Contents - Faperta

6 Biotechnological Approaches for Pest Management and Ecological Sustainability
and cropping systems. The most common predators include Chrysopa, Chrysoperla, Nabis,
Geocoris, Orius, Polistes, and the species belonging to Pentatomidae, Reduviidae,
Coccinellidae, Carabidae, Formicidae, and Araneida (Zalucki et al., 1986; King and Coleman,
1989; Romeis and Shanower, 1996). Some predators have been used in augmentative release
studies, notably Chrysoperla carnea (Stephen). Although effective in large numbers, the high
cost of large-scale production precludes their economic use as a biological control (King
and Coleman, 1989). Naturally occurring predators play a major role in keeping the insect
pest populations below ETLs. Coccinellids and chrysophids have been used successfully
for biological control of insect pests under greenhouse conditions, and in some situations,
under fi eld conditions.
Increasing genetic diversity also helps to increase the abundance and effectiveness of generalist
predators (Sunderland and Samu, 2000; Schmidt et al., 2004). Some natural enemies
may be more abundant in polycultures because of the greater availability of nectar, pollen,
and diversity of prey (Bugg, Ehler, and Wilson, 1987) for a longer period of time (Topham
and Beardsley, 1975). Populations of coccinellid beetles (Coccinella transversalis Fab. and
Adalia bipunctata L.), lace wings (Chrysopa spp.), reduviid and pirate bugs [Coranus triabeatus
(Horvath)], and spiders (Lycosa spp. and Araneus spp.) have been found to be signifi cantly
greater in maize-cowpea intercrop than on cotton alone. Greater numbers of Geocoris spp.
and other predators have been recorded on knotweed than on other weed species, which was
attributed to availability of fl oral nectar and of alternate prey (Bugg, Ehler, and Wilson, 1987).
Greenbug, Schizaphis graminum (Rondani), on strips of sorghum interplanted in cotton has been
found to support large numbers of the coccinellid predator, Hippodamia convergens Guerin-
Meneville and other predators (Fye, 1972). Abundance of the predatory mite, Meta seiulus
occidentalis (Nesbitt) was greater in plots adjacent to alfalfa intercropped in cotton (Corbett
and Plant, 1993). Mulching of the soil surface with crop residue also increases the abundance of
the generalist predators (Altieri, Wilson, and Schmidt, 1985; Schmidt et al., 2004).
Entomopathogenic Bacteria
Several entomopathogenic bacteria play a major role in controlling insect pests under
natural conditions. Formulations based on B. thuringiensis have been marketed since the
1950s. There are 67 registered Bt products with more than 450 formulations. The major
boost to the production and use of Bt products came with the discovery of the HD-1 strain
of Bt subspecies kurstaki, which is effective against a large number of insect species
(Dulmage, 1970). Several commercial products such as Thuricide ® , Dipel ® , Trident ® ,
Condor ® , and Biobit ® are marketed worldwide. There are several subspecies of this
bacterium, which are effective against lepidopteran, dipteran, and coleopteran insects.
Formulations based on Bt account for nearly 90% of the total biopesticide sales worldwide
(Neale, 1997), with annual sales of nearly US$90 million (Lambert and Peferoen, 1992). Bacillus
israeliensis L. has been used extensively for the control of mosquitoes. Narrow host range,
necessity to ingest the Bt toxins by the target insects, ability of insect larvae to avoid lethal
doses of Bt by penetrating into the plant tissue, inactivation by sunlight, and effect of plant
surface chemicals on its toxicity limit its widespread use in crop protection (Navon, 2000).
There may be a limitation on the use of Bt-based products in crops or areas where transgenic
plants with Bt toxin genes have been deployed as a strategy for resistance management.
Baculoviruses
Baculoviruses are regarded as safe and selective pesticides. They have been used against
many insect species worldwide, mainly against lepidopteran insect pests. The NPVs exist