Biology Reference
In-Depth Information
9.4.3 Pest Control
More than a hundred insect species live or feed on different structures of the
numerous Helianthus species. Along with birds, mammals, nematodes and
acari, which have caught the attention of recent investigations, insects
constitute a highly heterogeneous species group ( Table 9.4 ) . At least three of
these sunflower enemies would be restricted to the North American
Helianthus and have specific natural controllers (Cantamutto and Poverene
2007), coleoptera Zygogramma exclamationis being the important one. In
Europe and South America, most of the insects that affect sunflower are
unspecific (Charlet et al. 1997) the main cosmopolitan one being Helicoverpa
armigera. Sunflower lepidoptera pests constitute a wide group of more than
30 polyphage species that feed mainly on aerial parts of the plants (Rogers
1992) and affect yield by decreasing the photosynthetic area. Another
sunflower constraint caused by Arthropoda is failure of stand establishment
due to soil larvae, mainly of Coleoptera. These herbivors, which feed on
seedling stems and roots at different levels, all correspond to polyphagous
species, Agriotes being the most widespread genus.
Some animal constraints have only a regional importance, like birds
(i.e., blackbird, http://www.sunflowernsa.com ), acari, and nematodes that are
very harmful in some crop regions of America and Asia. Novel pests originate
from changes in the production systems. In Argentina with the increase in
no-till areas, two previously unnoticed snails of the genus Deroceras
(Carmona 2001) and crustaceous of the genera Armadillidium , Porcellio and
Balloniscus (Ves Losada et al. 2007) have recently become limiting factors for
the sunflower crop.
Classical sunflower breeding techniques have succeeded in achieving
insect resistance. The European moth ( Homoeosoma nebulella ), which was
once the main constraint on the dissemination of this crop in Europe (Chen
and Welter 2003) and the tobacco caterpillar ( Spodoptera litura ), an important
crop limitation in warm regions (Sujatha and Lakshminarayana 2007) and
possibly other pests could be controlled through resistant sources from
wild species (Rogers 1992; Charlet et al. 2007).
However, the most frequent methods used for pest control in sunflower
involve the use of pesticides. A number of chemical products are
recommended to control insects that reduce crop stand. Biotechnology could
improve this control by helping in developing insect-resistant GM sunflower.
Sustainable management calls for complete knowledge of the biology of the
target pest and its relationship with other components of the agro-ecosystem.
The options offered by genetic engineering include GM crops that express
gene fragments from insecticide proteins of Bacillus thuringensis (Bt
endotoxins including Cry1Aa, Cry1Ab, Cry1Ac, Cry1Ca, Cry1Fa, Cry3Aa,
and others), the Vigna unguiculata trypsin inhibitor (CpT1), lectins, and other
 
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