. Based on this 35% figure, NCFAP estimates that GM HT corn reduced herbicide use by 21.8 million pounds in 2005, or about 0.8 pounds per acre.

This finding rests largely on two faulty assumptions that exaggerate the amount of herbicide applied to conventional/non-HT corn acres, which in turn inflates the “reduction” from a switch to HT corn.  These faulty assumptions relate to the extent and rate of use of two high-dose herbicides, atrazine and s-metolachlor/metolachlor, that are used on both HT and conventional/non-HT corn.

With regard to extent of use, NCFAP assumes that all non-HT corn farmers apply two premixed products: first, a mixture of the high-dose herbicides s-metolachlor and atrazine (preemergence), followed post-emergence by a product consisting of mesotrione, nicosulfuron and rimsulfuron. NASS data demonstrate clearly that the atrazine-metolachlor premix could not have been used by a majority of, much less all, farmers planting non-HT corn.   According to NCFAP, non-HT corn comprised 65% of national corn acres, while NASS reports that just 25% of all corn was treated with either s-metolachlor or metolachlor, so that at most 25% of corn acres were treated with this premix. At most, 38% of non-HT corn acres could have been treated with this high-rate premix.

NCFAP assumes that non-HT corn farmers apply the s-metolachlor/atrazine premix at 3.16 pounds of active ingredients per acre, and the low-dose post-emergence mix at 0.07 pounds per acre, for a total of 3.23 pounds per acre.  However, NASS reports that the average amounts of atrazine and s-metolachlor applied to all corn in the 2005 season were 1.13 and 1.35 pounds per acre, respectively.    Accordingly, the combined average rate of atrazine and s-metolachlor applied via the premix was at most 2.48 pounds of active ingredient per acre, much less than the 3.16 pounds assumed by NCFAP.

NCFAP projects that an average of 2.5 pounds of herbicides were applied on RR corn acres in 2005, resulting in a 0.73 pound per acre reduction (3.23 pounds on conventional acres, minus 2.5 pounds on RR acres). NCFAP would have projected a 0.02 pound increase on HT acres had it used the more realistic NASS application rates for atrazine and s-metolachlor on conventional corn. The methodology in this report projected a 0.01 pound reduction in per acre herbicide use on HT acres in 2005.

NCFAP on HT soybeans

In the case of soybeans, NCFAP both underestimates herbicide use on HT acres and overstates the amount applied to conventional acres.  These faulty assumptions result in a simulated and illusory “reduction” of 20.5 million pounds nationally from the planting of HT soybeans in 2005.

NCFAP wrongly assumed that one application of glyphosate sufficed for over 80% of Roundup Ready soybean acres, resulting in a simulated 1.18 glyphosate applications to the average RR soybean acre for the year.  In contrast, NASS reported an average of 1.5 applications of glyphosate (28% higher), a figure that reflects the need for two or more glyphosate applications to control resistant weeds in many states. Similarly, NCFAP’s estimate of total herbicide applied to RR soybeans 1.03 pounds per acres per year does not even match the annual NASS figure for glyphosate alone, which is 1.1 pounds per acre, much less account for non-glyphosate herbicides applied to RR soybeans.

NCFAP assumes, for reasons not explained, that herbicides in addition to glyphosate were applied to RR soybeans in just one state (Iowa).  In Iowa, NCFAP assumes that soybean farmers apply 0.19 pounds per acre of Canopy (a premix of chlorimuron and metribuzin), in addition to one application of glyphosate.  In contrast, this report (Benbrook’s) more realistically estimates that non-glyphosate herbicides were applied to RR soybean acres at an average rate of 0.12 pounds per acre in 2005.

NCFAP also vastly overstates the amount of herbicides applied to conventional soybean acres in 2005, assuming average total applications of 1.35 pounds per acre (all presumed to be non-glyphosate herbicides).  This presumed rate for herbicides applied to conventional soybean acres is more than twice the rate of 0.59 pound per acre on conventional soybeans estimated in this study, based on NASS data.  NCFAP’s estimate of average herbicide use on conventional soybeans is clearly out of step with the trend toward lower-dose herbicides, some of which are applied at rates well below 0.1 pound per acre.

If NCFAP had used NASS data to work out herbicide use on RR and conventional soybean, it would have arrived at a result much closer to the one in this report: an estimated increase in herbicide use of 41.5 million pounds in 2005 due to the planting of RR soybeans.