Contents - Faperta

8 Biotechnological Approaches for Pest Management and Ecological Sustainability
limited to certain niches and insect species. There is a need to improve culturing techniques,
formulations, quality, and the application technology.
Cultural Control
The need for ecologically sound, effective, and economic methods of pest control has
prompted renewed interest in cultural methods of pest control. The merit of many of the
traditional farm practices has been confi rmed by learning why farmers do what they do.
But some practices still remain to be thoroughly investigated and understood. A number
of cultural practices, such as selection of healthy seeds, synchronized and timely sowing,
optimum spacing, removal of crop residues, optimum fertilizer application, and regulation
of irrigation, help in minimizing the pest incidence. A number of crop husbandry practices
that help reduce pest damage can be quite effective under subsistence farming conditions
and these involve no additional costs to the farmers, and do not disturb natural enemies of
the insect pests and the environment.
Date of Sowing and Planting Density
Sowing time considerably infl uences the extent of insect damage. Normally, farmers plant
with the onset of rains. Synchronous and timely or early sowing of cultivars with similar
maturity over large areas reduces population build up of insect pests and the damage they
cause. In Tamil Nadu, India, there is an old adage among the farmers, “inform your neighbor
before you plant sorghum lest his crop be destroyed by shoot fl y [Atherigona soccata
(Rondani)] and head bugs [Calocoris angustatus (Lethiery)].” Early and uniform sowing of
sorghum over large areas has resulted in reducing the damage by shoot fl y and sorghum
midge [Stenodiplosis sorghicola (Coqillett)] in Maharashtra, India. Early planting of pigeonpea
results in reduced damage by H. armigera (Dahiya et al., 1999). The traditional practice
of using a high seeding rate helps to maintain optimum plant stand and reduce insect
damage in cereals (Gahukar and Jotwani, 1980). Shoot fl y and midge damage in sorghum
is higher when plant densities are low (Sharma, 1985). Timely thinning of the crop also
helps to reduce pest damage.
Nutrient Management
The extent and nature of fertilizer application infl uence the crop susceptibility to insects.
In some instances, high levels of nutrients increase the level of insect resistance, and in
others they increase the susceptibility. An increase in nitrogenous and phosphatic fertilizers
decreases shoot fl y, A. soccata, and spotted stem borer, Chilo partellus (Swinhoe), infestation
in sorghum (Chand, Sinha, and Kumar, 1979), possibly by increasing plant vigor
(Narkhede, Umrani, and Surve, 1982). Plants treated with K and NK also suffer low shoot
fl y and borer damage in sorghum (Balasubramanian et al., 1986). Shoot fl y and stem borer
damage has been found to be greater in plots treated with cattle manure. This may be due
to the attraction of shoot fl ies to the odors emanating from organic manure. Application of
biofertilizer (Azospirillum sp.) increases the phenolic content of sorghum seedlings and
results in a decrease in shoot fl y damage (Mohan et al., 1987). Azospirillum also increases
the effectiveness of carbofuran for shoot fl y control (Mote, 1986). Application of potash
decreases the incidence of top shoot borer, Scirpophaga excerptalis (Walker) in sugarcane.
High levels of nitrogen lead to greater damage by the cotton jassid, Amrasca biguttula
biguttula Ishida. A change in nutrient supply also affects the resistance to greenbug,