Agriculture Reference
In-Depth Information
The profitability of GE seeds for individual farmers depends largely on
the value of the yield losses mitigated and the associated pesticide and seed
costs.
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GE adoption tends to increase net returns if the value of yield losses
mitigated plus the pesticide savings exceeds the additional GE seed costs.
Adoption of Bt crops increases yields by mitigating yield losses to pests.
Bt crops are particularly effective at mitigating yield losses. For example,
before Bt corn was commercially introduced in 1996, the European corn borer
was only partially controlled using chemical insecticides (Fernandez-Cornejo
and Caswell, 2006). Chemical use was not always profitable, and timely
application was difficult. Many farmers accepted expected yield losses of 0.4
to 3.2 bushels from this pest rather than incur the expense and uncertainty of
chemical control (Hyde et al., 1999). After the introduction of Bt corn,
adopters who had previously controlled corn borer infestations using
insecticides lowered their pesticide costs and increased their yields. Adopters
who had not previously treated European corn borer infestations with
insecticides achieved only yield gains (and may have incurred higher seed
costs).
In addition to improvements in background germplasm, Bt corn yields
have increased over time as new insect resistance traits have been incorporated
into the seeds and multiple (stacked) traits have become available (Fernandez-
Cornejo and Wechsler, 2012). For instance, upon commercial introduction in
1996, Bt corn seeds were only resistant to one type of pest: the European corn
borer. Since then, resistance to corn rootworms (2003) and corn earworms
(2010) has been introduced.
Most experimental field tests and farm surveys show that Bt crops
produce higher yields than conventional crops (table 4). Intuitively, Bt
adopters are more likely to obtain higher yields than nonadopters by
controlling insects and thus reducing yield losses to pests. The yield gain of Bt
crops has become larger in recent years as new Bt traits have been
incorporated into the seeds and multiple (stacked) traits have become
available. For example, ARMS data show that the yield gain by Bt corn
adopters relative to conventional varieties increased from 12.5 bushels per acre
in 2001 to 16 bushels in 2005 and 26 bushels in 2010 (table 5; Fernandez-
Cornejo and Li, 2005).
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The geographical distributions of Bt adoption rates
and average corn yields for 2010 are shown in figures 6 and 8, respectively.
