Contents - Faperta

48 Biotechnological Approaches for Pest Management and Ecological Sustainability
FIGURE 3.3 Screening for resistance to brown planthopper, Nilaparvata lugens in rice under greenhouse
conditions.
avoid the build up of pathogen infections such as bacteria, fungi, protozoa, and viruses in
the insect colony.
Infestation Techniques
Standardization of techniques to infest the material at the susceptible stage with uniform
insect density is essential for successful evaluation of the test material under greenhouse
or fi eld conditions. Several techniques have been used for infestation and evaluation of
the test material in the fi eld (Smith, Khan, and Pathak, 1994; N. Panda and Khush, 1995)
(Table 3.2). While devising techniques to infest the test material, it is important to take into
consideration the:
• Stage of the insect and application procedure;
• Number of insects required and time of infestation;
• Number of infestations;
• Cannibalism among the individuals of the same species; and
• Susceptible stage of the crop and the site of infestation.
Efforts should be made to obtain uniform infestation at the most susceptible stage of the
crop in a manner closer to the natural infections. The amount of food available to the
insects and the insect density also infl uence the expression of resistance to insects, and
therefore, efforts should be made to use optimum and uniform infestation to result in
maximum differences between the resistant and susceptible genotypes (Sharma and
Lopez, 1993). Adults, eggs, or the fi rst-instar larvae can be spread uniformly in the test
material by hand or by mixing them with an inert carrier (Smith, Khan, and Pathak, 1994).
Adults can also be released on the test material inside cages (Sharma et al., 1992). Eggs are
released into the plant whorl or egg masses stapled on to the underside of the leaves
(Davis, 1985). Eggs can also be mixed in a liquid carrier such as agar-water and dispensed