Foreword - CCS HAU, Hisar

difficulty is to relate the number caught, particularly if the insects caught are only males, to
the actual pest life cycle, level of pest attack, the best time to apply a control, and crop
yield loss.
Sweep net : Sweeping can give repeatable results if the diameter of the net opening
and the number, extent, and frequency of sweeps are constant. The method was analyzed
by Ruesink and Haynes (1973).
Suction traps : Trapping or collecting insects by air suction is useful where attraction
to light or chemicals is of no use and where motor, mains, or battery electric power is
available. Continuous sampling at different levels above the crop can give valuable indications
of when, which and how many pests will attack
Light traps : If an oil, gas pressure, or electric light source is available, a light trap is
valuable for monitoring relative and absolute pest numbers and the seasonal appearance of
many species of moths, hoppers, and beetles (Rabb and Kennedy 1979, Bouden 1982).The
strength, wavelength, and direction of the light, the weather, and the presence of other light,
including moonlight (Verheijen 1960), are important. Some traps use ultraviolet or black
light, have a timing mechanism, or are daylight activated, and are equipped with a protective
roof, electrified vanes, or a suction pump.
Insecticide (e.g. dichlorvos) and something to prevent damage to the insects should be
placed in the trap container. A serious disadvantage is that the large, nonspecific catches
often demand some sort of sample divider (Shepard 1984).
Pitfall traps : In dry areas, smooth-sided plastic pots level with the soil surface will
collect mobile ground insects, predators, etc. They need frequent attention and protection
from flooding, birds, and ants.
Shelter traps and emergence traps : Some animals may be trapped and counted by
collecting them under some form of shelter (for example, termites under sheets of paper
[McMahen and Watson 1977]). Insects emerging from the soil can be caught using an inverted
funnel with a collecting tube at the top.
Mark, release, and recapture : If marking does not alter behavior, insects or other
animals can be marked, released, and recaptured. Populations can be estimated using the
Lincoln Index :
Number marked and released x total number caught
Population =
Number marked caught
The method used depends on whether pests are removed or replaced, and on survival
and migration (Blower et al 1981). Marking can be with combinations of paint spots, external
coloring or UV fluorescent dust, internal dye, or radioactive, bacterial, or genetic markers.
INDIRECT ASSESSMENT METHODS
It is often easier, quicker, and cheaper to count or estimate the indirect effects of pests.
The difference between incidence (damage or number of damaged plants) and intensity or
severity (degree or extent of damage) should be noted. Incidence is a discrete measure,
intensity is continuous and finite.
Whole plants. The number or percentage of missing or damaged plants is often recorded.
Soil pests, cutworms, stem borers, etc., may cause loss of plant stand. Errors in damage
assessment may occur if the number of missing plants is not taken into account.
42