Contents - Faperta

346 Biotechnological Approaches for Pest Management and Ecological Sustainability
Coleomagilla maculata (DeGeer), O. insidiosus, and C. carnea (except those of C. maculata) did
not complete development on pollen diet, although pollen was provided to larvae for a
limited period of time (Pilcher et al., 1997). However, pollen contains relatively low amounts
of Bt toxin, and the larvae generally do not feed on pollen under natural conditions.
The concentration of Cry1Ab in pollen is very low (2.57 to 2.94 μg per gram dry weight) as
compared with that of the leaves (Koziel et al., 1993; Fearing et al., 1997). Only the adults
feed on pollen to supplement their diet for ovary maturation.
Diversity of the arthropod community in transgenic cotton has been found to be similar
to that in conventional cotton without spraying, but the Shannon’s index for total arthropod
community and neutral insect subcommunity in Bt cotton fi elds was signifi cantly
higher than in sprayed plots at the mid- and late-growing stages of cotton (Li et al., 2003;
Men, Ge, and Liu, 2003). Bt cotton may increase the numbers and stability of arthropods
in a cotton ecosystem and improve the management of insect pests. The diversity of the
arthropod community in Bt cotton fi elds is greater than that in conventional cotton, suggesting
that Bt cotton is highly favorable for integrated management of cotton pests (Wu,
Peng, and Jia, 2003). However, Cui and Xia (2000a, 2000b) observed that Bt transgenic cottons
resulted in a decrease in species abundance and numbers of individual species. In the
absence of cotton bollworm, H. armigera on transgenic cotton (the dominant pest in cotton),
the red spider mite and thrips become the dominant pests. Bt cotton was effective in
controlling H. armigera, but the populations of Aphis gossypii Glover, Thrips tabaci Lind., and
Lygus lucorum (Mayer-Dur) increased in Bt cotton fi elds under natural or chemical control
compared to that in the normal cotton fi elds (Sun et al., 2002). The population of Chrysopa
formosa Brauer increased in transgenic cotton fi elds, but that of predators such as Orius
minutus (L.), Deraeocoris punctulatus (Fallen), and several parasitoids decreased in transgenic
cotton fi elds. Seed treatment of transgenic cotton with imidacloprid resulted in an
increase in numbers of coccinellid beetles, C. septempunctata and Cheilomenes sexmaculatus
(Fab.); green lace wing, C. carnea; Lynx spider, Oxyopes javanus Thorell; orb spider, Argiope
minuta (Karsh); wolf spider, Lycosa pseudoannulata (Boes. and Str.); long-jawed spider,
Tetragnatha javana (Thorell); Neoscona theisi (Walch.); and Peucetia viridana (Stal) (Kannan,
Uthamasamy, and Mohan, 2004). The populations of nontarget insect pests were signifi -
cantly greater in transgenic cotton than those in normal cotton plots. Species diversity and
numbers varied between bivalent (cry1Ac CpTi) and univalent (cry1Ac) transgenic plots
(Sun et al., 2003). The population of A. gossypii, A. biguttula biguttula, and Bemisia tabaci
(Genn.) was lower by 33.0%, 50.6%, and 22.7%, in bivalent cotton than in univalent cotton,
respectively. However, the population of T. tabaci and L. lucorum was higher by 208.9 and
18.4%, respectively. The numbers of leafhoppers, A. biguttula biguttula; grey weevil,
Myllocerus sp.; red cotton bug, Dysdercus keonigii F.; and aphids, A. gossypii have been
found to be similar between the Bt transgenic and nontransgenic cotton (Sharma and
Pampapathy, 2006). However, damage by the bollworms, H. armigera and Earias vittella (F.)
was signifi cantly lower in transgenic cotton compared to nontransgenic cotton. There were
no apparent effects of transgenic cotton on the relative abundance of predatory spiders,
Clubiona sp. and Neoscona sp., coccinellid, C. sexmaculatus and the chrysopid, C. carnea
(Figure 11.2). However, the abundance of spiders, coccinellids, and chrysopids was very
low in insecticide-protected plots toward the end of the cropping season (Sharma,
Pampapathy, and Arora, 2007).
There were no differences in trap captures of major ground-dwelling coleopteran predators
such as carabids and staphylinids between Bt-and non-Bt potato fi elds treated with
weekly sprays of a microbial Bt-based formulation containing Cry3Aa, biweekly applications
of permethrin, early and mid-season in-furrow applications of systemic insecticides